ObjectivesThe authors investigated whether low vitamin B12intake, impaired gastric function,Helicobacter pyloriinfection, and bacterial overgrowth were risk factors for the high prevalence of cobalamin deficiency observed in Guatemalan children.MethodsThe plasma cobalamin concentration of 556 school children was measured and classified as low, marginal, or adequate. In 60 children from each of these three groups, concentrations of serum methylmalonic acid (MMA), plasma homocysteine, and plasma holotranscobalamin II were measured, and usual dietary B12intake was estimated. Serum gastrin and pepsinogen I concentrations were measured, andH. pyloriand bacterial overgrowth were diagnosed using13C-urea and13C-xylose breath tests, respectively.ResultsH. pyloriinfection was present in 83% (144 of 174) of children, and bacterial overgrowth was found in 25% (28 of 113). Children withH. pyloriinfection had higher serum gastrin and pepsinogen I. There were no significant differences among the plasma cobalamin groups in the prevalence ofH. pyloriinfection, bacterial overgrowth, serum gastrin, or pepsinogen I concentrations. However, there was a significant positive correlation between serum MMA and gastrin concentrations. The average daily consumption of dietary B12was 5.5 ± 5.2 &mgr;g/day, but intakes for 23% of children were <1.8 &mgr;g/day. B12intake from fortified snacks added an additional 0.3 ± 0.2 &mgr;g/day. B12intake was not significantly different among the plasma cobalamin groups, but it was significantly correlated with plasma cobalamin.ConclusionsThe specific cause of cobalamin deficiency in this population remains unclear, but these results suggest that low dietary B12intake is a risk factor and alterations in gastric secretions may also play a role.