Phenylethylamine Levels May Explain Link Between Exercise and Mood

Originally published by Reuters Health, October 1, 2001

WESTPORT, CT — There is growing evidence that regular exercise boosts people's moods and may even help protect against depression. Now UK researchers report that phenylethylamine levels may help explain this relationship.

Aerobic activity appears to elevate the body's levels of phenylethylamine, Dr. Ellen Billett and colleagues at Nottingham Trent University report the Friday issue of the British Journal of Sports Medicine.

Dr. Billet's group found that the average phenylethylamine concentration in the urine of 20 healthy young men increased by 77% after the subjects ran on a treadmill for 30 minutes. The study participants refrained from activity for 1 day, and then repeated the exercise the next day. Urine samples collected during the inactive and active days were then compared.

For 18 of the 20 men, urine phenylacetic acid—which reflects phenylethylamine levels—was higher after exercise, increasing anywhere from 14% to 572%. Because the chemical is similar in some ways to amphetamines, the researchers speculate that phenylethylamine may play a role in the "runner's high."

In addition, the report indicates, research conducted with patients who have depression and bipolar disorder has shown that these individuals have below normal levels of phenylacetic acid in the urine.

Based on these findings, Dr. Billett and colleagues suggest that the effects of exercise on phenylethylamine levels be investigated in patients diagnosed with depressive disorders.