Association between vitamin B-12-containing supplement consumption and prevalence of biochemically defined B-12 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 (<148pmol/l) and biochemical B-12 deficiency (serum B-12 < 148 pmol/l with concomitant homocysteine > 10 mu mol/l). Setting: A population survey of health and nutritional measures. Subjects: Subjects were non-institution 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 mu g may be insufficient for those aged >50 years.