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

Abstract

Objective To signal key issues for harmonising approaches for establishing micronutrient recommendations by explaining observed variation in recommended intakes of folate, vitamin B12, Fe and Zn for adults and elderly people. Design We explored differences in recommended intakes of folate, vitamin B12, 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 µg/d) was related to differences in the consulted evidence base, whereas variation in vitamin B12 recommendations (1·4–3·0 µg/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 B12, 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