Explaining the variability in recommended intakes of folate, vitamin B12, iron and zinc for adults and elderly people

Objective: To signal key issues for harmonising approaches for establishing micronutrient recommendations by explaining observed variation in recommended intakes of folate, vitamin B-12, Fe and Zn for adults and elderly people. Design: We explored differences in recommended intakes of folate, vitamin B-12, Fe and Zn for adults between nine reports on micronutrient recommendations. Approaches used for setting recommendations were compared as well as eminence-based decisions regarding the selection of health indicators indicating adequacy of intakes and the consulted evidence base. Results: In nearly all reports, recommendations were based on the average nutrient requirement. Variation in recommended folate intakes (200-400 mg/d) was related to differences in the consulted evidence base, whereas variation in vitamin B-12 recommendations (1.4-3.0 mg/d) was due to the selection of different CV (10-20%) and health indicators (maintenance of haematological status or basal losses). Variation in recommended Fe intakes (men 8-10 mg/d, premenopausal women 14.8-19.6 mg/d, postmenopausal women 7.5-10.0 mg/d) was explained by different assumed reference weights and bioavailability factors (10-18%). Variation in Zn recommendations (men 7-14 mg/d, women 4.9-9.0 mg/d) was also explained by different bioavailability factors (24-48%) as well as differences in the consulted evidence base. Conclusions: For the harmonisation of approaches for setting recommended intakes of folate, vitamin B-12, Fe and Zn across European countries, standardised methods are needed to (i) select health indicators and define adequate biomarker concentrations, (ii) make assumptions about inter-individual variation in requirements, (iii) derive bioavailability factors and (iv) collate, select, interpret and integrate evidence on requirements.