Exercise improves cognitive function and reduces the risk neurodegenerative diseases such as Alzheimer’s disease. Some of these benefits are mediated by brain-derived neurotrophic factor (BDNF). Findings from a 2012 study showed that regular exercise improved cognitive function and increased BDNF levels, but a genetic variant in BDNF influenced the degree of these effects.

BDNF is a protein that acts on neurons in the central and peripheral nervous systems. A single-nucleotide polymorphism (SNP) in the gene that encodes BDNF causes a substitution of the amino acid valine (Val) by methionine (Met) in the BDNF protein. This genetic variant, known as Val66Met, alters exercise-driven release of BDNF and affects learning, memory, and emotion.

The intervention study involved 75 sedentary, healthy, young adults between the ages of 18 and 35 years. The participants took memory tests and mental health surveys before and after engaging in their randomly assigned respective activities: no exercise; four weeks of exercise with exercise and a test on the last day; four weeks of exercise, without exercise on the final test day; or a single bout of exercise on the last test day.

The participants who engaged in exercise showed improvements in memory and experienced lower levels of perceived stress, but only if they exercised for four weeks including the final day of testing. Participants who engaged in a single bout of exercise showed no changes in memory performance and demonstrated higher perceived stress levels. The authors of the study noted improvements in the participants' memory only if they did not carry the Val66Met variant, suggesting that the associated reduction in BDNF release attenuated some of the cognitive benefits of exercise. They also noted that the improvements in cognitive function were not correlated to improvements in mental health.

These findings suggest that the variable effects of exercise on brain function are related to a genetic variant that influences the production of BDNF.

• Link to full study.