Category Archives: Health

Everything You Always Wanted To Know About Sleep (But Were Too Afraid To Ask)

This post is by far, my most popular ever. Sick and tired of politics after the 2004 election I decided to start a science-only blog – Circadiana. After a couple of days of fiddling with the template, I posted the very first post, this one, on January 8th, 2005 at 2:53 AM and went to bed. When I woke up I was astonished as the Sitemeter was going wild (getting a couple of thousand hits was a big deal back then, but within a few days, this post got to about 60,000 visits)! This post was linked by BoingBoing and later that day, by Andrew Sullivan. It has been linked by people ever since, rediscovered over and over again, although the post is six and a half years old.
I decided to move the post from the old archives here without any editing. I hope my writing has improved since then. And beware that it is more than six years out of date. It is here, really, to show my first real scienceblogging post, the one that convinced me, due to positive response, to switch from political to science blogging. A piece of personal history, if you wish.

What are you doing up so late, staring at the computer screen reading this? For that matter, what am I doing up late writing this at 11pm? Are we all nuts?

Until not long ago, just about until electricity became ubiquitous, humans used to have a sleep pattern quite different from what we consider “normal” today. At dusk you go to sleep, at some point in the middle of the night you wake up for an hour or two, then fall asleep again until dawn. Thus there are two events of falling asleep and two events of waking up every night (plus, perhaps, a short nap in the afternoon). As indigenous people today, as well as people in non-electrified rural areas of the world, still follow this pattern, it is likely that our ancestors did, too.The bimodal sleep pattern was first seen in laboratory animals (various birds, lizards and mammals) in the 1950s, 60s and 70s, i.e, before everyone moved their research to mice and rats who have erratic (un-consolidated) sleep patterns. The research on humans kept in constant conditions, as well as field work in primitive communities (including non-electrified rural places in what is otherwise considered the First World) confirmed the bimodality of sleep in humans, particularly in winter.

Larks and Owls
There is a continuum of individual sleep patterns ranging from extreme “larks” who fall asleep at the first inkling of dusk but wake up before dawn, all the way to the extreme “owls” who stay up quite late and wake up once the day is in full swing, and of course everything in between. No matter where you are on this continuum, you tend to sleep more during the winter long nights than during the short summer nights.

The genetic basis of extreme “larkiness” has been elucidated. It is a mutation in a phosphorilation site on the protein product of the core-clock gene period (per). A phosphorilation site on a protein is a place where another protein may add a phosphate group. Phosphate groups are ubiquitous sources of energy in biology (remember ATP from high-school biology? That’s it!). Thus, an addition of the phophate may make it easier for the protein to react with another molecule. That other molecule may give it stability, or destroy it, or allow it to move to another part of the cell. In the case of period, it appears that lack of the phosphate group allows the protein to move into the nucleus sooner than normal where it blocks transcription of its own gene.

Of course, we are talking statistics here: hundreds or thousands of period proteins per cell, several thousand pacemaker clock-cells in the suprachiasmatic nuclei, plus trillions of peripheral clock-cells all over the body: each of these molecules has a statistical chance of moving back into the nucleus sooner than in a person without a mutation. Moving sooner into the nucleus means that the inherent (“freerunning”) period of the clock is shorter. In most people it is about 24-25 hours long (when measured in completely constant environmental conditions, i.e., no light-dark, temperature, sound, or social cycles). The “owls” have longer periods and “larks” have shorter periods. Period determines phase relationship between the internal clock and the environmental synchronizing cue (e.g., the light-dark cycle), thus longer the period of the clock, later the clock will trigger waking up in the morning or feeling sleepy in the evening, and vice versa. People like me go to bed at 4am and wake up at noon. People with the extreme lark mutation wake up at about 4am, but are real party poopers, snoozing at 7pm or so. The whole continuum is believed to be determined by similar small mutations in which just a single DNA base-pair is replaced in one of the clock genes (12 such clock-genes are known so far to operate in mammals).

During a normal night’s sleep, REM occurs every 90 minutes or so. As the night progresses, the REM episodes get longer and the non-Rem periods in-between become shorter (thus still adding up to 90 minutes) as well as shallower. Thus, the really deep sleep (e.g, Stage 3) occurs only during first 1-2 cycles early in the night. Lack of Deep Sleep results in tiredness. Usually adults wake up from REM (children do not), unless waking is forced (e.g., alarm clock). Research on relative roles of REM and NREM in consolidation of memory is very controversial (look for Jerome Siegel on Google Scholar). Growth Hormone surges during episodes of Deep Sleep, and falls during REM, and is almost undetectable during wakefulness.

In the morning, our body prepares us for waking by increasing blood levels of ACTH and cortisol (leading to preponderance of heart attacks at waking time). Our body temperature is the lowest just an hour or two before waking and highest an hour or two before falling asleep. If you feel a chill sometimes when you are up at strange times, it is because your clock is at a pre-waking (late-night) phase.

Melatonin is secreted only at night (circadian clock time) and is not dependent on sleep. However, bright light tends to reduce melatonin levels. In summer, nights are short, thus the duration of the melatonin “signal” is short. In winter, nights are long, thus the duration of the melatonin “signal” is long. The duration of the melatonin signal is the cue that the circadian clock (this is in mammals only) uses to detect season, i.e., the changes in photoperiod (daylength) – information important for timing of seasonal events, e.g., molting, migration, hibernation, reproduction. Humans are only mildly seasonal – our ancestors about 70 million years ago were living in little holes in the ground, were tiny, were nocturnal, were seasonal breeders, and were hibernators. Some traces of our ability to measure photoperiod are retained in “winter blues”, or Seasonal Affective Disorder (SAD). It is almost a form of hibernation.

Phase-disorders of the circadian clock (i.e., extreme larks or owls) can have a similar effect by tricking the melatonin signal (or the reading of the signal by the clock) into believing it is always winter, thus time to be depressed. Lithium treats depression by affecting the period (thus indirectly phase) of the circadian clock (both in vivo and in vitro). In bipolar disorder, manic episodes are characterized by phase-delays and depressive episodes by phase-advances of the diurnal sleep-wake and activity patterns. In a way, phase-delayed people are constantly in the depressive phase of the bipolar disorder.

Treating Extreme Larks and Owls

Trying to regulate sleep-time with melatonin supplements can be tricky. If you are phase-delayed, thus producing melatonin in summer from 2am until 10am, if you take a melatonin pill at 10pm in order to go to sleep earlier, your clock will see a winter-like melatonin signal of 12 hours duration (10pm-10am) and will make you depressed within a couple of days.

The best way to shift a clock is by using bright light. Instead of buying a $500 light-box, you can, for much less money, build your own for a fraction of that money. You need a piece of board, 3-4 strong neon lightbulbs, balasts, a switch, a plug, and some wires. An hour of fun, and you have an apparatus that is just as good and effective as the hifallutin corporate gizmo. Use the light box at appropriate times (dawn for owls, dusk for larks). If you are an extreme owl, when you first get up in the morning, immediately go out in the sunlight (that is thousands of lux of light energy, compared to hundreds from a lightbox) for a jog with your dog. If you do not have a dog, buy one – that will force you to go for a walk early in the morning. Well-scheduled meals also help.

Do not take anti-depressants. They tend to not work for circadian-based depression and may just mask the symptoms (i.e., you “feel” good while your body is falling apart). Do not use melatonin supplements. Do not use alcohol – it may make you fall asleep fast, but the sleep will be shallow and erratic and you will wake up feeling lousy instead of rested. Caffeinated drinks are fine, except during the last 2-3 hours before your intended bedtime, at which time a warm glass of milk may be better.

