Tryptophan

Tryptophan is an essential amino acid (supplied by the diet). Its particularity: it is the starting point for the synthesis of serotonin (the well-being neurotransmitter) and then melatonin (the sleep hormone). It also feeds the vitamin B3 (niacin) pathway.

The original angle (the turkey dinner paradox and getting into the brain): the popular myth says that turkey (rich in tryptophan) makes you drowsy after a festive meal. The reality is more subtle.

Tryptophan has to cross the blood-brain barrier to act on the brain, but it competes with other amino acids for the “transporter”. Paradox: a very high-protein meal (rich in tryptophan) ALSO supplies lots of other competing amino acids, so tryptophan struggles to get through.

A counter-intuitive tip: it is carbohydrates that help tryptophan enter the brain! By stimulating insulin, carbohydrates push the competing amino acids into the muscles, leaving tryptophan “alone” to pass into the brain. This is why a carbohydrate-based meal in the evening (or combining tryptophan with a little carbohydrate) is thought to favour serotonin/melatonin and falling asleep, more than a purely protein meal.

Practical application for sleep: a dinner including a source of tryptophan (turkey, eggs, dairy products, banana, pumpkin seeds) with complex carbohydrates, a few hours before bed, can support melatonin production. Cofactors (magnesium, vitamin B6) help the conversion.

The microbiota link: the microbiota influences tryptophan metabolism (some bacteria divert it towards other pathways). A healthy microbiota supports the production of serotonin from tryptophan.

Sources: turkey, chicken, eggs, cheese, fish, pumpkin/sunflower seeds, tofu, banana, dark chocolate, oats.