Is Exercise Brain Food?
THE PHYSICIAN AND SPORTSMEDICINE - VOL 28 - NO. 11 - NOVEMBER 2021
Research has shown that exercise protects against an array of chronic diseases and slows the effects of aging. Exercise also improves certain psychological traits, such as "affect," energy levels, and mild-to-moderate depression. But does exercise affect raw thinking power—capacities such as planning and learning?
Studies that support the effect of exercise on cognitive function have not been as plentiful as those establishing its effects on other aspects of human health. However, some intriguing findings have recently been published. Van Praag et al (1) demonstrated that adult mice who exercised on a wheel were more effective learners than sedentary mice. The mice, which hate to swim, were trained for 6 days to locate a slightly submerged platform in a murky, mouse-size pool. After training, the exercising mice swam straight to the platform when released into the pool, while the sedentary mice took wandering paths and longer times to find the refuge. The exercising mice also had 2.5 times the growth of new neurons in the dentate gyrus, an area believed to be important in memory.
According to Arthur F. Kramer, PhD, a psychologist and faculty member in the Beckman Institute Human Perception and Performance Group in Urbana-Champaign, Illinois, parallels are emerging between animal and human studies, although positive correlations between exercise and cognitive function are still open to debate. Last year, Kramer et al (2) studied the effects of exercise on "executive control processes" in 124 previously sedentary adults 60 to 75 years old. They found that the group that improved their aerobic fitness (VO2 max) by walking experienced significant improvements in thought processes such as planning, scheduling, and working memory—all of which depend, in part, on the integrity of the prefrontal and frontal cortex. A follow-up study is underway that will correlate changes in behavioral and fMRI activation patterns with changes in fitness.
The neurochemical and cellular mechanisms involved in cognitive changes are unclear, but animal studies give clues (3). In rats, improved aerobic fitness promotes the development of new capillary networks (4), enhances cortical high-affinity choline uptake, increases dopamine receptor density (5), and increases brain-derived neurotrophin factor gene expression (6).
It is intriguing to think that exercise might enhance cognitive functioning, even in the formerly sedentary. The implications could be far-reaching, especially for older people.
Of course, it is too early to judge the strength of the linkage and the degree of impact of exercise on brain function. I look forward to additional studies that may document this relationship. But many people eat special diets and consume supplements for which there is even less available evidence, all in the hope of increasing memory and cognitive functioning. Physicians should be aware of this potential benefit of exercise.