The substance is phenylethylamine, or PEA, a natural stimulant produced by the body. It is related to amphetamines but does not have the long-lasting effects that make "speed" or "ice" such deadly drugs.
Now a British research team reports early findings suggesting that moderate exercise increases PEA levels for most people. They argue that this increase causes the euphoric mood often called "runners' high." And because depressed people tend to have low PEA levels, the researchers say there now is an explanation of why exercise has a natural antidepressant action.
"We are not advocating PEA as a drug," study author E. Ellen Billett, DPhil, tells WebMD. "What we are trying to say is now there is more chemical evidence for why runners' high occurs. We hope this information might give doctors more confidence in prescribing exercise for mild depression and as an adjunct to drug therapy."
The Nottingham Trent University research team studied 20 healthy young men. The men had their PEA levels measured after one day of no exercise and after one day of moderate exercise (30 minutes on a treadmill at 70% of their maximum heart rate).
All but two of the men had increased PEA levels 24 hours after their exercise. The amount of PEA increase varied from person to person. Interestingly, only three of the men rated the exercise as "hard," and two of these men had the greatest increase in PEA.
Hector Sabelli, MD, PhD, studied PEA while a professor at Chicago's Rush University. Now director of the Chicago Center for Creative Development, Sabelli says that the new findings fit exactly with all of his own experiments.
"What we have seen is that PEA metabolism is reduced in people who are depressed," Sabelli tells WebMD. "If you give PEA to people with depression, about 60% show an immediate recovery -- very fast, a matter of half an hour."
So what about the natural substances called endorphins, which have previously been linked to runners' high? Billett says that endorphins don't penetrate the brain as easily as PEA does -- so she thinks PEA may be the true basis for the good mood one gets from a workout. Sabelli is not so quick to rule out endorphins, however, and says that the natural compounds probably interact in various ways.
"We think PEA is part of the reward of exercise," Billett says, adding that it might be affecting other brain chemicals and that it's Iikely there are normal differences between individuals. "Some will respond to exercise, some won't."