Cognitive enhancement has become a popular theme in the self-improvement world. There are lots of claims for various supplements, brain training programs, apps, and lifestyle interventions that will, allegedly, make you smarter and keep the (approximately) three pounds of grey and white matter inside your skull functioning better for longer.

This isn’t just driven by a popular desire to be the next Albert Einstein. As people are living longer, tragically there is also an increase in the number of people living with dementia and neurodegenerative diseases. Not only does the body tend to break down and develop problems as we get older, but the brain does too, having a profound effect on a person’s quality of life, and even their personality. Those of us who have had a family member afflicted are aware of how awful these conditions can be, and are often keen to try anything that might improve our own odds.

So, does any of it actually work? Brain training programs that involve practicing quick thinking and various kinds of puzzle solving might make intuitive sense – but the evidence for their effectiveness is (somewhat depressingly) thin on the ground. On the other hand, one of the most promising interventions for improving brain function may at first glance not seem to have much to do with brains at all.

We’ve been aware for some time that exercise can be beneficial for mental health in some people with conditions like as anxiety and depression. More recently, claims that exercise can help with brain function even more widely have become commonplace. It’s often now touted on health websites and in fitness magazines that certain kinds of workouts can make you smarter and reverse age-related “cognitive decline,” as well as boosting your mood.

What is the evidence linking exercise and brain health?

At first glance, it’s easy to be skeptical. Isn’t this just another one of those scenarios where correlation can be mistaken for causation? Perhaps people with better brain health have more willpower and are more likely to exercise in the first place, skewing the statistics?

Fortunately, the research on this topic doesn’t just come from observational studies, where people are asked about their exercise habits, have their fitness levels tested, and then these are compared with various scores for brain function. There have also been a decent number of randomized controlled trials that have also found exercise to be an effective way of improving brain function in older people. Randomized controlled trials systematically compare the effects of an intervention with a control condition on a group of volunteers who are randomly allocated to the different groups. The aim is to eliminate as many possible sources of bias as possible so that any statistical difference between the groups can be attributed to the effect of the intervention being tested. Systematic reviews have looked at whole collections of these studies and concluded that there is, in fact, a robust effect going on.

How does it work?

Researchers admit that more work needs to be done to pin down all the mechanisms involved in the link between exercise and brain health. It is currently thought that one key factor is the ability of exercise to affect energy metabolism in a number of ways. In particular, exercise improves the blood flow to certain key areas of the brain and stimulates the release of Brain-Derived Neurotrophic Factor (BDNF). BDNF is a protein that is involved in the growth of new synapses (connections between brain cells), as well as helping to ensure the survival of existing ones. For a long time, people believed that it was impossible for people to grow new brain cells. They thought that you were born with all the brain cells you’d ever have, and then it was all downhill from there as they died off. This turned out not to be the case, and much research is being done into the conditions under which neurogenesis (the formation of new brain cells) can take place. Exercise and BDNF have a role to play in this process, too; it has been noted that this happens particularly in the hippocampus, an area of the brain involved in memory.

There are many other possible biological reasons for the link between exercise and brain function, and no doubt we’ll be hearing more about some of these in the future.

What about brain function in younger people?

A lot of the research on this subject looks at brain function in aging populations, at least in part because this is a crucial public health concern. But what about the effects of exercise on your brain when you’re younger? Do you have to wait until old age to reap the benefits? Current thinking is that exercise tends to lead to greater benefits later in life, because it is better for preventing age-related deterioration than it is at improving your abilities while they’re already at their peak. However, a few studies suggest that there may also be some shorter-term benefits. In addition, some research on the effects of exercise on cognitive development in children suggests that certain types of exercise may improve some aspects of brain function and development.

What type of exercise is best for the brain?

Much of the research that has been done so far focuses on aerobic exercise (predominantly walking), and there are good reasons to think that this kind of exercise is particularly good for improving metabolic function and blood flow as well as stimulating the release of BDNF. However, some studies looking at the effects of resistance training on aspects of cognitive function have also found positive results, especially among older people. Current advice is that a combination of both aerobic and strength training is likely to provide the most benefit.

The verdict: TRUE

Compared to many of the things we’ve looked at in this column, the evidence that exercise is good for your brain is unusually consistent, and the effect seems to be quite significant. If you like solving puzzles, then a brain training app might be fun, but if you want to improve your odds of keeping your brain healthy into old age, then you’re better off spending your money on that gym membership or a pair of running shoes.