Make a routine in the evening. The last 2-3 hours before bedtime stay out of the bedroom (bedroom is only for sleep and sex), and switch off all the screens: no TV, no computer, no gameboy. Reading a book while sitting in an armchair in the living room is fine. Just sitting on the porch and thinking will help you wind down. As the evening progresses gradually turn down the lights. Once the bedtime arrives, go to the bedroom, go to bed, switch off the light (pitch darkness) and go to sleep if you can. If you cannot, get up for a few minutes, but keep your lights dim, still no screens, no caffein, no food.

Of course, all of the above are the strategies to shift your clock to a “socially accepted” phase. But you are not crazy or sick. It is the societal pressure to get up at a certain time that is making you sick. Try to get a job that fits your natural schedule. Work at night, sleep during the day (in a pitch-dark, light-tight, sound-proof room) and enjoy life in all its quirkiness.

If you need to go to the bathroom in the evening or during the night, do not turn on the light. Can’t you find your vital organs in the dark? If neccessary, a very dim nightlight (or indirect light from the hall) is OK. If you wake up in the middle of the night, do not get up or switch on the light. Have sex instead. Hopefully your partner will enjoy being woken up by your kinky activities. You will both crash into pleasant deep sleep afterwards. If you do not have a partner, just do it yourself without switching on the lights (as I said, you can find your vital organs in the dark). Jocelyn Elders was onto something….

Why We Sleep Like This?
A classical sociobiological just-so story posits that this kind of individual variation on the lark/owl continuum had an adaptive function, namely to ensure that at every time of night at least one member of the tribe was awake. Thus some stood guard early in the night, others late in the night, listening to the sounds of the jungle (or savannah, or whatever) while the midnight break is thought to have been used for copulating with whomever also happens to be awake at the time – this was before the social invention of sexual monogamy.

Why did cave-men live in caves? Caves are rare and expensive pieces of real estate. If you find one, it is likely to be already inhabited, thus you need to kick out the old tenants (bears?) in order to move in. Then you have to defend it from others who also want this nice piece of property. And it is difficult to defend a cave – it has one entrance – the rest is a trap. If the intruder is really dangerous you have two options: to go out and be killed outside, or remain inside and get killed in the cave. What is so important about the cave that warrants such a risk? Is it that a possible attack can come only from one side, thus requiring only one guard at a time? Is it that newly naked human animals needed shelter from bad weather that they did not need while they were still furry? Is it to protect the newly acquired fire from being extinguished by rain? Does it make easier the task of keeping the herd of not-yet-that-well domesticated animals all together and preventing it from running away? Possibly all of it – we’ll never know – it’s a “just-so” story. But do not forget one very important property of the cave: it is dark inside. It is easy to sleep in the dark. Most animals find shelter or burrow when they want to sleep – this is not just to hide from the enemies and weather, but also to hide from the sunlight.

Sleep is one of the strongest human needs. If you have read the last part of my four-part series featured on the previous Tangled Bank, you have read my ideas why we still don’t know what sleep is for (though see the current state of knowledge in, e.g., this paper: Origin and evolution of sleep: roles of vision and endothermy (pdf)). While I am not advocating ditching modernity, cutting off electricity and going back to the old sleep pattern, we still do not know enough about sleep in order to make the 24-hour society work for us without too much in the way of health consequences.

Hey, teacher, leave us kids alone (to sleep late)

It has been known for a while that adolescents are quite extreme “owls” no matter what their chronotype may be earlier and later in life (and fortunately, school districts are starting to recognize this). This has been attributed to the surge of sex hormones in early adolescence. Responsiveness of the circadian clock to sex hormones has not been studied much (virtually not at all, though I should be able to publish my data within a year or so, sorry for not being able to divulge more detailed information yet), yet most people in the field believe this to be the case, even if no details are available yet.

Now a new paper suggests that the end of adolescence should be defined as a time when the circadian clock goes back to its “normal” state. But, wait a minute, the hormones do not disappear at that time. Thus, if the clock is responding to the hormones at the onset of the adolescence, does this mean that the end of adolescence should be defined as the time when the clock becomes UNRESPONSIVE to the hormones? How does that happen and how is that triggered?

Anyway, I still have to look at the study itself (this is just a press release). I want to see if females both become “owls” AND quit being “owls” earlier than males [OK, I took a peek at the paper and yes, they do]. Also, in women, hormones (mostly estrogen and progesterone) surge in monthly cycles that end abruptly at menopause, while in men testosterone (mainly) is pretty high (with a small circadian variation) continuously and only gradually declines in old age. The lifelong sex difference they found in the study is quite interesting in this light.

Also, I like the way they tried to tease away social influences from pure biology, though they are correct to warn they do not know in which direction causation flows: do the teenagers sleep late because they party, or do they party because they are wide awake…..and now a closet sociobiologist is waking up somewhere in my head trying to explain why would it be adaptive for teens to stay up late and play, including perhaps experimentation with sex while elders are asleep (squash, bad sociobiologist…go back to sleep…there, good boy)….

Wake Me When It’s Over

“Societies define adulthood in different ways, from entering puberty to entering the workforce. But circadian clock researchers now suggest that adolescence ends when we stop sleeping in.Teenagers are more likely to have trouble getting out of bed in the morning than are young children or adults–a finding many studies attribute to a chronic lack of sleep. But researchers at the University of Munich wondered if a more fundamental biological factor played a role.Using a brief questionnaire distributed in clinics, universities and online, Till Roenneberg and colleagues collected data on sleeping patterns from more than 25,000 people in Germany and Switzerland. As part of their analysis, the researchers determined each person’s “chronotype” by calculating the mid-point of their sleep–halfway between going to bed and waking up–on days when the subjects slept as late as they wanted.A surprising pattern emerged. Average chronotypes drift later and laterduring the teen years, but then begin to move steadily earlier after the age of 20, the researchers report in the 28 December issue of Current Biology. It still isn’t clear why, says Roenneberg.

Teenagers may sleep late because they’ve been out partying or they may go out because they’re wide awake at 11 pm. However, he says, the team also saw a similar pattern in teenagers in rural valleys in South Tyrol–where nightclubs are relatively scarce. There, the average chronotype wasabout an hour earlier, but the overall age pattern was the same. The researchers also saw differences between the sexes, with females having an earlier average chronotype than males until around age 50–consistent with menopause–when the correlation between age and chronotype seems to break down. This suggests, Roenneberg says, that biological factors such as hormones have an important influence on the tendency to sleep late.Sleep researcher Mary Carskadon of Brown University in Providence, Rhode Island, says that both social and biological factors are likely involved. Finding the biological trigger–if any–could lead to a better understanding of what drives circadian rhythms, she says.”

Of course, the study was done on Germans. Even in disco-less South Tyrol there is electricity and modernity. It would be cool to see a similar study performed in a culture where sleep is divided in two parts (late-night sleep and afternoon Siesta), like in Mediterranean and Latin American countries, as well as in a real primitive society in which sleep is divided into two parts (early-night sleep and late-night sleep with a break for sex around midnight).

Societal Constraints

One thing we know is that darkness is an important aspect of the environment conducive to sleep. Silence is another. And we do not need science to tell us this – it’s been known forever. I remember, as a kid, learning the “sleep manners”, along with learning how to say “please” and “thank you”, how not to interrupt adults when they were on the phone, and other early lessons of life. By “sleep manners” I mean behavior when there is someone asleep in the house: one is not to enter the room with the sleeping person, not to switch on the lights, not to switch on the noisy appliances (TV, vacuum cleaner, hair dryer or wash machine), not to talk at all if possible, or reduce it to the briefest quietest whisper if absolutely neccessary. One is to walk around on tiptoes, although the best idea is just to leave the house for a while. There was also a ban on telephone use between 10pm and 8am and again between 2pm and 5pm (so-called “house order”). Sleep was treated as something sacred. Be it at night, or the afternoon siesta, only a life-or-death emergency situation warranted waking someone up.

