The Claim

In adolescent male athletes of Brazilian descent, acute ingestion of caffeine at 6 mg/kg significantly improves endurance performance and aerobic power (VO2max) in individuals with the ACE gene I allele (DI or II genotypes), but not in individuals with the DD genotype, indicating a genotype-dependent ergogenic response to caffeine during high-intensity intermittent exercise.

Source: ACE gene polymorphisms (rs4340) II and DI are more responsive to the ergogenic effect of caffeine than DD on aerobic power, heart rate, and perceived exertion in a homogeneous Brazilian group of adolescent athletes

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
58score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Cause and effect
1 study reviewed
In plain English

In adolescent male athletes of Brazilian descent, consuming 6 mg of caffeine per kilogram of body weight increases endurance performance and VO2max only in those with the ACE gene I allele (DI or II genotypes), not in those with the DD genotype.

See the scientific wording

In adolescent male athletes of Brazilian descent, acute caffeine ingestion at 6 mg/kg significantly improves endurance performance and aerobic power (VO2max) in individuals carrying the ACE gene I allele (DI or II genotypes), but not in those with the DD genotype, suggesting a genotype-dependent ergogenic response to caffeine during high-intensity intermittent exercise.

Why this might work

People with a specific gene version have more slow-twitch muscle fibers that use oxygen efficiently. When they take caffeine, it blocks signals that make the brain and muscles feel tired, which lets them work harder and longer. The caffeine also helps these fibers burn fat for energy, boosting their ability to sustain high-intensity exercise and increasing how much oxygen they use.

Verified mechanismbased on 1 study

What the research says

1 study

  1. Study: ACE gene polymorphisms (rs4340) II and DI are more responsive to the ergogenic effect of caffeine than DD on aerobic power, heart rate, and perceived exertion in a homogeneous Brazilian group of adolescent athletes

    In young Brazilian male athletes, caffeine made those with a certain gene version (I allele) much better at endurance sports and using oxygen, but didn’t help those without it — meaning your genes can change how well caffeine boosts your sports performance.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

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