Approximately one out of three non-pregnant women of reproductive age are anaemic worldwide. Although causes of anaemia are multiple, it very often results from sustained iron deficiency. Being anaemic makes women more likely to suffer infections and to have a diminished physical and work performance. If they become pregnant, they may also have a greater risk of having low birth weight babies and other complications during delivery.
Daily iron supplementation (sometimes combined with folic acid and other vitamins and minerals) for three months has traditionally been the standard practice to prevent or treat anaemia in women, but its use has been limited as it is frequently associated with side effects such as nausea, teeth staining or constipation. Intermittent supplementation (that is the consumption of supplements one, two or three times a week on non-consecutive days) has been proposed as an effective and safer alternative to daily supplementation. It has been suggested that intermittent regimens increase haemoglobin concentrations with fewer negative side effects and this may encourage women to adhere better to the intervention for a longer period. In this review we included studies examining the administration of intermittent iron supplements versus no intervention, a placebo or the same supplements given on a daily basis.
This review includes 21 randomised controlled trials involving 10,258 women. Although the quality across trials was variable, the findings suggest that women receiving intermittent supplementation with iron alone or in combination with folic acid or other nutrients were less likely to be anaemic and had higher haemoglobin and ferritin concentrations than those women who received no iron supplements or a placebo. However, intermittent supplementation was less effective than daily supplementation in preventing or controlling anaemia. Information on disease outcomes, adherence, side effects, economic productivity and work performance is scarce and the evidence about the effects of intermittent supplementation on them is unclear.
Overall, whether the supplements were given once or twice weekly, for less or more than three months, contained less or more than 60 mg of elemental iron per week, or to populations with different degrees of anaemia at baseline did not seem to affect the findings. Furthermore, the response did not differ in areas where malaria is frequent, although very few trials were conducted in these settings.