As Robert Anston Heinlein said:

Waking a person unnecessarily should not be considered a capital crime. For a first offense, that is.

One thing I noticed upon arriving to the States is that nobody here seems to have any notion of “sleep manners”. I have seen (and experienced) many times people barging into the room containing a sleeping person, switching on the lights and TV, talking, even talking to the sleeping person, all the while not being even aware that this is a Big No-No, very inconsiderate, and extremely rude. When confronted, the response is usually very defensive, stressing the person’s individual right to do whatever he/she wants and not bother about being considerate about some lazy bum who is sleeping at an inappropriate time. Whoa! Stop right there!

First, individual rights are assumed to mean that you can do whatever you want as long as that does not hurt another person in some way. Waking someone up is harassment – of course it hurts someone. Second, there is no such thing as inappropriate time. If you can, you sleep whenever you can. There is no appropriate or inappropriate time. What do you do if someone is working the night-shift (like my wife often does, and I sometimes do, too)? That person will sleep during the day, so you better shut up. Third, what is this about sleeping being a sign of laziness. The “owls” are constantly being treated as lazy, though they are more likely to be sleep-deprived (cannot fall asleep until the wee hours, then being rudely awoken by the alarm clock after just a couple of hours) and spend more hours awake (and presumably productive) than “larks” do. If you are asleep, this means you need it. If you are rested enough you cannot physically remain asleep or go back to sleep again. You are wide awake. Thus, when you see someone asleep, it is because that person needs sleep right there and then. Sleep is not laziness. Laziness is “lots of front-porch picking”.

Pretending that sleep-need does not exist is also institutionalized. I am not talking just about night-shifts and rotating shifts (those will kill you), night flights, being available for communication 24/7, stores open 24/7, etc – those are part of a modern society, will not go away, and we just need to learn how to adjust. I am talking about the building standards. With a huge proportion of the population working at night, why do windows have no blinds? Some old manors do, but new buildings do not. Never. Some have fake blinds, just for show, screwed into the outside walls on the sides of windows, yet cannot be closed. There are no built-in black curtains, or roll-down wooden blinds. It is difficult to find such curtains in stores if one wants to install one. What is going on? I have never seen, heard, read about, or experienced another country in the world in which sleep is not sacred, and blinds are not an essential part of a house.

I see some striking parallels between the way this society treats sleep and the way it treats sex. Both are sinful activities, associated with one of the Seven Deadly Sins (Sloth and Lust). Both are associated with the most powerful biological needs. Both are supposed to be a taboo topic. Both are supposed to be done in private, at night, with a pretense that it is never actually happening. Education in sleep hygiene and sex hygiene are both slighted, one way or another (the former passively, the latter actively opposed). Both are thought to interfere with one’s productivity – ah, the good old Protestant work ethic! Why are Avarice and Greed not treated the same way? Raking in money by selling mega-burgers is just fine, and a decent topic of conversation, even a point of pride. Why are we still allowing Puritan Calvinist way of thinking, coupled with capitalist creed, to still guide the way we live our lives, or even think about life. Sleeping, whether with someone or alone, is a basic human need, thus a basic human right. Neither really detracts from the workplace productivity – au contraire: well rested and well satisfied people are happy, energetic, enthusiastic and productive. It is sleep repressed people, along with the dour sex repressed people, who are the problem, making everyone nervous. How much longer are we going to hide under the covers?

Perhaps not that long. It appears that we are slowly waking up to sleep problems (pun intended). More and more companies are allowing naps, and even providing nap-rooms. More and more school districts are moving high-school morning schedules later, as during teenage years, under effects of sex hormones, the circadian clocks are all temporarily “owlish”. Adolescents are not crazy and lazy – they physically cannot fall asleep at a normal bed time, and physically cannot awake and feel rested early in the morning (elementary and middle school kids can, as their hormones have not surged yet).

It seems political advisors have caught on, too. During the presidential debates I blogged about the likely tacks used by the handlers to get their candidates to be at their peak performance levels in early evening – something apparently more difficult for Bush than Kerry ( see this and this). Battle for More Free Time, including its subset: the Battle for Sleep, is re-entering the political domain again. Check the links to the websites commenting on this newly-brewing movement. And of course, the art of matchmaking is starting to include the lark/owl questionnaire, assuming that people of the same chronotype are a perfect match (I saw this in a magazine in a waiting room, but if anyone knows if online dating services are doing this, please let me know).

Popping melatonin pills is one of the latest crazes. Melatonin failed as a sleeping pill and its uses as a scavenger of free radicals are dubious at best. It can shift one’s clock, though. However, it cannot help against jet-lag or effects of shift-work (shift-lag) as melatonin is likely to shift only the main brain pacemaker in the suprachiasmatic nuclei. The problem with jet-lag and shift-lag is dissociation of rhythms between cells in different tissues, i.e., your brain clock may resynchornize to the new time-zone/schedule in a couple of days, the clocks in your heart and lungs in a week, and in your stomach and liver in a month. In the meantime, everything in your body is desynchronized and you feel really bad. If you keep changing your work shift over and over again, you never get to achieve complete synchronization, leading to long-term effects on health, including significant rise in heart attacks, stomach ulcers, and breast cancer.

Well, intercontinental flight is here to stay, and some shift-work is neccessary for the modern society to survive. It is now understood that some people (chronotypes) adjust to night-shifts and even properly executed (non-rapid, phase-delaying) rotating shifts, better than others. People have always tried to self-select for various schedules, yet it has recently started to enter the corporate consciousness that forcing employees into unwanted shifts has negative effects on productivity and safety, thus bottom line. See Chernobyl, Bhopal, Exxon Valdese and Three Mile Island accidents – all caused by sober but sleepy people at about 3am, just like thousands of traffic accidents every year.

So how does the future look like? As usual, don’t ask scientists, especially members of the Academy. If you want answers to scientific questions about the future, you have to read science-fiction – this is a sacred duty of all scientists. Cory Doctorow who blogs on the group blog Boing Boing, has written a novel “Eastern Standard Tribe” (you can buy it, or download for free here) that answers just such questions. In the future not so far, people form communities not according to geography, or hobbies, or ideology, but their time zone. Everyone, no matter where on the planet, awake and at the computer at the same time, belongs to a particular Time Zone Tribe. Thus an owl from one country, an average from another and a lark from another will all be typing and reading at the same time, thus will meet in cyberspace and forge alliances against other time-zone communities. Inter-time-zone wars ensue, intrigue and treason happen, boy meets girl…the story is wonderful and will make you think about sleep, and about circadian rhythms, about Internet, and about being human, all in ways you never thought before. Enjoy.

City Of Light: Insomniac Urban Animals

The Cities are the topic of the month here at Scientific American (and at least this week on the blogs), so I should chime in on an aspect of urban ecology that I am comfortable discussing – the effects of increased light at night on animals.

Not all species of animals are negatively affected by the urban environments. Even humans are not driven to insanity by the urban jungle. Some species are really thriving – rats, mice, squirrels, bats, alligators in sewers, sparrows, pigeons, starlings, crows, house flies, mosquitoes and cockroaches come to mind. Many birds have evolved (or invented) quite nifty adaptations to urban life. Of course, animals we domesticated and keep as pets, like cats and dogs, don’t really care about the city vs. country, as long as they are with us and we take good care of them.

