Diet Detective: Does turkey really make you sleepy?

Here are the answers to several questions about tryptophan, sleep and Thanksgiving.

What is tryptophan?

Tryptophan is one of 20 essential, naturally occurring amino acids, which are the building blocks of proteins. Your body is not able to manufacture its own tryptophan; therefore, it must get it from food sources.

Does tryptophan help you sleep? And should you be eating it alone, or do other foods help it work better?

When tryptophan reaches the brain, it is converted into serotonin (a neurotransmitter that helps to stabilize mood) and melatonin (a hormone naturally produced in the body’s pineal gland — as it increases in your blood levels you become less alert), both of which are sleep-inducing substances. However, making sure you eat high-quality carbohydrates such as whole grains, fruit and vegetables are also important.

According to Kantha Shelke, a spokesperson for the Institute of Food Technologists and a principal at Corvus Blue LLC, “When consuming tryptophan-rich foods, the uptake of tryptophan may be enhanced by the consumption of carbohydrate-rich foods, which trigger the release of insulin, which helps clear the blood of other amino acids and enhances the uptake of tryptophan … and the associated sleepiness.”

And the National Sleep Foundation agrees: “Carbohydrates make tryptophan more available to the brain, which is why carbohydrate-heavy meals can make you drowsy. Proteins from the food we eat are the building blocks of tryptophan, which is why the best bedtime snack is one that contains both a carbohydrate and protein, such as cereal with milk, peanut butter on toast, or cheese and crackers.”

Is it true that some scientists say eating foods with tryptophan doesn’t actually help you sleep?

Some scientists believe that tryptophan from food sources (no matter what other foods you eat with it) doesn’t cross the blood-brain barrier. The following is from an article appearing in the Journal of Psychiatry Neuroscience that was written by Simon Young, a research psychologist at McGill University:

“Although purified tryptophan increases brain serotonin, foods containing tryptophan do not. This is because tryptophan is transported into the brain by a transport system that is active toward all the large neutral amino acids and tryptophan is the least abundant amino acid in protein.

“There is competition between the various amino acids for the transport system, so after the ingestion of a meal containing protein, the rise in the plasma level of the other large neutral amino acids will prevent the rise in plasma tryptophan from increasing brain tryptophan. The idea, common in popular culture, that a high-protein food such as turkey will raise brain tryptophan and serotonin is, unfortunately, false.”

Is 5-hydroxytryptophan (5-HTP) the same as the tryptophan in the food we eat?

Tryptophan occurs naturally in foods and is converted into 5-HTP, which is then converted into serotonin and melatonin.

What about taking a tryptophan supplement? Would that be better than getting it from food?

When 5-HTP is consumed as a supplement its efficacy differs from one person to another, depending on the individual’s metabolic condition. People take 5-HTP supplements to help produce more serotonin (and thereby reduce depression), but they are not generally recommended for sleep.

Why am I so tired on Thanksgiving — is it really from the turkey?

Tryptophan or no tryptophan, nutrition experts believe that the feeling of lethargy and near coma you feel after your Thanksgiving meal is mostly a result of overeating.

“It is the dessert and alcohol — as well as the sweet cranberry relish, cornbread stuffing with chestnuts, and pecan pie that put you to sleep. Often the only vegetables are also starchy — e.g., sweet potatoes with marshmallows and brown sugar, and overcooked green bean casserole. Actually, there is a lot of turkey left over from the Thanksgiving feast — even with lots of people present. Thus, it is likely that the meal is very high in carbohydrates and low in protein,” says Susan Ettinger, an adjunct professor at Hunter College in New York City.

Additionally, according to Shelke, “fat requires assistance with digestion and a fat-laden meal [think turkey skin and gravy, ice cream and other rich desserts] usually redirects the blood to the digestive system. This deprives the brain of the usual flow of blood (and oxygen) and a brain with less blood and oxygen is also a sleep brain.”

What foods are high in tryptophan?

Tryptophan is found in poultry, meat, cheese, fish, eggs and seeds, and, in fact, turkey is not one of the foods with the highest amounts of tryptophan. There are many foods, such as pumpkin seeds, ground pork, cheddar, Swiss, provolone and mozzarella cheese, and yellowfin tuna that have more tryptophan per 100 grams than turkey.

▪ Cheese, mozzarella, low moisture, part-skim (132 grams, 1 cup, diced) 0.727 gram tryptophan

▪ Fish, yellowtail, mixed species, cooked, dry heat (146 grams, half a fillet) 0.485 gram tryptophan

▪ Seeds, sunflower seed kernels, oil roasted, without salt (135 grams, 1 cup) 0.413 gram tryptophan

▪ Turkey, all classes, back, meat and skin, cooked, roasted (140 grams, 1 cup, chopped or diced) 0.403 gram tryptophan

▪ Soybeans, green, raw (256 grams, 1 cup) 0.402 gram tryptophan

▪ Chicken, broilers or fryers, drumstick, meat and skin, cooked, stewed (140 grams, 1 cup, chopped or diced) 0.4 gram tryptophan

▪ Peanuts, Valencia, oil-roasted, without salt (144 grams, 1 cup) 0.379 gram tryptophan

▪ Pork, fresh, shoulder, whole, separable lean and fat, cooked, roasted (135 grams, 1 cup, diced) 0.375 gram tryptophan

▪ Beef, round, top round, steak, separable lean and fat, trimmed to  1/8-inch fat, prime, cooked, broiled (85 grams, 3 ounces) 0.298 gram tryptophan

▪ Nuts, almonds, dry roasted, without salt added (138 grams, 1 cup whole kernels) 0.288 gram tryptophan

This story was originally published November 23, 2015 at 1:50 PM with the headline "Diet Detective: Does turkey really make you sleepy?."