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.