But there are definitely negative effects as well. After all, just counts and surveys of species make it obvious that many species are not thriving in dense urban ecosystems. Not all cities are the same either. A large, dense city is likely to be much less hospitable to many species than urban sprawl where much greenery and the original natural habitat are still preserved between the cul-de-sacs. Just watch the wilderness appearing on my back porch: skinks, tree frogs, Luna moths, white-tailed deer, rabbits, opossums, racoons, cicadas, endless species of birds…and I am in the middle of the Triangle, NC.

Large animals, in general, will not do well in cities, and not just because direct encounters with humans can often be deadly (imagine what would happen to a herd of bison if it tried to trek through streets of Manhattan?). Herbivores will be starved due to lack of plants, and carnivores will starve due to lack of herbivores. Thus many ecological factors affect the ability of species to adapt to the City – food, predators, shelter, and, importantly, noise.

But I will focus only on light today. Light pollution is often discussed in the context of impossibility to see the wonderful starry night, but effect of night light on wildlife is a problem beyond human esthetics – it has real-world consequences for the health of ecosystems. And the effect of light almost always involves, in some way, the circadian clock.

Circadian clock – a very, very quick primer

There is quite a lot of biological complexity in the circadian clock, but let’s just remember the few key, basic points.

Circadian clock is a structure (in animals it is in the brain) that governs the daily rhythms of biochemistry, physiology and behavior.

All organisms living on or near the surface of the Earth have a circadian clock. Those that now live deep down inside the soil or rocks or caves, or on the bottom of the ocean, may have secondarily lost the clock that their ancestors once had [1,2].

Having a circadian clock is an adaptation to the cycles of day and night in the environment. Where such cycles are altered, e.g., near the poles, the animals have evolved the ability to turn their daily clocks on or off as appropriate.

Circadian clock keeps ticking in constant darkness, or constant dim light. But in many species, constant intense light disrupts the rhythm.

The clock is reset (entrained, synchronized) each day by the alternation of light and darkness. Species differ as to the intensity of light needed for this resetting to take place. While physiological laboratory experiments usually test the light intensity against the background of complete darkness (in which the sensory systems can get adapted to the dark and become more sensitive to light), it is the difference in light intensity between day and night that is of ecological relevance.

Clock is not a dictator

As much as the circadian clock is “hard-wired” in the brain and determined by the clock-work of genes turning each other on and off, there is still quite a lot of plasticity of behavior – animals can act against the signals from the clock and do stuff at odd times if needed.

For example, when hungry, nocturnal animals will hunt during the day, e.g., man-eating lions hunting at dusk and early night on moon-less night, have to hunt during the day when the moon is full.

Also, these days bats in Austin, TX are flying out earlier at dusk due to prolonged dry weather conditions decimating their food.

Two species of golden spiny mice in Israel live in the same spot – one of them is more aggressive, so the other one has evolved adaptations (including even changes in the eyes) to forage during the day instead of night. Yet, when placed in isolation in the lab, both species are strictly nocturnal, active only at night, which shows that day-time foraging goes against the clock, i.e., is not the adaptation of the clock itself [3].

Finally, when population of rats in a city gets too big, some individuals are displaced. They are displaced in space – foraging on the surface instead of underground – and they are displaced in time – foraging during the day instead of during the night. If you see a rat digging through the garbage bags on the street in the middle of the day, you know that the total population of rats under ground is absolutely enormous! If you are interested in learning more about the fascinating ecology of urban rats, read the wonderful book ‘Rats‘ by Robert Sullivan.

Light at night, clocks and the outside world – behavior

One of the adaptive functions of having a clock is to synchronize one’s activities to that of other players in the ecosystem [4]. You want to go out hunting at the time when your prey is out and about and easy to catch. You want to hide (and sleep) while your predators and enemies are out on the prowl.

But what happens when the difference in the intensity of light is not very different between day and night, as in well illuminated cities? Some species will remain nicely entrained to the cycle, but others will not. Some individuals will be better entrained than others. Some will have their clocks reset over and over again and they will behave at different odd times each day, while in others all rhythms will get lost and they will be out and about all the time.

Thus, many individuals will be going about their lives at inappropriate times, perhaps when the predators are around (and predators are doing the same – one or another will be hunting at any time of day or night), or when the prey is hiding (so too much energy is wasted in looking for elusive food). As a result, many individuals will starve, or get eaten, or miss reproductive opportunities (hey, where are all the potential mates – why are they all hiding and sleeping at the time I am looking for them everywhere?).

Living in an environment in which is is hard to tell if it is day or night is similar to living without having a circadian clock at all. A couple of studies out in the field [5,6,7], with a couple of different species of rodents in which the clocks have been surgically removed from their brains, showed that such animals wonder around at unusual times and are significantly more prone to predation (this is a scientific way of saying: “they got slaughtered by wild cats within hours”).

Light at night, clock and the inside world – physiology

Another adaptive function of the clock is to synchronize events happening inside the bodies, both with each other and with the outside environment. It saves energy if two compatible functions in the body happen simultaneously, while incompatible events are happening at different times. By tuning into the outside cycles of light and dark, the body allocates different biochemical and physiological functions to different times of day, thus saving energy for the animal overall.

And energy is the key. At the time when food is around, it pays to invest energy in finding it. At times when food is hard to find, it is a good idea to use less energy, to stop, hide and sleep. The rate of energy production and use by the body – the metabolism – can be measured in warm-blooded animals (the ‘euthermic’ animals like birds and mammals) by measuring their core body temperature. Higher the metabolism, higher the temperature.

Normally, body temperature cycles throughout the day. Circadian clock drives this cycle so, for example, our bodies are coldest at dawn, and warmest in late afternoon. In birds the difference between the low and high point during the day is routinely a whole degree Celsius. And some small birds, like swifts and hummingbirds, let their temperature drop much, much more during the night (this is called “daily torpor”).

Having or not having food affects how much the body temperature will drop during the night. A hungry animal will save energy by dropping body temperature at night much more than a satiated animal [8]. Yet, temperature will rise to its normal levels the next day in order to give the animal sufficient energy (and speed of reaction) to successfully forage again.

Body temperature drops at night when there is no food, and it also drops during the day if there is no light-dark difference - Ref.8


Light affects this: if there is no difference in light intensity between day and night, e.g., in the laboratory in constant darkness, both daytime and nighttime temperatures will fall in hungry animals [8] – they would become too slow and feeble to forage effectively if out in the field. But constant light has the opposite effect – keeping the body temperature artificially high at all times, i.e., not allowing the hungry animal to save energy by dropping its body temperature. The energy balance, especially in a small animal, can quickly become negative, leading to death of starvation.

Reduced perception of day-night changes in light reduces the amount of change and slows down the change in body temperature (top - normal vision, middle - eyeless, bottom - obstructed vision) - Ref.9


Light at night, clock and reproduction

In many birds, length of day affects egg-laying in a way that helps the animal determine the total size of the clutch of eggs: how many she lays in one breeding attempt (usually one per year). Data from the laboratory (in chicken, quail and turkeys) [9,10] and from the field (bluebirds [11], also swallows and owls – unpublished data) suggests that this is a widespread mechanism in a variety of bird species.

In early spring, a bird may lay a lot of eggs in a clutch - Ref.10

In late summer, the bird may lay a smaller clutch - Ref.10

If the difference between light intensities at day and night is too small for the bird’s brain to integrate, the bird may be making too much of a breeding effort – laying too many eggs over a period of too many days, perhaps even throughout the year, thus exhausting her internal energy resources, while bringing too many hatchlings to life while unable to feed them all…a disaster all around.

Light at night, clock and calendar

There is a reason for the season. Many organisms do certain things at particular times of the year; breeding, molting, migration and more. The internal “calendar” they use to time such changes in behavior is dependent on the circadian clock which measures the gradually changing length of day throughout the year. The precision of such a measurement can be quite astonishing (see swallows of San Capistrano) [12].

