Nephrocalcinosis and diets containing alkali- and non-alkali-treated soy protein.

Diets containing alkali-treated soy protein have been shown to cause nephrocalcinosis in rats. In order to determine if alkali-treated soy protein is the dietary component that induces nephrocalcinosis, the effects of a purified diet containing 20% alpha-protein (an alkali-treated soy protein) were compared with the effects of the same diet containing 20% promine-D (a non-alkali-treated soy protein) on renal morphology and renal calcium and phosphorus metabolism. After a 9-week feeding trial, light and transmission electron microscopy revealed that the animals fed either the alpha-protein or promine-D diet developed nephrocalcinosis. In fact, the type of nephrocalcinosis was the same in both groups of animals. Moreover, quantitative determinations of total renal calcium and phosphorus showed that the severity of nephrocalcinosis was also the same in the two groups. No signs of nephrocalcinosis were detected in rats fed a standard commercial laboratory diet. Since nephrocalcinosis was present in the animals fed the promine-D diet, and that it was identical to that found in the animals fed the alpha-protein diet, it appears that alkali-treated soy protein is not the factor responsible for nephrocalcinosis in rats fed a diet containing the protein.