Evidence check: CYP2D6 in the context of Schlaf

The claim that a DNA test for CYP2D6 in the context of sleep can guide a perfect diet or supplementation is not scientifically supported. CYP2D6 is a phase I drug-metabolizing enzyme relevant for processing medications (e.g., antidepressants, beta-blockers), not for sleep or nutrition. No robust human RCTs show a significant effect of CYP2D6 variants on sleep quality or nutrient requirements. GWAS effect sizes are minimal, and clinical utility for daily life is unproven. Consumer tests often overstate the importance of such variants. Evidence grade: gwas. Caution: Supplementation or dietary changes based on CYP2D6 are not recommended and may lead to unnecessary costs or risks. For sleep issues, lifestyle factors (sleep hygiene, stress, light exposure) are far more relevant than a single gene.