Exercise detoxes body of depressive chemicals, scientists find

Exercise detoxes body of depressive chemicals, scientists find

The benefits of going for a run to alleviate stress after a tough day in the office are well known. But a new study has found out why working up a sweat is so relaxing and mood-boosting. Exercise actually detoxes harmful chemicals from the body and can alleviate depression.

Researchers at the Karolinska Institute in Sweden have discovered that physical activity purges the blood of a substance which accumulates during stress and can be harmful to the brain. Previous studies have suggested that people feel more positive after exercise because it releases a rush of endorphins. But it now appears that during exercise, the muscles begin to act like the liver or kidneys and produce an enzyme which clears out a molecule linked to depression. The team is hopeful that eventually a pill could be produced which would trigger the same effect to help the mentally ill.

"Our initial research hypothesis was that trained muscle would produce a substance with beneficial effects on the brain,” said Dr Jorge Ruas, principal investigator at the Department of Physiology and Pharmacology.

“We actually found the opposite: well-trained muscle produces an enzyme that purges the body of harmful substances. So the muscle's function is reminiscent of that of the kidney or the liver.”

Dr Ruas said cardiovascular exercise would probably have the biggest impact on mood and reducing stress.

“It is possible that other kinds of exercise will also have an effect, like resistance training such as weight lifting. But our results support the use of aerobic exercise like biking and running.

“Skeletal muscle appears to have a detoxification effect that, when activated, can protect the brain from mental illness.”

The study also demonstrates why people who do not exercise end up feeling sluggish, depressed and are more prone to disease.

GPs can currently prescribe exercise for depression, but are far more likely to prescribe anti-depressants. There were 53 million prescriptions were issued for antidepressants in England alone last year, nearly double the number prescribed a decade ago.

“Our modern, sedentary lifestyles that don’t include sufficient physical activity, might have made us mode susceptible to diseases such as stress-induced depression,” Dr Ruas added.

"Physical exercise is already prescribed as a therapy or co-therapy for mild to moderate depression. We think that our findings will help support the use of physical exercise in the prevention and treatment of depression."

Researchers had known that the protein PGC-1α1 increases in skeletal muscle during exercise but were unclear about what it was doing.

The team genetically engineered mice to have high levels of the protein and then exposed them, and a control group of normal mice, to a stressful environment of loud noises and flashing lights.

They found that after five weeks the normal mice had become depressed but the engineered mice appeared to be protected.

It is thought that the protein produces an enzyme called KAT which turns the harmful kynurenine molecule into harmless kynurenic acid which can be passed easily out of the body.

"In neurobiological terms, we actually still don't know what depression is,” said Mia Lindskog, a researcher at the Department of Neuroscience.

“Our study represents another piece in the puzzle, since we provide an explanation for the protective biochemical changes induced by physical exercise that prevent the brain from being damaged during stress.”

The study was published in the journal Cell.

By Sarah Knapton,

The Telegraph, Thursday 25 September 2014

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