More foods hinder rather than help sleep

A number of my apparently sleep-deprived friends and colleagues, upon learning I planned to write about foods that might help people sleep better, have told me they’re eager to see what I come up with.

I so hate to disappoint them. But it turns out science has yet to find a magical food that can send us right to slumberland.

“The bad news for people trying to talk about food and sleep is that ... generally it’s hard to find foods that help with sleep,” says Michael Grandner, a sleep researcher at the University of Pennsylvania’s Center for Sleep and Respiratory Neurobiology.

“The easier question,” Grandner says, “is what are the things to avoid?” Though you might expect caffeine to top that list, Grandner’s most recent research, published February in the journal Sleep Medicine, found otherwise. Tracking the diets and sleep habits of 459 women enrolled in the federal government’s 15-year Women’s Health Initiative, he found that fat was the main nutrient (out of dozens tracked) associated with getting less sleep. “The more fat you ate, the less you slept,” he says.

Women who ate the most fat slept for shorter times and took more naps, a sign that they didn’t get enough restful sleep at night. (He believes his findings apply to the broader population, not just older women.) If eating fat keeps you from sleeping, so does being fat.

“People who are obese sleep less and report that the sleep they get is not as good,” Grandner wrote in an e-mail. “Some of this may be due to high rates of undiagnosed sleep apnea in these people, but it seems that obesity itself is related to less sleep. This may have to do with the fact that the hormones that control our feelings of hunger and being full get disrupted when sleep is disrupted.” Of course, caffeine is among the substances (along with spicy foods) we should avoid late in the day if we want to sleep well.

“Caffeine can still have an effect on sleep 12 hours later,” Grandner said in a phone interview, “enough that it’s keeping alertness levels so high that we’re unable to shut it off.” Also on the don’t-drink list: alcohol. Although a nightcap might help you fall asleep, Christine Gerbstadt, a medical doctor, registered dietitian and spokeswoman for the American Dietary Association, says: “Alcohol does disrupt the sleep cycle. It delays the onset of and shortens REM sleep, which is the restful sleep” you need every night.

Both red and white wine contain melatonin, Gerbstadt says, but that hormone’s sleep-inducing properties are offset by the alcohol’s interference with REM sleep. Still, she says, you might benefit from eating red grapes with the skin on to get a little boost of melatonin.

So what about downing a glass of warm milk or munching on a tryptophan-filled turkey leg to help induce Z’s? Gerbstadt says some foods could theoretically work by mimicking powerful and potentially dangerous drugs such as benzodiazepine that boost the action of the brain chemical gamma-aminobutyric acid (GABA) in the central nervous system.

GABA, explains Grandner, is “the universal volume-turner-downer.” The substance enhances a person’s ability to fall asleep by reducing anxiety and other busy-brain conditions.

As it happens, milk contains a benzodiazepine-like substance, which could account for its legendary soporific effect. But, Grandner told me, “I haven’t found much (in the way of) controlled studies that found foods that had enough GABA to influence sleep.” Milk, herbal tea and other comforting remedies help “not by making you sleepy, but by making you more relaxed,” he wrote. “... When it comes to calming foods, there are a number that may have calming effects, but honestly the evidence suggests that it is mostly placebo.” As for tryptophan, a substance that promotes sleep, Gerbstadt and Grandner say turkey doesn’t contain enough to knock you out.

“The tired or sleepy feeling after a large meal probably has more to do with the amount of food consumed, especially carbohydrates, than anything in the food itself,” Grandner wrote. “The studies that demonstrated the sedating effects of tryptophan needed at least one and up to 15 grams of tryptophan to show an effect. You would need to eat over a full pound of meat — there are almost equal amounts in turkey, chicken and beef — to get just one gram of tryptophan.”

I have to admit I feel a bit disillusioned by all these busted myths. But maybe we shouldn’t count on food to solve our problems for us, anyway. Sleep on that.