Mar 24, 2018
Not for Everyone

Many athletes feel that consuming caffeine helps them perform better in competitions. But is this true? A new study on the genetics of caffeine metabolism has found that drinking caffeine might help some athletes but hinder others.

According to an article from The New York Times, Ahmed El-Sohemy, PhD, a Professor of Nutritional Science at the University of Toronto in Canada, began the study by swabbing the cheeks of about 100 young, male athletes. Dr. El-Sohemy and his team then analyzed this swab for variations of the CYP1A2 gene, which controls the expression of an enzyme that affects the breakdown and removal of caffeine from the body, to place the athletes into three different groups.

The first group was made up of fast caffeine metabolizers. These athletes had two copies of a variation of the CYP1A2 gene — one from each parent — that causes the body to rapidly metabolize caffeine. For these athletes, caffeine gives them a quick blast of energy but is gone just as fast. The second group was made up of moderate metabolizers. These athletes had only one copy of the faster-metabolizing CYP1A2 variant, as well as another variant that slows caffeine metabolism. The third group was made up of slow metabolizers — athletes with two copies of the slower-metabolizing gene variant.

Once separated into these groups, the researchers had the athletes take a low dose of caffeine — two milligrams for every kilogram of bodyweight. Then, they pedaled a stationary bike as fast as possible for 10 kilometers. The athletes then rode the same distance after taking twice as much caffeine and finished with a third session after taking a placebo.

Results from the study showed that the fast metabolizers rode seven percent faster after taking the largest dose of caffeine than they did with the placebo. Athletes who were moderate metabolizers performed the same throughout, and the slow metabolizers rode 14 percent slower after the high dose of caffeine than after the placebo.

According to Dr. El-Sohemy, this discrepancy most likely occurred because the caffeine stayed in the body of the slow metabolizers longer. This narrowed their blood vessels, which reduced the flow of blood and oxygen, caused their muscles to tire, and slowed their time. This didn’t happen to the fast metabolizers, as the caffeine exited the body before it could affect the blood vessels in this negative way. As a result, they were able to bike faster.

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