So, what happens if there is not much of a difference between daytime and nighttime illumination? The clock interprets this as constant light, which is the ultimate “long day”, so the animal will constantly be in the “summer mode”, e.g.,. constantly breeding, or constantly trying to migrate or constantly molting its feathers or hair. All of this is energetically costly, and thus maladaptive, and will lead to exhaustion and eventual death of the animal (that is on top of not being in synchrony with other individuals of its species, see above).

Light at night, clock and orientation

When a moth wakes up in the evening and starts flying to find food, it orients by the Moon. It assumes a constant angle to the Moon and keeping that angle allows it to fly in a straight line. After all, the Moon is high and very far away, so flying along does not change the Moon’s relative position in the sky. This is called “transverse” or “Y-axis” orientation.

But the Moon moves across the sky during the night. If a moth is flying for a longer time, it will use its internal clock to compensate for this movement by gradually changing the angle.

What if, instead of the Moon, the moth sees another bright light, perhaps the one on your porch? It starts using it for orientation. At first, it will fly in the straight line. But as it comes closer to the light, the angle changes – the light “moves” in relation to the moth. So the moth compensates by turning in order to keep the constant angle. And then it turns again, and again, and again, spiraling in until it hits the light itself. By that time the light is so close and so bright it looks more like the Sun than the Moon. Its clock gets reset to “day”. So the nocturnal moth alights nearby and, instead of foraging for food, falls asleep. In a wrong place, where it is an easy pick for predators – bats at night, birds at dawn [13,14,15,16].

Birds also orient by celestial bodies. During the day, they orient by the Sun. Again, they use their internal clocks to compensate for the Sun’s movement across the sky. At night, they may use the Moon for orienting, but they certainly use the stars [17]. All the artificial lights become stars. Birds get disoriented, fly in all the wrong directions, and hit the windows and die.

What to do?

This post is really NOT about the solutions, but rather about the underlying science of light effects on animal behavior, physiology and health. I will leave the solutions to others who are experts on engineering or urban policy, who may use the science described above to get informed as to what kinds of solutions may work best.

From what I know, many cities are now starting to tackle the problem of light pollution. Sky lights are banned in some places or at some times of the year (e.g., times of big bird migrations). Many tall corporate buildings now instruct their tenants to turn off the lights at night. There are new designs of street lights that point down – the street below is illuminated even better, much much less light (and diffused, not pointed) goes up to the sky wasting energy and confusing the critters flying by. I am sure there are other things that people do, or things that can be done to reduce the amount of light, or at least the appearance of light sources as “points”, that can be adopted by cities worldwide.

We will never make the cities completely dark at night. And that is OK. After all, the Moon and the stars make nights quite bright out in the wilderness as well. All we need is to make sure that the difference in light intensity between day and night is sufficient for animals to entrain their clocks properly to the daily cycle of bright-light and not-as-bright-light, and they should be fine.


[1] Lee, D.S. (1969). Possible circadian rhythm in the cave salamander Haideotriton wallacei. Bull.Maryland Herp.Soc. 5:85-88.

[2] Trajano, E. and Menna-Barreto, L. (2000). Locomotor activity rhythms in cave catfishes, genus Taunayia, from Eastern Brazil (Teleostei: Siluriformes: Heptapterinae). Biol.Rhythm Res. 31:469-480.

[3] Kronfeld-Schor, N., Dayan, T., Elvert, R., Haim, A., Zisapel, N. and Heldmaier, G. (2001). On the use of time axis for ecological separation: Diel rhythms as an evolutionary constraint. Amer.Nat.158:451-457.

[4] Fleury, F., Allemand, R., Vavre, F., Fouillet, P. and Bouletrau, M. (2000). Adaptive significance of a circadian clock: temporal segregation of activities reduces intrinsic competitive inferiority in Drosophila parasitoids. Proc.R.Soc.Lond.B 267:1005-1010.

[5] DeCoursey, P.J., Krulas, J.R., Mele, G. and Holley, D.C. (1997). Circadian performance of Suprachiasmatic nuclei (SCN)-lesioned antelope ground squirrels in a desert enclosure. Physiol.&Behav. 62:1099-1108.

[6] DeCoursey, P.J. and Krulas J.R. (1998). Behavior of SCN-lesioned chipmunks in natural habitat: a pilot study. J.Biol.Rhythms 13:229-244.

[7] DeCoursey, P.J., Walker, J.K. and Smith, S.A. (2000). A circadian pacemaker in free-living chipmunks: essential for survival? J.Comp.Physiol.A 186:169-180.

[8] Herbert Underwood, Christopher T. Steele and Bora Zivkovic, Effects of Fasting on the Circadian Body Temperature Rhythm of Japanese Quail, Physiology & Behavior, Vol. 66, No. 1, pp. 137-143, 1999

[9] Zivkovic BD, Underwood H, Siopes T., Circadian ovulatory rhythms in Japanese quail: role of ocular and extraocular pacemakers, J Biol Rhythms. 2000 Apr;15(2):172-83.

[10] Zivkovic, B.D., C.T.Steele, H.Underwood and T.Siopes. Critical Photoperiod and Reproduction in Female Japanese Quail: Role of Eyes and Pineal. American Zoologist 2000, 40(6):1273 (abstract).

[11] Caren B. Cooper, Margaret A. Voss, and Bora Zivkovic, Extended Laying Interval of Ultimate Eggs of the Eastern Bluebird, The Condor Nov 2009: Vol. 111, Issue 4, pg(s) 752-755 doi: 10.1525/cond.2009.090061

[12] BD Zivkovic, H Underwood, CT Steele, K Edmonds, Formal Properties of the Circadian and Photoperiodic Systems of Japanese Quail: Phase Response Curve and Effects of T-Cycles, Journal of Biological Rhythms, Vol. 14, No. 5, 378-390 (1999)

[13] Kenneth D. Frank, Impact of Outdoor Lighting on Moths: An Assessment, Journal of the Lepidopterists’ Society 42 (no. 2, 1988): 63-93.

[14] Sotthibandhu, S. & Baker, R.R. (1979). Celestial orientation by the Large Yellow Underwing Moth, Noctua pronuba L. Anim. Behav., 27, 786-800.

[15] Baker, R.R. (1979). Celestial and light trap orientation of moths. Antenna, 3, 44-45.

[16] Baker, R.R. & Sadovy, Y.J. (1978). The distance and nature of the light-trap response of moths. Nature, Lond., 276, 818-821.

[17] Sauer, E.G.F. and E.M.Sauer, 1960. Star Navigation of Nocturnal Migrating Birds. In Cold Spring Harbor Symposia on Quantitative Biology, Vol. 25. pp.463-473.

Images: U.S. light pollution map: NOAA; San Francisco at night, by Thomas Hawk on Flickr (part of the Ligh pollution Flickr collection); Moth attracted by porchlight from Wikimedia Commons. The rest of the images are drawn by me, including from my papers (the original raw files, not copied from final PDFs).

Books: Michael Pollan – The Omnivore’s Dilemma

I originally reviewed this book in December 2006. Shows how my thinking and writing have evolved over the years 😉


I have read the book a couple of months ago and never found time to write a review till now. I also remember that I finished the book on a Thursday afternoon – an important piece of information as it is on Thursday afternoons that there is a Farmers’ Market here in Southern Village, barely a block from me. The first thing I did when I closed the book was to walk up to the Farmers’ Market, buy some locally grown food and talk to the farmers about all the issues raised in the book and, lo and behold, they all agree with Pollan on everything I asked them about.

