Smoking accelerates biotin catabolism in women.

BACKGROUND Smoking accelerates the degradation of many nutrients, including lipids, antioxidants, and certain B vitamins. Accelerated biotin catabolism is of concern in women because marginal biotin deficiency is teratogenic in mammals. OBJECTIVE The objective was to assess the effect of smoking on the biotin status of women. DESIGN A preliminary study of 7 women and 3 men examined the urinary concentrations of biotin and its metabolites biotin sulfoxide and bisnorbiotin in smokers. The interpretation of the results of this study was limited by the lack of a contemporaneous control group; consequently, we conducted a cohort-controlled study. Smoking women (n = 8) and nonsmoking control subjects (n = 15) provided 24-h urine samples; excretion rates of biotin, the biotin metabolites, and 3-hydroxyisovaleric acid were determined. Increased urinary excretion of 3-hydroxyisovaleric acid, which reflects a reduced activity of the biotin-dependent enzyme 3-methylcrotonyl-Co A carboxylase, is a sensitive indicator of biotin depletion at the tissue level. RESULTS Compared with control subjects from previous studies, the smoking women in the preliminary study excreted significantly less urinary biotin (P = 0.02). Moreover, the ratio of urinary biotin sulfoxide to biotin increased (P = 0.04) in these women. In the cohort-controlled study, the urinary excretion of biotin decreased by 30% (P = 0.04), and the ratios of urinary bisnorbiotin and biotin sulfoxide to biotin increased significantly, which indicated accelerated catabolism in smokers. Moreover, the urinary excretion of 3-hydroxyisovaleric acid was greater in the smokers than in the control subjects (P = 0.04), which indicated biotin depletion in the smokers at the tissue level. CONCLUSION These data provide evidence of accelerated biotin metabolism in smoking women, which results in marginal biotin deficiency.