Folic acid malabsorption in atrophic gastritis: Possible compensation by bacterial folate synthesis

Abstract

Folic acid absorption was studied in 12 elderly subjects with atrophic gastritis and 10 elderly normal controls using tritium-labeled pteroylmonoglutamic acid. Two folic acid absorption tests were carried out on each subject with 120 ml of either water or 0.1 N HC1. Folic acid absorption was significantly lower in subjects with atrophic gastritis than in normal controls (31% vs. 51%, respectively; p < 0.01). In subjects with atrophic gastritis, folic acid absorption rose significantly to 54% (p < 0.001) when administered with acid, but did not change in normal controls (50%). Serum folate levels were normal in all subjects. Proximal small intestinal pH was higher in atrophic gastritis subjects than in normal controls (7.1 vs. 6.7, respectively; p < 0.05), as were bacterial counts of small intestinal fluid (p < 0.01). Bacteria cultured from the aspirates of subjects with atrophic gastritis were able to synthesize folate in vitro when incubated in a folate-free medium. Atrophic gastritis results in folic acid malabsorption but not in folate deficiency, possibly due to increased bacterial synthesis of folate in the small intestine.