Consuming tryptophan, the essential amino acid, may help people be more sure of themselves, according to a report.

People who consumed 3 grams of tryptophan daily were more confident and less quarrelsome than they were when taking an inactive placebo.

Tryptophan is an important precursor to the brain chemical serotonin, which helps regulate mood. For example, moderate dieting is known to lower blood levels of tryptophan, which may alter serotonin levels in the brain.

Low serotonin has been found to be related to depression, impulsivity and aggression.

Researchers recruited 98 healthy volunteers who were split into two groups. One group took 1 gram of tryptophan with each meal for 12 days, while the other group took a placebo pill.

At the end of 12 days, both groups received no treatment for 2 days and then switched pill types for another 12 days. During the entire study period, the men and women completed daily questionnaires that assessed various mood states and behaviors.

The absence of a consistent effect on mood is consistent with other studies that have shown that tryptophan may enhance mood in depressed individuals.

Agreeable and dominant behaviors are more common in most people's social repertoire than quarrelsome or submissive behaviors.

When taking tryptophan dominant behaviors increase further in frequency and quarrelsome behaviors decrease in frequency, the researcher concluded. It is particularly interesting to note that daily peaks of quarrelsome behaviors decreased.

Neuropsychopharmacology August 2001;25:277-289