Don't mess with this guy

What would you do if your work was cited by people like Ann Coulter as "evidence" against the very phenomenon you had been studying for years?

Earth scientist Peter Doran, who encountered this problem in 2002 after studying how the climate is changing in Antarctica, responded by publishing a bold Op-Ed in the New York Times this summer.

Learn more about Doran and his work by reading my Q&A with him, which was recently published by Seed.

Why do guys get sleepy after sex?

For many women, the correlation between sex and snoring is one of those annoying facts of life: no matter when passionate encounters occur, men always seem to fall asleep immediately afterwards. Dave Zinczenko, the author of Men, Love and Sex: The Complete User Guide For Women, explained the phenomenon to Huffington Post writer Arianna Huffington this way: “Men go to sleep because women don’t turn into a pizza.”

I doubt I am ever going to become a pizza, and I’ll never have the foresight to order one beforehand. So in lieu of a cure, a better explanation will have to do. Women, too, often feel sleepy after sex. What is it, then, that spirals us into the land of nod? And could it actually be a good thing?

First, the obvious reasons for sex’s somnolent sway: the act frequently takes place at night, in a bed, and is, after all, physically exhausting (often more so for the man than the woman, although this certainly varies). So when sex is over, it’s natural to feel sleepy.

Secondly, research using positron emission tomography (PET) scans has shown that activity in the amygdala, the brain area that controls fear and anxiety, decreases prior to orgasm. University of Groningen doctor Gert Holstege, who led the study, told the London Times that “letting go of all fear and anxiety might be the most important thing, even necessary, to have an orgasm." Doing so, of course, tends to be relaxing and might explain the tendency to snooze.

Then there is the biochemistry of the orgasm itself. Research shows that during orgasm, we release a cocktail of brain chemicals, including norepinephrine, serotonin, oxytocin, vasopressin, nitric oxide (NO), and the hormone prolactin. The release of prolactin is linked to the feeling of sexual satisfaction, and it also mediates the “recovery time” that men are well aware of—the time a guy must wait before “giving it another go.” Studies have also shown that men deficient in prolactin have faster recovery times.

Prolactin levels are also naturally higher during sleep, suggesting a link between the two. It's possible that the hormone’s release during orgasm leads to drowsiness.

(Side note: prolactin also explains why we are sleepier after intercourse than after masturbation. For unknown reasons, intercourse orgasms release four times more prolactin than masturbatory orgasms, according to a recent study in the Journal of Biological Psychology.)

Oxytocin and vasopressin, two other chemicals released during orgasm, are also associated with sleep. Their release frequently accompanies that of melatonin, the primary hormone that regulates our body clocks. Oxytocin is also thought to reduce stress levels, which again could lead to relaxation and sleepiness.

What about the evolutionary reasons for post-sex sleepiness? This is trickier to explain, and no one really knows. Evolutionarily speaking, a man’s primary goal is to produce as many offspring as possible, and sleeping doesn’t exactly help in his quest. But perhaps since he cannot immediately run off with another woman anyway—damn that recovery time!—re-energizing himself via sleep may be the best use of his time.

And women often fall asleep with the men anyway (or use it for some key cuddling time), which could aid with conception (you know, gravity and all that). And when the two wake up naked together, they just might be ready to go again.

It’s also possible that sleepiness is just a “side effect” associated with a more evolutionarily important reason for the release of oxytocin and vasopressin. In addition to being associated with sleep, both chemicals are also intimately involved in what is called “pair bonding,” the social attachment human mates commonly share. The release of these brain chemicals during orgasm heightens feelings of bonding and trust between sexual partners, which may partially explain the link between sex and emotional attachment. This bond is favorable should the couple have a baby, as cooperative child rearing maximizes the young one’s chances for survival.

The bottom line is this: there are many potential biochemical and evolutionary reasons for post-sex sleepiness, some direct and some indirect—but no one has yet pinpointed the exact causes. One thing, however, is certain: we all better get used to it, because it doesn’t look likely to change anytime soon.

I will leave you frustrated American women with one final thought: if you are upset at the ubiquity of the post-sex snoring phenomenon in your men, remember that things could be a lot worse. A recent survey of 10,000 English men revealed that 48 percent actually fall asleep during sex.

Talk about coitus interruptus!

A version of this story was first published here on September 25, 2006.

Monkeys hate techno, too

Indeed. I just published this piece about the musical tastes of our evolutionary ancestors on Seed Magazine's website.

Food for chickens, poison for man

Just published this piece on Scienceline about arsenic in chicken feed. It has been featured on Environmental Health News and the Society of Environmental Journalists website.

Want some ice with that?

I'm lucky to live in New York, and not just because I share the streets with the likes of James Gandolfini. I have another, albeit less obvious, reason to celebrate as well.

My tap water doesn’t contain detectable arsenic.

Over the course of the last few weeks, I’ve been looking into arsenic levels in drinking water around the country, and what I’ve found is pretty scary. (I will post a much longer article next week on a related topic. Get pumped.) The Environmental Protection Agency classifies arsenic as a Class A carcinogen, known to cause bladder, lung, skin, kidney, liver, and prostate cancers. Long-term exposure to low levels of arsenic also leads to partial paralysis, blindness and diabetes.

Up until this year, the EPA’s standard for levels of arsenic in drinking water were pretty awful. The Natural Resources Defense Council (NRDC), a non-profit environmental advocacy organization, concluded in 2000 that “drinking water at the current EPA standard could easily result in a total fatal cancer risk of 1 in 100―about a 10,000 times higher cancer risk than EPA would allow for carcinogens in food.”

Thankfully, the EPA tightened its national regulations this past January, lowering acceptable arsenic levels from a maximum of 50 parts per billion (ppb) to 10ppb. But this new level still exceeds the recommendations of the Safe Drinking Water Act by a factor of 42.

The Safe Drinking Water Act was enacted 30 years ago to as the main federal law ensuring the quality of America’s drinking water. It deems that no cancer-causing element should be present in water at levels that will cause more than one person per 100,000 to develop cancer as a result. But Americans who are regularly drinking water conforming to the EPA’s current 10ppb standard are, according to my calculations, at a 42-fold higher cancer risk than this. One of every 2,400 Americans is likely to develop cancer from their drinking water. (The NRDC calculates a more worrying estimate of one in 500.)

One in 2,400 may sound like nothing, but think of it this way: If New York’s drinking water contained arsenic at the legal limit, over 3,300 New Yorkers would be diagnosed with cancer over the course of their lifetime as a direct result of the fact that they drank tap water.

I'm fortunate to live in a city where I can drink water well below the legal limit, but the EPA estimates that 12 million Americans are currently drinking water that exceeds it. Some of the most contaminated states are Texas, Nevada, Arizona, and Arkansas. And who knows about people who get their water from private wells: It’s up to well owners to test the water and ensure that it conforms to health standards (private wells don’t fall under the jurisdiction of the EPA, so legally, anything goes). Twenty percent of the population of New England, for example, drinks water from private wells.

I know what you’re thinking: Bottled water! But in addition to the fact that it’s ridiculously expensive, a study by the NRDC suggests that at least a third of all bottled water contains levels of arsenic comparable to tap water. Although the Food and Drug Administration technically regulates bottled water at the national level, water that is bottled and sold within the same state is exempt from these regulations―and this accounts for up to 70 percent of all bottled water.

For those of you who aren't lucky enough to drink Manhattan's pristine tap water: I'd urge you to check your water arsenic levels by calling your local water utility. If you own a private well, look into having it tested. The Water Systems Council is a non-profit organization designed to help private well owners keep their water safe and healthy.

Because really, no one should be drinking poison. ☼