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Charles Platkin

The Diet Detective 

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.

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.

The National Sleep Foundation says, “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.”

Some scientists believe that tryptophan from food sources (no matter what other foods you eat with it) doesn’t cross the blood-brain barrier.

Simon Young, Ph.D., a research psychologist at McGill University, said, “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.

“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,” Young said.

According to the National Center for Complementary and Integrative Health (NCCIH), “Dietary supplements containing chemical precursors of melatonin (L-tryptophan and 5-hydroxytryptophan [5-HTP]) have been researched as sleep aids, but they have not been shown to be effective for insomnia.

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 — not to mention the boring relations,” says Susan Ettinger, Ph.D, RD, an adjunct professor at Hunter College in New York City.

Additionally, “Fat requires assistance with digestion and a fat-laden meal 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 sleepy brain.”

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Charles Platkin PhD is a nutrition and public health advocate and founder of Sign up for the free Diet Detective newsletter at


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