They were also a little taken aback that I tried to talk to them. But, I grew up in the Balkans. A big part of going to the Farmer’s Market is to chat with the farmers, banter, joke, complain about the government, haggle over prices, and make sure a kilo of cheese is reserved for you for next week – it is a very friendly and talkative affair. Great fun! Here, there is much more of a class divide. The farmers set the prices. The elegantly dressed city-slickers pick and pay. And all of that is done pretty silently, with a minimal exchange of words. No eye-contact. Nobody is haggling! At the Farmers’ Market nobody is haggling!?*@#%$^&! Travesty and Heresy!

In his book, Michael Pollan initially set out to make three – industrial, organic and personal – types of meals, but once he learned more, he realized he had to do four: industrial, industrial-organic, local-sustainable, and personal.

So, although the book officially has three parts, it really has four. Each of the four parts also reads differently and has a different style and tone:

The first part (industrial) is full of facts, stats, governmental documents, etc. – it reads like Molly Ivins’ Bushwacked or Chris Mooney’s Republican War On Science, although I heard he played loose with some stuff, i.e., cited as true some studies that are very contentious within the scientific community.

While I am a biologist, focusing on animals made me “plant blind” and I learned more about biology of corn from this book than I ever knew before.

The key event, according to Pollan, is the change, during Nixon administration, in the way farmers are paid for corn – everything else flows from that single event: the monoculture, the oil, the feedlots, the fertilizers and pesticides, environmental destruction, obesity and McDonalds.

The second part (industrial organic) is a little bit less of an onslaught of information and he gets a little looser and slower, a bit more personal. He looks at the way organic food production changed since the 1960s hippy farms to today’s giant organic producers who are, more and more, playing by the rules of Big Agra.

While the food they produce is still better than the Industrial and the practices are still more energy and environmentally friendly than Industrial, it only looks good because it is compared to the Big Industrial which is totally atrocious. This part of the book resulted in a big back-and-forth debate between Pollan and John Mackey, the CEO of Whole Foods, resulting in some changes in the way Whole Foods operates. You can find the relevant links on Pollan’s website.

The third part (local-sustainable) is totally fascinating – it is a mix of a travellogue and analysis – he keeps jumping back and forth between his dialogues with his host – Joel Salatin of the Polyface Farms – and the data. This is really the most riveting part of the book and the key element of it. This is also a part of the book that covers most new ground, not stuff found in Fast Food Nation or other well-known books. It also exposes, even better than the first part, the perniciousness of the way our agricultural system is set up, the way Big Agribusiness controls legislation and regulation, and eliminates small farmers from the competition.

Joel Salatin is a Virginia farmer who has perfected amazing agricultural practices on his farm – practically nothing has to be bought by the farm and nothing gets thrown away. Everything has its use and re-use. Everything makes sense when patiently explained to the reader. I actually bought Salatin’s book Holy Cows and Hog Heaven and read it immediately after Pollan’s.

Interestingly, although the guy is a conservative, libertarian, Christian Creationist, I agree with him on almost everything. His distrust of the Government is perhaps a little bit over the top for my taste, but his Creationism is fascinating because his whole philosophy and his whole methodology of the way he runs the farm reveals a deep understanding of evolution and ecology. His farming practice is BASED on evolutionary thinking. He is, for all practical purposes, an evolutionary biologist. Yet, he says he does not believe in evolution. How is that possible? Because he has no idea what he word “evolution” means. He probably has some “chimp is your uncle” cartoon notion of evolution, while at the same time not giving his own evolutionary ideas any name at all. Someone should tell him.

The fourth part (personal) of the Pollan’s book is in a completely different mood, very introspective, sometimes even mystical. One important thing that sets this part apart is that the type of food production described in it is the only one of the four that cannot in any way be affected by legislation, politics or activism – unless one completely bans hunting, gathering, catching, picking, stealing from neighbors, planting stuff in your garden, or collecting yeast from the air!

The best part of this portion of the book is his look at animal rights and his dialogue with Peter Singer. He, being such a typical city-slicker and “Birckenstock liberal” (Come on – slaughtering a chicken, and later a pig, made him sick? Has he never watched or participated in any kind of animal slaughter in his long life yet? Never spent some time on a farm? Dissected an animal in a biology class? What a woefully unnatural and alienated existence!), started out very sympathetic to the idea, but, over a dozen pages or so, dissects the underlying logic and discovers its fatal flows and exposes it in a brilliant paragraph – the best one in the book. You’ll find it and recognize it immediately once you read it – and you will read it because Omnivore’s Dilemma is one of the most important books written in the last few years, and should be a battle cry for many political activists and a source of ideas for many candidates for political office.

Offal is Good

Originally published on October 4, 2008, this post is about cultural norms about food, and how deeply ingrained they can become, leading to deeply visceral likes and dislikes of particular foods, regardless of nutritional value.


The offal refers to….

….those parts of a meat animal which are used as food but which are not skeletal muscle. The term literally means “off fall”, or the pieces which fall from a carcase when it is butchered. Originally the word applied principally to the entrails. It now covers insides including the HEART, LIVER, and LUNGS (collectively known as the pluck), all abdominal organs and extremities: TAILS, FEET, and HEAD including BRAINS and TONGUE. In the USA the expressions “organ meats” or “variety meats” are used instead.

Offal from birds is usually referred to as GIBLETS.

Another, archaic, English word for insides, especially those of deer, was “umbles”, a term which survives in the expression “to eat humble pie”, meaning to be apologetic or submissive.

Growing up in Yugoslavia, I was a very picky eater. But I absolutely loved offal. I loved liver and, although just a kid, I had developed 2-3 different recipes for preparing livers from various animals: pork, calf, veal, beef, lamb, duck, turkey and goose (I did not like chicken liver). My Mom fixes fantastic bread-battered brains which were treated as a special delicacy in our house. Yum! I loved to suck the marrow out of beef bones. I always picked hearts and gizzards from my chicken soup. When we had chicken, I would often eat necks and feet. Oxtail is fantastic. Beef tongue in tomato sauce is one of the best things to eat ever, in my mind.

Also, whenever we castrated a stallion, that was an excuse to get together for dinner – the fried horse testicles. All the best restaurants in Serbia serve ‘white kidneys’, i.e., pig testicles. I never really liked the blood sausage, but beef knees or pig tongues and ears served cold in aspic were a staple in our household.

So, when I came to the United States, I was quite surprised to see that people here generally do not eat any of that stuff. Not even liver! I was quite excited when I went to San Francisco and got to try the duck fries at Incanto.

A few months ago, when Chris put up braised Kobe-beef oxtail as a dinner special at Town Hall Grill, I had it every day that week – it was that good! – yet Chris said that it did not sell very well. And oxtail is not even offal – it is skeletal muscle, and the tenderest of all as it does not need to move a big, heavy animal around, or chew tons of bulky food – just swat an occasional fly. So, not even here in the Triangle, where there is a powerful food culture, and the locavore food scene is amazing, do people easily overcome their cultural barriers to eating meat that is not steak. And yes, this is a cultural barrier:

The type of offal used in any given culture depends on the favoured meat animal, which may in turn depend on religious dietary laws. Muslim countries use much lamb offal. The Chinese have numerous ways of dealing with organs from pigs.

Offal is a good source of protein, and some organs, notably the liver and kidneys, are very valuable nutritionally. In most parts of the world, especially the less developed countries, it is valued accordingly. In the English-speaking world, however, the pattern is different. In North America, there has been and still exists a squeamish attitude which prompted the title Unmentionable Cuisine for the book by Schwabe (1979). In Britain, where there used to be no, or anyway few, qualms about eating offal, overt consumption has declined in the last half of the 20th century, although the offal is in fact still eaten in processed foods where it is not “visible”.

