Working out could boost the immune system by releasing ‘regulatory’ T cells – that fight heart disease, cancer, diabetes and dementia

The benefits of exercising may partly be due to the way that being active enhances the immune system, scientists have suggested.

Researchers at Harvard Medical School found that exercise triggers the release of regulatory T cells, also known as Tregs, which enhance the muscles’ ability to use energy as fuel and improve endurance.

These same cells are also known to play a role in countering inflammation linked to a range of health problems – including cardiovascular disease, cancer, diabetes and dementia.

Most previous studies on human performance have focused on the role of hormones released during exercise and their effects on different organs, but this fresh research is one of the first to show how the immune system may play a role.

‘The immune system, and the Treg arm in particular, has a broad impact on tissue health,’ says Professor Diane Mathis of Harvard Medical School.

Although the findings relate to observations in lab mice, researchers say the study is an important step towards understanding molecular changes that occur during exercise that provide health benefits.

Exertion is known to temporarily damage muscles, causing a cascade of inflammatory responses. In the study, the team analysed cells taken from the hind-leg muscles of mice that ran on a treadmill just once as well as those that ran regularly. These were then compared with the muscles of sedentary mice.

The sets of both cells belonging to the mice that ran on treadmills showed classic signs of inflammation, and also had elevated levels of Tregs in their muscles – which lowered the exercise-induced inflammation. Neither change was observed in the sedentary mice.

However, further Treg benefits caused by exercise – such as improved muscle performance – were seen only in the regular treadmill runners, which matches established findings in humans that regular activity is required to confer gains over time.

The Harvard experts also suggest that another role of Tregs is to counter the harmful effects of interferons – proteins released as part of the body’s inflammatory response.

‘With exercise, we have a natural way to boost the body’s immune responses to reduce inflammation,’ Prof Mathis adds. ‘It’s possible exercise is boosting Treg activity elsewhere in the body as well.’