Iron supplementation in multivitamins
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Iron Content in Multivitamin Supplements: Dosage and Formulation
Most multivitamin–multimineral supplements sold online in Western and Southern Europe provide a median daily iron dose of about 14 mg, with 90% containing ferrous iron and 85% also including vitamin C (median 80 mg) to help with absorption. However, these iron and vitamin C levels are below the amounts recommended for treating or preventing iron deficiency, especially in menstruating women, where 30–60 mg of iron is advised, and for deficiency treatment, where 100 mg of iron and 500 mg of vitamin C are often recommended . In North America, standard prenatal multivitamins typically contain 27 mg of iron, which meets the Recommended Daily Allowance (RDA) but may not be enough to prevent iron deficiency as pregnancy progresses .
Iron Bioavailability and Absorption from Multivitamin Tablets
Studies show that iron in multivitamin tablets is bioavailable and can increase blood iron levels after both a single dose and daily supplementation over 28 days . The absorption of iron from prenatal multivitamin/multimineral supplements is influenced by the supplement’s formulation and whether it is taken with or without food. Taking supplements with food generally results in more reliable absorption, which is important for pregnant women who may have trouble taking supplements on an empty stomach .
Efficacy of Iron Supplementation in Multivitamins for Specific Populations
Pregnant Women
Despite meeting the RDA, many pregnant women still develop iron deficiency, especially in later pregnancy, suggesting that additional iron supplementation may be necessary for some individuals . The tolerability of prenatal multivitamins does not seem to be significantly affected by iron content (35 mg vs. 60 mg), but tablet size may influence adherence more than iron dose .
Women and Adolescent Girls (Preconception and Nonpregnant)
Daily supplementation with iron and folic acid, with or without additional vitamins, reduces the risk of anemia in women and adolescent girls before pregnancy. However, adding multivitamins to iron and folic acid does not provide a significant additional benefit for hemoglobin levels compared to iron and folic acid alone . In nonpregnant anemic women, iron-only supplements are more effective at improving hemoglobin than multivitamin–mineral supplements containing iron .
Children and Infants
In infants, multivitamin supplementation improves iron status and reduces the risk of severe anemia, while zinc supplementation can worsen iron status without increasing anemia risk . In young children with stunting and anemia, multivitamin–mineral supplementation with additional iron did not improve appetite or growth, possibly due to poor dietary diversity . For HIV-infected children with anemia, iron supplementation improves hemoglobin and immune status but may increase malaria risk in endemic areas, so malaria protection is essential when supplementing with iron .
Conclusion
Iron supplementation in multivitamins is common and can improve iron status, but the typical iron content in these products is often below the levels recommended for treating or preventing deficiency in high-risk groups. Iron in multivitamin formulations is bioavailable, but the effectiveness of supplementation depends on the population, the presence of other nutrients, and individual needs. For pregnant women and those at higher risk of deficiency, additional iron beyond standard multivitamin doses may be necessary, and supplement formulation and adherence factors should be considered for optimal outcomes.
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