Squeamish attitudes may be explained on various grounds. Heads and feet remind consumers too directly that the food is of animal origin. Ambivalence about eating certain bits of an animal”s anatomy, such as TESTICLES, is expressed through the used of euphemistic names. Some internal offal has surreal shapes and strong flavours, which are not to everyone’s taste. The meat of feet and ears is characterized by textures which are gelatinous and crunchy at the same time, a combination which is generally disliked in the western world, although appreciated in the Orient.

Another dimension in the USA is historical – for a very long time, whenever an animal at a farm was slaughtered, the owners got the steaks, and the slaves got the offal. Thus, there is a racial differentiation here as well – the whites do not have a tradition of cooking offal and tend not to have family recipes and cookbooks about it, while the blacks do have such a tradition and the recipes come down through generations, from mothers to daughters. I have noticed especially here down South, that the country-club-whites especially look down their noses with disdain at offal dishes and their almost visceral disgust with them has more than a little of a classist and racist tinge to it.

Which is unfortunate. There are many places on this planet in which there is not much money going around, and the environment is not too conducive for raising sufficient amounts of grains, fruits and vegetables to feed everyone. Thus, many (probably most) cultures in the world have to be predominantly meat-eating. And growing animals for food is also not very easy or cheap either. So, it makes sense – economic sense if nothing else – to use every last edible bit of an animal. That way, each animal provides more meals to more people than if just steaks were to be eaten. This, in turn, means that fewer animals need to be grown and slaughtered.

In such places – and I have seen that in rural Serbia myself growing up – there is an almost spiritual connection to the farm animals – the slaughter is not something done lightly. It usually involves the entire large family (and friends and neighbors), the slaughter is performed with utmost care, almost ritually. And the greatest care is made not to let any piece go to waste.

At the time when the food business is straining the economy in the USA, ruining the farmers, endangering the people eating meat, done in a way very nasty to the animals, and using far too much energy (aka Oil), a little efficiency may help, including a change in culture in ways that allow us to better utilize each individual food animal (see this, this, this, this, this, this, this, this, this, this, this and this for background and additional information about the economics and politics of food).

It is not a surprise to me that the first cookbook ever to focus on just one type of offal – the testicles – was written by a Serbian chef – The Testicles Cookbook – Cooking with Balls by Ljubomir Erovic:

The Testicles Cookbook – Cooking with Balls is a multimedia cookbook complete with how-to videos on cooking testicle dishes. Including Testicle Pizza, Testicle Goulash and White Wine Testicles, this is a short teaser taken from the full cookbook, written by Serbian testicles chef, Ljubomir Erovic. The full book is available to buy on YUDU in English and Serbian.

Guardian: Cooking with balls: the world’s first testicle cookbook

Everyone’s very excited about a new e-cookbook launched today, by online publishers YUDU. It’s been compiled by a Serbian fellow called Ljubomir Erovic who has apparently been a testicular cook for some 20 years.
“The tastiest testicles in my opinion probably come from bulls, stallions or ostriches, although other people have their own favourites,” says Mr Erovic. He also uses those from pigs and turkeys in his cooking and points out that “all testicles can be eaten – except human, of course”. Glad to hear it Ljubomir.
While the ingredient is fairly challenging, most of the dishes in the book are less adventurous, from testicle pizza, goulash, battered testicles to barbecued testicles and giblets. To be fair though, it doesn’t hurt to keep it simple, and there are a couple of more demanding recipes in there, for instance, calf testicles in wine (white or red but not sweet) and testicles with bourguignon sauce.

Daily Mail: On the ball: Introducing the world’s first testicle cookbook :

Erovic also organises the World Testicle Cooking Championship, held annually in Serbia since 2004. It draws in chefs from Australia, Bosnia-Herzegovina, Finland, Greece, Hungary, Norway and Serbia. One metric tonne of testicles are prepared.
“When not cooking or eating testicles, or helping others to do so, (Erovic) now runs a company involved in the maintenance of medical and dental equipment,” the book says.

We need to eat and we need to systematically change the way the food industry is organized, but this also means we need to ‘try some new foods’ and be more efficient and less wasteful about it. You can start by frying a testicle or two one of these days. It’s not bad at all, I can guarantee you.

Image: From Offal GoodTM Blog.

Do you love or hate Cilantro?

This post, originally published on April 25, 2009, although relatively short (for me, at least) and relatively devoid of new information, was a huge hit. It got lots of traffic, many comments, many incoming links, and the discussion spread around online social networks and lasted for quite a while. All it shows, really, is how passionate people are about their food….


If you think that political or religious debates can get nasty, you haven’t seen anything until you go online and see how much hate exists between people who love cilantro and those who hate cilantro. What horrible words they use to describe each other!!!!

Last weekend, I asked why is this and searched Twitter and FriendFeed for discussions, as well Wikipedia and Google Scholar for information about it.

First – cilantro is the US name for the plant that is called coriander in the rest of the world. In the USA, only the seed is called coriander, and the rest of the plant is cilantro.

Second – there are definitely two populations of people: one (larger) group thinks that it is the best taste ever, while the other group thinks it is awful. The latter group is not simply incapable of tasting cilantro – they can taste it in minuscule quantities hidden in food and describe it as “dirty dish-soap water taste”. People who cannot stand cilantro leaf are perfectly OK with eating the coriander seed.

So, it is something in the leaf that makes the difference.

Third – anecdotal information from scouring the Web suggests (“me and my Dad hate it…”) that the type of response to cilantro is inherited. It is also not experiental (those who hate it, hated it when they were kids, those who love it sometimes first tried it when they were already old and loved it at first try, and the response does not change with age, amount, kind of food preparation, etc).

Fourth – there is no scientific literature that I could find on the genetics of this. Is the difference at the level of the gustatory (or olfactory) receptors, or at higher-level processing centers in the brain?

Fifth – there is one paper that shows that the type of response to cilantro taste has nothing to do with the individual being a supertaster or not.

Sixth – There are a few older papers that identified chemical compounds in the leaves of cilantro, and a few about the allergy to cilantro, but no final identification of the compound that makes the difference in taste to the two groups.

So, does anyone else know more about this? Let us know in the comments.

In the meantime, be nice to people who are not your cilantro-type – they cannot help it.

Image: Wikimedia Commons

How to Fix an Authentic Serbian* Sarma (Stuffed Cabbage)

Originally published in 2008.. Yes, the post is somewhat tongue-in-cheek. And yes, the recipe is real. But most interesting is the passion people feel about their food, how important is the authenticity (though any local, ethnic dish is likely a result of many foreign influences over the years), and especially how important it is that it tastes exactly the way Mom fixed it.


Sorry to keep you all waiting so long, as there was other work to do, but here is the method for producing the most authentic sarma. As some steps may be too difficult, I will be adding tips and tricks along the way on how to do it with materials at hand – it will still be good, but you cannot call it “authentic” any more.**

Part A – Making Sauerkraut

The key to good sarma is good Sauerkraut, i.e., the sour cabbage leaves that you will do the wrapping with. And the most important piece of the puzzle for this is:

The StoneTM

Heavy, compact, dense, smooth block of rock.*** Taking one from the side of a pavement or out of a cobblestone street will do fine (but is damage to public property). But it you want the true bragging rights, then you will try, without getting caught, to steal one of the stones from a large (but slowly diminishing, for this very reason) pile of old stones, put there at least a century ago, probably longer, in a little park accross the street from the Parliament (Yugoslav, now Serbian) building in Belgrade. That stone will be perfect in every way – size, shape, density, everything, or so the legend says 😉

If you manage to pass it by customs and take it home, you are ready to begin the process of making the sour cabbage, and about a month later, the delicious sarma.

