Is exercise really good for the brain? Here’s What Science Says

The health benefits of physical activity are undeniable.

However, a recent study based on data published over the past 30 years challenges the famous adage Mens sana in corpore sano (a healthy mind in a healthy body) and questions the importance of exercise for both brain health and cognition.

Just days after the study was published, our team of health and neuroscience researchers published the results of our study of more than a quarter of a million people. Our results clearly support the beneficial effects of both moderate and vigorous physical activity on cognitive functioning, fueling an important scientific debate.

Who is right and who is wrong? Here’s what science says.

Is exercise useless for cognitive functioning?

The first study was published on March 27, 2023. It is a review of 24 meta-analyses that review data from 11,266 healthy people using a more rigorous approach.

Although nearly all of the 24 meta-analyses included in this review concluded that exercise had a positive effect on cognitive function, the authors argue that the analyzes performed were suboptimal. For example, they point out that both baseline levels of physical activity and the tendency of the scientific community to publish only significant results have rarely been taken into account. Once these adjustments were made, the authors found results suggesting that the benefits of exercise are actually lower than those estimated in previous meta-analyses and may even be negligible.

Based on these findings, the authors argue that public health agencies such as the World Health Organization (WHO) should no longer claim that physical activity improves cognitive health, academic achievement and executive function, at least until when more reliable scientific evidence does not accumulate.

Well, that proof didn’t take long to arrive.

Genetics and DNA to the rescue

The second study, ours, is a genetic study involving nearly 350,000 people, published four days later on March 31, 2023. Our findings provide scientific evidence of the cognitive benefits of moderate to vigorous physical activity.

This test is based on the two-sample Mendelian randomization method, which exploits the random variations in our DNA that occur at the moment of conception, before we are even born.

When two humans are compared, 99.9% of their genetic material is identical. DNA can be thought of as a long chain of building blocks, called nucleotides, that varies once every 1,000 building blocks between these two humans. There are four randomly arranged building blocks: thymine, adenine, guanine, and cytosine. Genetic variations can involve, for example, a cytosine brick in one place in one person’s DNA and a thymine brick in the same place in another.

The first sample of our study, consisting of 91,084 people, was used to identify genetic variations associated with differences in physical activity, as measured by motion sensors worn on the wrist.

The second sample of our study, consisting of 257,854 people, was used to test whether genetic variations associated with physical activity had a proportional effect on cognitive functioning. Since this was the case, we were able to conclude that there is a causal effect of physical activity on cognitive function.

Moderate exercise goes a long way

In our study, we demonstrate that physical activity improves cognitive functioning, but more importantly, that the effect of moderate physical activity (brisk walking, cycling) is 1.5 times greater than that of vigorous physical activity (running , basketball game). This finding highlights that we don’t need to drive ourselves to exhaustion to get cognitive benefits from exercise.

When all types of physical activity were considered together (including sedentary and light physical activity), our results no longer showed an effect on cognitive function. This finding confirms the importance of reaching at least moderate intensities to reap the cognitive benefits of physical activity.

Our findings are consistent with those of a recent study that emphasizes the importance of exercise duration and intensity for the release of a protein called BDNF in the brain. This protein is involved in making new neurons, new connections between these neurons, and new blood vessels to feed them.

This protein, whose production increases during exercise, is therefore one of the physiological mechanisms that explain the beneficial effects of physical activity on cognitive function. The very existence of this explanatory mechanism further strengthens the findings supporting a beneficial effect of exercise on brain functioning.

It’s never too late to start

Several differences may explain the discrepancy in results between the review of meta-analyses and our genetics-based study.

First, the review only looks at healthy people, which is not the case in our study. Second, our study distinguishes between light, moderate, and vigorous physical activity, whereas the review does not make this distinction. Finally, our genetic approach evaluates long-term, lifetime effects, while the review is based on interventions lasting between one month and two years.

Since we’re dealing with the temporal aspects of physical activity here, it’s important to remember that it’s never too late to start exercising. In fact, a 2019 study showed that starting to be active at a later age has the same overall positive health effects as being active throughout your life.

Conclusion: hasty decisions are never good

Based on our findings, it appears that physical activity can still be considered beneficial for brain health and cognition. Furthermore, in the current socio-political climate of distrust of science, we should not be jumping to conclusions based on a single study that contradicts years of research, but is based on the same data.

As is often the case in science, it is wiser not to rush into decisions but to wait for further studies before suggesting changes to physical activity guidelines. The accumulation of converging evidence from different research groups should be a prerequisite for changing public health messages. As this article shows, we are nowhere near that point, and the benefits of physical activity on a broad range of physical and mental health outcomes remain undeniable.

Matthieu P.BoisgontierAssociate Professor, Faculty of Health Sciences, LUniversit dOttawa/University of Ottawa and Boris Cheval, Senior Researcher, Swiss Center for Affective Sciences, Universit de Genve

This article is republished from The Conversation under a Creative Commons license. Read the original article.