Risks and limits of DNA Test Basis

DNA tests for diet and health (e.g., MTHFR, VDR, NutriCare) often provide weak or population-specific associations that do not justify clinical action. Official guidelines do not recommend changing supplements (e.g., folic acid vs. methylfolate) or diet based solely on a SNP. The DIETFITS trial (JAMA 2018) refuted genotype-based low-fat/low-carb assignment, and the AHA and ACMG warn against overinterpreting direct-to-consumer tests. IgG tests indicate food exposure, not intolerance, and are not validated for weight loss. Blood biomarkers (vitamin D, homocysteine) are more reliable than DNA alone. Many products use marketing language ('inspiration') to avoid medical claims. Overall evidence is mixed: some gene-diet interactions (APOA2, FADS) have mechanistic or population-based support, but effect sizes are small and not causal. Consumers should view DNA tests as complementary information, not a basis for medical decisions.