Supplementary Material for: Systematic Review on Daily Vitamin B12 Losses and Bioavailability for Deriving Recommendations on Vitamin B12 Intake with the Factorial Approach

<b><i>Aims:</i></b> To systematically review the literature on daily losses and bioavailability of vitamin B12. These estimates could be used for deriving recommendations on vitamin B12 intake for adults and elderly. <b><i>Methods:</i></b> We identified publications on daily vitamin B12 losses (July 2011) and publications on the bioavailability of vitamin B12 from foods or diets (June 2010) in MEDLINE, EMBASE and the Cochrane Library. <b><i>Results:</i></b> A pooled analysis of five studies (52 subjects) showed that 0.13 ± 0.03% of the total body store is lost per day. Absorption of vitamin B12 ranged from 4.5 (dose of 38 µg from consumption of liver) to 83% (dose of 3.0 µg from consumption of mutton meat). Data from eight studies including 83 subjects suggested that the amount of vitamin B12 absorbed from food (A_i) increased with increasing doses of vitamin B12 (D_i) as described by the equation: ln(A_i) = 0.7694 * ln(D_i) - 0.9614. <b><i>Conclusion:</i></b> Daily vitamin B12 losses in apparently healthy adults and elderly probably range from 1.4 to 5.1 µg. Vitamin B12 intakes needed to compensate for these losses seem to range from 3.8 to 20.7 µg. More evidence is needed on the relationships between biochemical markers of vitamin B12 status, vitamin B12 body store and long-term health outcomes to evaluate whether current recommendations on vitamin B12 intake (1.4-3 µg) need to be changed.

**研究目的**：系统综述维生素B12每日丢失量及生物利用度（bioavailability）的相关研究文献，所得估算结果可用于制定成人及老年人的维生素B12摄入推荐标准。
**研究方法**：本研究在MEDLINE、EMBASE及Cochrane图书馆中，检索了截至2011年7月的维生素B12每日丢失量相关文献，以及截至2010年6月的食物或膳食来源维生素B12生物利用度相关文献。
**研究结果**：对5项共纳入52名受试者的研究进行合并分析（pooled analysis）后显示，人体每日总维生素B12体内储存量的丢失比例为0.13±0.03%。维生素B12的吸收率范围为4.5%（通过食用肝脏摄入38μg剂量时）至83%（通过食用羊肉摄入3.0μg剂量时）。针对8项共纳入83名受试者的研究数据进行分析后发现，从食物中吸收的维生素B12量（A_i）随摄入的维生素B12剂量（D_i）增加而升高，二者符合如下关系式：ln(A_i) = 0.7694 × ln(D_i) - 0.9614。
**研究结论**：外观健康的成人及老年人每日维生素B12丢失量介于1.4~5.1μg之间，用于补偿该丢失量所需的维生素B12摄入量范围为3.8~20.7μg。目前尚需更多研究证据，以明确维生素B12营养状态的生化标志物、体内维生素B12储存量与长期健康结局之间的关联，从而评估当前维生素B12摄入推荐量（1.4~3μg）是否需要调整。