Myths vs facts: TCF7L2 and longevity

TCF7L2 is a transcription factor strongly associated with type 2 diabetes risk in GWAS. Its link to longevity is indirect: diabetes shortens lifespan, so risk variants may reduce healthspan. A myth is that TCF7L2 directly controls aging – no evidence supports that. The fact is that it influences glucose metabolism and insulin secretion. Effect size on diabetes risk is moderate (OR ~1.4), but effects on lifespan are small and heavily modified by lifestyle. Consumer tests marketing TCF7L2 as a 'longevity gene' overstate clinical utility. A single test result does not justify specific diets or supplements. Evidence: human-strong for diabetes, human-moderate for longevity. Caveat: most tested SNPs are common variants with low penetrance.