Myths vs facts: ACTN3 and fertility

The claim that the ACTN3 gene (the 'speed gene') affects fertility is a myth unsupported by evidence. ACTN3 encodes alpha-actinin-3, a protein in fast-twitch muscle fibers, and is linked to athletic performance – not reproduction. No reproducible studies show a causal or even associative relationship between ACTN3 variants and fertility outcomes like egg quality, sperm function, or hormone levels. The confusion likely stems from marketing that overextends genetic findings from sports into unrelated health domains. Fertility is governed by a complex interplay of hormones, environment, lifestyle, and many other genes (e.g., FSH receptor, AMH). An ACTN3 test tells you nothing about your fertility. For reproductive health, rely on validated biomarkers and medical guidance, not muscle-gene tests.