This new overview of reviews summarised the evidence from systematic reviews regarding the benefits or harms of nutrition-specific interventions for preventing and controlling anaemia in anaemic or non-anaemic, apparently healthy populations throughout the life cycle.
The review included 75 systematic reviews. Of these, 33 provided GRADE assessments, which varied between high and very low. The primary outcomes were haemoglobin (Hb) concentration, anaemia, and iron deficiency anaemia (IDA); secondary outcomes were iron deficiency (ID), severe anaemia and adverse effects (e.g. diarrhoea, vomiting).
The results were as follows.
Infants (6 to 23 months)
- Iron supplementation increased haemoglobin (Hb) levels and reduced the risk of anaemia and iron deficiency anaemia (IDA) compared with placebo, no intervention, or other interventions (two reviews).
- Iron fortification of milk or cereals, multiple-micronutrient powder (MMNP), home fortification of complementary foods and supplementary feeding increased Hb levels and reduced the risk of anaemia (six reviews).
- Lipid-based nutrient supplementation (LNS) reduced the risk of anaemia (one review).
- Caterpillar cereal increased Hb levels and IDA prevalence (one review).
- Food-based strategies (red meat and fortified cow's milk, beef) showed no evidence of a difference between groups (one review).
Preschool and school-aged children (2 to 10 years)
- Daily or intermittent (e.g. 1 to 3 times per week) iron supplementation increased Hb levels and reduced the risk of anaemia and ID (two reviews).
- For daily versus intermittent iron supplementation, there was no difference in Hb levels, but an increased risk of anaemia and ID for the intermittent regime (one review).
- Hb levels were higher and there was a reduced risk of anaemia and ID for:
- zinc plus iron supplementation versus zinc alone (one review);
- multiple-micronutrient (MMN)-fortified beverages (one review); and
- point-of-use fortification of food with iron-containing micronutrient powder (MNP) (one review).
Adolescent children (11 to 18 years)
- Hb levels were higher and there was a reduced risk of anaemia for:
- intermittent iron supplementation alone or in c ombination with other micronutrients;
- iron supplementation with or without folic acid supplementation;
- other micronutrient supplementation (three reviews for prevention or treatment).
- Nutritional supplementation and counselling reduced IDA (one review).
- Iron supplementation with or without folic acid appeared to increase Hb levels but have no effect on the incidence of anaemia (one review for prevention).
Non-pregnant women of reproductive age (19 to 49 years)
- Iron therapy (oral, intravenous, intramuscular) increased Hb levels (two reviews).
- Intravenous iron increased Hb levels compared with oral iron (one review).
- Daily iron supplementation with or without folic acid or vitamin C increased Hb levels and reduced the risk of anaemia and ID (one review).
Pregnant women of reproductive age (15 to 49 years)
- Daily iron supplementation with or without folic acid increased Hb levels in the third trimester or at delivery, and in the postpartum period, and reduced the risk of anaemia, IDA and ID in the third trimester or at delivery (one review).
- Intravenous iron versus oral iron or intramuscular iron increased Hb levels (six reviews).
- Vitamin A supplementation alone versus placebo, no intervention or other micronutrient increased Hb levels and reduced the risk of anaemia for the mother (one review).
- Supplementation with oral bovine lactoferrin versus oral ferrous iron preparations increased Hb levels and reduced gastrointestinal side effects (one review).
- Compared to iron or folic acid and MMNs, LNS increased the risk of anaemia (one review).
Mixed population (all ages)
- Iron supplementation versus placebo or control increased Hb levels in healthy children, adults, and elderly people (four reviews).
- MMN fortification versus placebo or no treatment increased Hb levels in children, as did iron supplementation, but Hb levels decreased for those receiving dietary interventions (two reviews).
- Intravenous iron resulted in higher Hb levels than oral iron (one review).
- Vitamin B12 or folic acid supplementation did not increase Hb levels (one review).
- Iron fortification of food, iron-fortified soy sauce, double-fortified salt with iron and iodine, and fortified condiments or noodles increased Hb levels and reduced the risk of anaemia (eight reviews).
- Foods prepared in iron pots showed the potential to increase Hb levels in children (one review).
No review focused on older adult women (50 to 65 years plus) or men (19 to 65 years plus), and anaemia and malaria prevalence were rarely reported.
The evidence is current to August 2020.
The review authors concluded that, compared to no treatment, daily iron supplementation may increase Hb levels and reduce the risk of anaemia and IDA in infants, preschool and school-aged children, and pregnant and non-pregnant women. Iron fortification of foods in infants and use of iron pots with children may have prophylactic benefits for malaria endemicity low-risk populations. In any age group, only a limited number of reviews assessed interventions to improve dietary diversity and quality. Future trials should assess the effects of these types of interventions and consider the requirements of different populations.
Read the full review here on the Cochrane Library.