How exercise leads to sharper thinking and a healthier brain

To build a better brain, just exercise.

That’s the message of two important new studies of how physical activity changes our minds. In one, scientists delved into the lives, DNA and cognition of thousands of people to show that regular exercise leads to much sharper thinking.

Another study helps explain why exercise is good for the brain. Researchers found that just six minutes of strenuous exertion quintupled production of a neurochemical known to be essential for lifelong brain health.

The studies arrive at a moment when some recent, widely discussed research has been raising doubts about the extent to which exercise bolsters thinking and memory. But the new findings, which analyzed data for almost 350,000 people, make the strongest case yet that regular exercise can improve cognition.

These studies reinforce the idea that “absolutely, exercise is one of the best things you can do” for your brain, said Matthieu Boisgontier, an associate professor at the University of Ottawa, who oversaw one of the studies.

‘Miracle-Gro’ for your brain

The first inklings that exercise remodels brains and minds came decades ago in mouse studies. Active, running animals in these experiments scored much higher on rodent intelligence tests than sedentary mice, and their brain tissues teemed with elevated levels of a substance known as brain-derived neurotrophic factor or BDNF, often referred to as “Miracle-Gro” for the brain.

BDNF prompts the creation and maturation of new brain cells and synapses. It bulks up brains.

Studies in people have since established that exercise also raises BDNF levels in our bloodstreams, although it’s harder to look inside our brains and see if it rises there. Multiple, large-scale epidemiological studies, meanwhile, have linked more exercise to better memories and thinking skills and less risk for neurodegenerative diseases, such as Alzheimer’s.

Qualms have lingered, though, about just how potent exercise really is for our brains.

A study published last year of more than 500 older people found little cognitive benefit from 18 months of regular walking or other light exercise, while a major review of past research published in March pointed out that many human studies of exercise and cognition have been too small or otherwise limited to show persuasive benefits for brain health from working out.

In some scientific quarters, rumblings have begun about whether to continue recommending exercise as a way to maintain mental acuity with age, Boisgontier said. “But we say, ‘No, no. Don’t stop. Look at our findings first,’” he said.

A landmark brain study

The study from Boisgontier and his colleagues, published last week in Scientific Reports, uses a novel and complex type of statistical analysis to go beyond traditional observational research and firmly establish that exercise does improve your brain skills.

They turned to DNA and Mendelian randomization, a recently popularized method of using genetic variations to characterize and sort people. We each are born with or without certain snippets of DNA, some of which are known to contribute to a likelihood of being physically active. From before birth, we are, in effect, randomized by nature to be someone who is or isn’t prone to move. Other gene snippets play a similar role in cognition.

By cross-checking the cognitive scores of people who have or lack the exercise-promoting snippets against those of people with the gene variants related to cognition, scientists can discern the extent to which exercise contributes to thinking skills.

From two enormous databases of health information, they pulled genetic data for almost 350,000 people of all ages, along with objective measurements of physical activity for about 91,000 of them and cognitive scores for almost 258,000. People with a genetic predisposition to exercise typically did exercise, they found, and scored better on tests of thinking, if their exercise was at least moderate, comparable to jogging.

And, yes, you can get brain benefits from exercise even if you don’t have the gene snippets,.

The interplay of exercise and thinking was strong enough to indicate causation, Boisgontier said, meaning, in this big study, the right exercise resulted in sharper minds.

6 minutes of intense exercise raises BDNF

The other new study, although comparatively small, may help explain how exercise keeps your brain healthy.

In this experiment, 12 healthy, young people rode an exercise bike at a very leisurely pace for 90 minutes, followed by six minutes of intervals consisting of 40 seconds of all-out pedaling interspersed with 20 seconds of rest. Before, during and after each session, researchers tracked BDNF in people’s blood.

They also measured levels of lactate. Muscles release lactate, often called lactic acid, during exercise, especially if it’s strenuous. It can travel to and be sucked up by the brain as fuel.

Past studies in mice suggest this shift in brain fueling is what jump-starts the creation of BDNF. When animals’ brains begin slurping up lactate in lieu of sugar, they start pumping out more BDNF and the mice soon blossom into rodent brainiacs.

Now, the researchers found indications of something similar happening in people. During easy riding, lactate levels rose slightly in people’s blood after about 30 minutes, as did the amounts of BDNF in their blood. But during and after the six minutes of hard, fast pedaling, lactate soared and so did BDNF. (Another part of the study examined the effects of 20 hours of fasting, but it turned out to have no effects on BDNF.)

What these results suggest is that “exercise is good for your brain and that exercising longer, or particularly, harder, may maximize the benefits,” said Travis Gibbons, a postdoctoral fellow at the University of British Columbia at Okanagan, who led the study.

Boisgontier agreed. “Always, with exercise and the brain, it involves BDNF,” he said, adding that in his group’s study, both moderate and more-vigorous exercise - brisk walking and brisker running - improved cognition, presumably because they prompted a rise in BDNF.

Many questions remain, Gibbons pointed out, including how long BDNF stays elevated after exercise, the ideal types and amounts of exercise to up BDNF, and whether the effects are the same in older or less-healthy men and women, as well as why fasting didn’t increase BDNF in this experiment. He and Boisgontier have follow-up studies planned or underway.

But for now, this research tells us that exercise, fast or slow, should reliably protect our ability to think.

Gretchen Reynolds is the author of the “Your Move” column for The Washington Post. Reynolds is an award-winning journalist who has been writing about the science of exercise and health for more than 15 years, first at the New York Times and now at The Post.