Alteration of human pain thresholds by nutritional manipulation and L-tryptophan supplementation.

Pain perception and tolerance thresholds of 30 normal subjects were determined by electrical stimulation of dental pulps before and after dietary manipulation which included either tryptophan supplementation or placebo. Perception threshold levels were similar in tryptophan and placebo subjects; however, pain tolerance levels were significantly higher in the group receiving tryptophan. Side effects such as nausea, skin itching, weight loss and mood elevation were more common in the tryptophan group than in the placebo group.