How to get serotonin in your diet

Serotonin is manufactured in the body from the amino acid tryptophan, which is present in most protein-based foods. High levels of tryptophan are found in cheese, meat, soya beans, sesame seeds, chocolate, oats, bananas, dried dates, milk and salmon.

Turkey is reputed to contain high quantities of the amino acid, which is said to account for the air of contentment that reigns immediately after Christmas dinner. But analysis shows that turkey contains only marginally more than chicken, pork or beef – and somewhat less than cheese.

Tryptophan is sold in healthfood stores as a dietary supplement that is claimed to act as "nature's tranquilliser", boosting serotonin levels and making us happier, calmer and less stressed. Its sleep-inducing properties are, however, more likely to be linked with the quantity of food eaten than the amount of tryptophan it contains – as the near-universal urge to snooze after a large meal confirms.