It's well established that exercise can affect mental as well as
physical capacities. However, your genotype (genetic makeup) may play a
surprisingly large role in determining just how much influence exercise can
have on your cognitive abilities. David Bucci and his colleagues from Dartmouth
College ran some experiments to demonstrate this fact.
Fifty-four healthy, sedentary young adults completed their study.
All participants underwent genetic testing to determine which type of brain-derived neurotrophic factor (BDNF) they had. BDNF, a protein involved in stimulating
neuron growth and known to increase with exercise (at least in rats) comes in various flavors, or alleles. The most common alleles
encode either a valine (Val) or a methionine (Met) at position 66 of the
protein. A single base pair change in the DNA determines which of these types
of BDNF a person will make.
On day one of the study, volunteers were assessed for
physical fitness. They were then given a ‘novel object recognition’ (NOR) test
that consisted of two parts. First, they were shown a set of 50 images, one by
one. They next took a fifteen-minute break to fill out a mental health questionnaire.
Finally, they were shown 100 images, half of which they had seen before and
half of which were brand new pictures. Their task was to distinguish between
the two.
The participants were then divided into groups and told to
return in four weeks. One group was instructed to continue not exercising at
all (control). A second group was asked to exercise for at least 30 minutes
four times a week. This group was further divided into two, one of which also
exercised on the final test day (4W+) and one of which did not exercise that
day (4W-). A last group remained sedentary for the entire four weeks but did
exercise on the final test day (0W+). The participants all wore
pedometers to prevent cheating.
Four weeks later, physical fitness exams and NOR tests were
repeated. The only group to show improvement in the final NOR test was the 4W+
group. These were the people who had exercised for four weeks and on test day. It’s
no great surprise that regular exercise improves cognitive function. But here’s
the fascinating part. When the 4W+ group was further divided by genotype, it
turned out that only those who were homozygous for the Val allele (meaning
neither of their two copies of BDNF contained methionine at position 66) showed
improvement. Met carriers did not show improvement.
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