Once you have obtained a decent specimen of stone, the rest is easy. Next, buy (or have built for you) a barrel. An oak-barrel is the best. Other wood will be fine. And even plastic will do if everything else fails.

Now you have all the equipment and are ready to start.

Next: farmers market. You need to find good cabbage. The stuff in grocery stores is no good, either too pale, or purple, or frilly. You are looking for the old-style cabbage (you may have to ask your farmer friend to grow some for you, if neccessary, or grow it yourself if you have a small piece of land) – rich green, with the very tips of leaves turning slightly red or even brownish. That is the right kind. Get 20kg or so (40lbs+).

Each head of cabbage needs to be washed. If there are some leaves that are starting to rot at the tips or edges, remove them. You know how cabbage has a “core” in the middle? Use a very sharp, pointed knife to cut the core out. The cores are best eaten raw – they are delicious and taste just like kholrabi. The cabbage head will now have a square (actually, pyramid-shaped) hole in it where the core used to be. Put some salt in that hole – you may even want to rub salt into the cabbage from the inside this way.

Put the barrel in a shady place where you can keep the temperature reasonably constant – around room temperature. Thus, people usually use cellars in winter, as summer heat is bound to spoil the cabbage.

Fill the barrel with the cabbage heads. Start pouring in water, also at room temperature. While the water is pouring in, also add: about 1kg (2lbs) of salt – actually what is left after some of it was used to fill each individual head of cabbage. Also add several pieces of fresh, cleaned horseradish, and a whole cleaned and peeled red beet.

If you decided to go with a much smaller barrel for smaller quantity, or if you are using a plastic barrel, it is not a bad idea to also place a couple of large pieces of bread on top of it all. It is a matter of pride NOT to use any chemical preservatives, although the climate where you live, or the microcilmate of your cellar. may force your hand on it. You will gain experience if you do this several years in a row and will adjust all the parameters to fit yoru local conditions.

When the barrel is full of water, put the lid on. The important thing is that the lid has a diameter slightly smaller than the opening on the top of the barrel. Thus, the wooden lid actually floats on top of the water. This is why it needs to be clean.

This is also why you need The StoneTM. Wash the stone thoroughly and place it on top of the lid. The lid will, thus, push down on the cabbage and prevent any contact between cabbage and air – the most important factor in the entire process. This is also why it has to be a solid stone. Wood, plastic and rubber will not press it well enough. Brick, concrete and wood are too porous and thus full of gunk that is impossible to clean – gunk that will make your cabbage rot. Metal will react with the salt and acid or rust, and plastic may leach cancerogenic compounds – both are to be kept away from your primordial sauerkraut. The StoneTM rocks!

The process of souring lasts about a month. You have to, about once per week, replace the water in the barrel. Just open the valve on the bottom of the barrel and let it drain, then add fresh water and place the lid (and You-Know-What on top of the lid) back on. You may need to try the water and/or a little piece of cabbage to see when it is done.

Once it is done, and you keep replacing water regularly, you can just keep the cabagge in the barrel for a couple of more months, if I remember correctly, until it is all gone, or until the weather gets too hot.

Tip: if you have a small barrel and no valve on the bottom, you can probably get away with not replacing the water at all if instead you use a hose to blow bubbles in the water and thus mix the salt and the water thoroughly every week.

Part B – Fixing the Sarma

Now that you have sauerkraut in the barrel, you are ready to fix your sarma.

I. Cabbage: Take a nice, large head of cabbage, with big, healthy leaves. Take all the individual leaves off. Wash them thoroughly in hot water, several times if needed, i.e., if your sauerkraut is too salty or acidic. Drain the water and dry the leaves.

Each leaf has a thick central stem which needs to be carefully thinned (with a sharp knife) so that it can be folded and wrapped nicely. Using one leaf per wrap makes large wraps with a high meat:cabbage ratio (the way I like it). Alternatively, one can cut each leaf in half and use each half to make a small wrap. Just be consistent with your choice: all big or all small.

II. Meat filling: Use 1kg (2 pounds) of ground meat: beef, veal, pork, sausage or – the best – a mix of veal and pork.

Cut up an onion and put it in a skillet with some animal fat (oil will do, if you prefer). Cut up and add some smoked bacon or neck (or other smoked meat). Add salt, black pepper and ground red pepper. When the onion gets brown, add the ground meat, mix well, and fry it for about 10 minutes. At the end, add a cup of raw, white rice (in some places, for additional touch of authenticity, they add barley or oats instead of rice, but I don’t like this as rice remains somewhat firmer with prolonged cooking).

III. Wrapping: Take a large plate and put a single cabbage leaf on it. Put a tablespoon of the meat mix on the leaf, start folding/rolling the leaf at one end to cover the meat and start wrapping to the end. When you have a wrap that looks like a pillow, use thumb to tuck the loose end of the cabbage into the wrap. Repeat until all the meat is wrapped.

How do you know if you have wrapped it well? Wrap one, go outside to the top of a sloping downhill street. Throw the cabbage wrap down the hill. If, when it hits the bottom, it is still wrapped, you have done a good job. If it unravels while rolling downhill, you need to practice more.

IV. Cooking: Take a large pot and put some dry/smoked meat (e.g., ribs or neck) on the bottom. Start stacking the wraps in the pot. Stack them tightly against each other. Place the last remaining cabbage leaves on top. Put a little bit of water in – not too much as you do not want it to boil over and out of the pot.
Get it to boil on the stove. Then cover and place in the oven. Let it cook in the oven, set on Medium, around an hour at least.

Alternative, totally unauthentic method, which works miraculously if you do not have the space or time to make your own sauerkraut at home:
Make wrapped cabbage as above using fresh, sweet, raw cabbage instead of sauerkraut. Before wrapping, place the leaves in boiling water for just a minute until they are just soft enough to wrap, then drain and dry them and let cool off before wrapping.

Buy a bag of string or chopped sauerkraut at the store. Put it everywhere: inside, in-between, under and over the wraps. Cook a little longer than usual. The sweet cabbage becomes acidic in the process. One may also reduce the amount of dry/smoked meat by adding a little bit of vinegar and some tomato sauce instead.

V. Eating: Serve hot. Take the wraps out carefully so they remain intact. Sarma is probably already salty enough, but adding some fresh ground black pepper is usually nice. Serve with fresh, white peasant bread, mashed potatoes and the sauerkraut salad.

Sauerkraut salad? You already have sauerkraut in the barrel. Cut up some leaves, wash them throughly in cold water, add a little oil and ground red pepper/paprika. Add a little ‘raso’ (rah-sol), i.e., the slightly pink-ish, slightly acidic, salty water from the barrel.

A shot of slivovitz is the best thing to have just before the meal, while during the meal, a strong, home-brewed beer is probably the best match with sarma. If you prefer wine, then it should be red, earthy, non-sweet kind.

VI. The next day: Raso (the water from the barrel) is said to be good against hangover in the morning, in case you had a little bit too much slivovitz. Just drink a glass of it. Since it is a salty, somewhat acidic water, it can be used for fixing other dishes, e.g., soups.

The sarma itself gets noticeably better and tastier with each day’s re-heating (the effect I can attest to from just last week’s experience of having sarma for four nights in a row). If you expect important guests, fix sarma the day before, then re-heat it before your guests arrive.

*Sarma is a frequent dish all over the Balkans, with each region having its own variations of the recipe, each delicious in its own way. The recipe described here is largely based on my Mom’s way of doing things.
**There is, as far as I know, no scientific evidence for any of the empirical claims made in this post. Obviously, this field is wide open for future research.
***No stone was left unturned in preparation and writing of this post.

Photos: by me, first one taken at home (sarma fixed by Mrs.Coturnix), second one in Belgrade (sarma fixed by my Mom).