Evidence check: CYP1A2 in the context of Sport

CYP1A2 is the primary enzyme responsible for caffeine metabolism. The common variant rs762551 (often called *1F) classifies individuals as fast (AA) or slow (AC/CC) metabolizers. In sports, it is hypothesized that fast metabolizers gain greater ergogenic benefit from caffeine, while slow metabolizers may face increased side effects like palpitations or sleep disruption. However, the evidence is mixed: some studies report improved endurance performance in AA homozygotes, but others find no genotype-dependent effect. Additionally, CYP1A2 activity is influenced by smoking, medications, and diet, which limits the predictive value of a single DNA test. Recent reviews (e.g., PMID: 30926990) conclude that current data do not support personalized caffeine dosing based solely on CYP1A2 genotype. For consumers, this means the test may offer a suggestive clue but not a reliable action plan. Safety note: high caffeine intake can be harmful regardless of genotype. Evidence: mixed.