Effect of Several Calcium Salts on the Utilization of Lactose

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Abstract
Rats were fed an adequate ration containing 60% lactose, plus 1.0 or 0.5% of calcium added in the form of six different calcium salts, respectively, tricalcium phosphate, carbonate, citrate, lactate, levulinate and gluconate. With the phosphate, carbonate, citrate and levulinate rats showed as good growth, less diarrhea in general, the same degree of galactemia and a similar incidence of cataract as on the plain 60% lactose ration. Calcium lactate was somewhat toxic at the higher level but at the lower level results were more nearly comparable to those with the other calcium salts mentioned above. Calcium gluconate fed at the 1.0% calcium level resulted in poor survival, loss of weight, severe diarrhea and low normal blood sugar. At the 0.5% level of calcium survival was better, but growth was poor, diarrhea moderate to severe, blood sugar a low normal and lenticular changes few if any. Calcium gluconate exerted no apparent inhibitory effect upon the absorption or utilization of starch, dextrin, sucrose, glucose or galactose. Sodium gluconate exerted a deleterious effect similar to but more severe than calcium gluconate when fed in a lactose ration. These criteria indicate that the gluconate radical may interefere with lactase activity in the intestinal tract. The phenomenon of ‘competitive inhibition’ in enzyme action is postulated as a possible explanation of these findings.