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Thursday, 27 September, 2001, 00:50 GMT 01:50 UK
Why exercise cheers you up
Exercise benefits the mind as well as the body
Exercise benefits the mind as well as the body
Scientists may have identified a chemical which could explain why exercise is an anti-depressant.

Until now, it has not been clear why exercise has that effect.

But, doctors from Nottingham Trent University suggest the chemical phenylethylamine could play a part.

Phenylethylamine is a naturally produced chemical that has been linked to the regulation of physical energy, mood and attention.

Physical exercise has a valid place in the treatment and prevention of some mental health problems

Spokeswoman for Mind
An enzyme changes the chemical into phenylacetic acid. There is evidence that levels of both substances are low in the biological fluids of depressed patients.

In what are thought to be the first attempts to test the effects of exercise on levels of the chemical, the researchers found, overall, levels of the acid increased by 77% after exercise.


Twenty healthy men, with an average age of 22 were tested.

All regularly did around four hours of moderate to hard aerobic and anaerobic exercise each week.

Before the study began, they refrained from exercise for a day, and a urine test was done to check for levels of levels of phenylacetic acid, the most accurate measurement of the chemical.

The next, the men exercised on a treadmill at 70% of their maximum heart rate capacity for 30 minutes.

Doctors chose that level because mood changes are commonly reported at that level.

The men were also asked to rate how hard they had found the exercise.

When urine levels were checked, it was found phenylacetic acid levels were increased in 18 out of the 20 participants.

Though the average increase in levels was 77%, the increases in individuals ranged from 14 to 572%.

But the highest rises were seen in two out of the three who had rated the exercise as hard

Research possibilities

The research team say though there may be many factors involved in the phenylacetic acid response, because its chemical structure is very similar to that of amphetamines, it may be that this chemical is part of a "runner's high", a phenomenon linked to natural endorphin activity in the brain.

They suggest phenylacetic acid could also be important because it can cross from the blood to the brain, something endorphins cannot do.

Dr Ellen Billet, who was one of the team of researchers from Nottingham Trent who carried out the research, told BBC News Online: "We felt there may be an effect of exercise on phenylethylamine."

GPs can prescribe a drug based on the chemical which is known to have beneficial effects on patients.

Dr Billet said: "We also know that moderate exercise has these beneficial effects.

"So we wondered 'what if this was how exercise works'".

She said more research needed to be done to develop their initial finding, including why different people's phenylethylamine levels are affected in different ways by exercise and if different kinds of exercise have the same effects.

But she said people should still exercise, because of its benefits on both mental and physical health.

"This could be used as and adjunct."

A spokeswoman for the mental health charity Mind said: "Physical exercise has a valid place in the treatment and prevention of some mental health problems.

"In a recent Mind survey of Cannons gym users, 75 % said they exercised to reduce their stress levels and 67% said they used exercise to maintain their mental health, like lifting 'low' moods.

"Mind is calling for all GPs to offer exercise sessions on prescription to patients with mental health problems, particularly as we know that most people with mental health problems don't know this non-drug 'treatment' option exists."

The research was published in the British Journal of Sports Medicine.

See also:

20 May 01 | Health
Exercise 'helps mental health'
09 May 01 | Health
Walking 'slows mental decline'
05 Apr 01 | Health
Exercise on prescription
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