Geophagy, iron status and anaemia among primary school children in Western Kenya

As part of a cross-sectional study among 156 primary school children (median age 13 years, range 10-18) in Western Kenya, geophagy was assessed through interviews. 114 (73.1%) of these children reported eating soil daily. Haemoglobin levels were determined in all 156 children and serum ferritin concentrations in 135. The mean haemoglobin (Hb) concentration was 12.7 g/dl, and median ferritin concentration 27.2 microg/l. Both the proportion of anaemic (Hb < 11.0 g/dl) and of iron-depleted (ferritin < 12 microg/l) children was significantly higher among the geophageous children than among the nongeophageous (9.6% vs. 0% anaemia; P = 0.037; 18.4% vs. 5.4% iron depletion; P = 0.046). Serum ferritin and haemoglobin concentrations were not correlated (r = 0. 13 5; P = 0. 100). Multiple regression analysis showed that geophagy, hookworm eggs per gram faeces and malaria parasite counts per microl blood were independent predictors of serum ferritin, when controlling for other helminth infections, age and sex, and socio-economic and educational background of the children's families and family size (y = 36.038-11.247(geophagy) -- 0.010(hookworm epg) + 0.001(malaria parasite counts); R2 = 0.17). Multiple regression analysis with haemoglobin as dependent variable and the same independent variables did not reveal any significant predictors. Analysis of the soil eaten by the children revealed a mean HCl-extractable iron content of 168.9 mg/kg (SD 44.9). Based on the data on the amounts eaten daily and this mean iron content, soil could provide on average 4.7 mg iron to a geophageous child (interquartile range 2.1-7.1 mg), which is equivalent to 32% of the Recommended Nutrient Intake (RNI) for girls (interquartile range 14-48%) or 42% of the RNI for boys (interquartile range 19-63%). Iron depletion and anaemia are associated with geophagy, but only serum ferritin concentrations were shown to be dependent upon geophagy in the regression model. From the cross-sectional data no inference about causality can be made. To clarify the possible causal relationships involved, longitudinal studies and iron-supplementation intervention studies are needed.