The influence of calcium on vitamin B12 absorption was investigated in two experiments. In the first we investigated whether B12 malabsorption in rats with biliary diversion through choledochocolic fistula is caused by deficiency of calcium in the small intestine. Calcium concentrations were measured in 10 fistula- and 10 sham-operated rats. Fistula rats had steatorrhea, but the concentration of calcium in the intestinal lumen was increased. In the second experiment we studied the effect of calcium deficiency on B12 absorption. Ten young rats were fed a low-calcium diet and 10 rats a control diet for 4 weeks. Rats on the low-calcium diet had moderately reduced calcium concentration in the blood and in the intestinal juice but unaltered calcium concentration in the cytosol fraction of intestinal mucosal scrapings. The absorption of 57CoB12 was unimpaired. This suggests that moderate calcium deficiency does not influence the intestinal absorption of vitamin B12 in the rat.
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