Association between vitamin B12-containing supplement consumption and prevalence of biochemically defined B12 deficiency in adults in NHANES III (Third National Health and Nutrition Examination Survey).

Objective: To explore the association between vitamin B 12 (B 12 )-containing supplement use, low B 12 concentrations and biochemically defined B 12 deficiency in US adults. Design: A cross-sectional study with adjustment for survey design. Prevalence ratios for two age groups (18―50 and >50 years) were estimated using unconditional logistic models. Outcome measures included prevalence of low serum B 12 concentration ( 10 μmol/l). Setting: A population survey of health and nutritional measures. Subjects: Subjects were non-institutionalized adults, aged 18 years and older, who participated in Phase 2 of NHANES III (Third National Health and Nutrition Examination Survey). Results: Low B 12 concentrations were less prevalent among persons consuming B 12 -containing supplements (P = 0·001) with an adjusted prevalence ratio of 0·6 (95% CI 0·3, 1·0). Biochemical B 12 deficiency showed a similar trend (P = 0·0002), with an adjusted prevalence ratio of 0·3 (95% CI 0·1, 0·8). Prevalence ratios were similar in adults >50 years of age, although the prevalence of low B 12 and biochemical deficiency was proportionally higher. Conclusions: Consumption of B 12 -containing supplements was associated with at least 50% lower prevalence of both low serum B 12 and biochemical B 12 deficiency in a nationally representative sample of US adults, suggesting increased consumption of B 12 from supplements or from fortified foods may reduce the prevalence of B 12 deficiency. Additionally, the current Recommended Daily Allowance for B 12 of 2·4 μg may be insufficient for those aged >50 years.