Failure of twice-weekly iron supplementation to increase blood haemoglobin and serum ferritin concentrations: results of a randomized controlled trial

Abstract

In order to increase the intestinal absorption of iron whilst simultaneously minimising the side-effects and thus increasing compliance, once- or twice-weekly, instead of daily, iron supplementation has been widely recommended. In a randomized, placebo-controlled, double-blind study in western Kenya, a tablet of ferrous dextran (containing 60 mg elemental iron) or an identical-looking placebo tablet was provided twice-weekly for 12 months to each child or adult investigated. At baseline each subject had a moderately low blood concentration of haemoglobin (Hb). Initial Hb and serum ferritin (SF) concentrations were determined and each subject was tested for malarial and helminth infection and treated, if necessary, with the appropriate anthelminthic drug(s). Overall, 200 children (aged 4-15 years) and 129 adults (aged 16-63 years) completed the 12-month study. At baseline, 47.5% of the children and 58.1% of the adults were anaemic, hookworm (detected in 60.0% of the children and 69.9% of the adults) was the most common helminth infection, and malaria was endemic. The results of bivariate analyses indicated that twice-weekly iron supplementation had no significant effect on blood Hb or SF concentrations, either in the children or the adults investigated. The results were confirmed in multiple linear-regression analyses, which revealed that the predictors of the final Hb concentration in the children investigated were age and infection, after enrollment, with Ascaris lumbricoides. Gender and the serum concentration of alpha-1-antichymotrypsin (ACT) at final follow-up were predictors of the final SF concentration in the children. In adults, the predictors of the final Hb concentration were gender and HIV infection, and the predictors of the final SF concentration were age and the serum concentration of ACT at the final follow-up. Twice-weekly iron supplementation did not increase Hb or iron stores in children or adults. Since compliance appeared to be high, this lack of effect may be the result of an inadequate dose of iron or of subjects who have deficiencies in micronutrients other than iron.