Calcium absorption.

Abstract

If a definite amount of an unabsorbable compound, such as ferric oxide, be mixed with a diet and the feces be analyzed for iron and for any food constituent, such as calcium, it is possible to determine the percentage absorption or “utilization” of the latter without an accurate separation of the feces. If the ratio of calcium to iron in the food be 10:1 and in the feces 5:1, calcium unabsorbed amounts to 50 per cent and calcium abserbed would of course also be 50 per cent.

Using this method, it has been shown that lactose in contrast with other common sugars, markedly increases the absorption of calcium. Lower fatty acids have a more favorable effect than higher fatty acids. Antirachitic substance produces the expected result.

In the same way, if animals fed an iron containing diet are killed at the height of digestion and analyses made of the intestinal contents at different levels, the percentage absorption of food products in different parts of the intestines may be estimated.

Experiments of this type on rachitic albino rats on diets with or without cod liver oil give interesting results. Using a calciumhigh phosphorus-low diet rats with or without cod liver oil show considerable calcium absorption in the upper small intestine. This type of rickets is not due, therefore, to a failure of calcium absorption. Excretion of absorbed calcium into the lower bowel does, however, bring about a negative or subnormal calcium balance.

Phosphorus, on the other hand, is actually excreted into the upper intestines. Animals given cod liver oil make up for this loss by absorption from the cecum and large intestines. Rachitic animals do not and, therefore, the phosphorus balance remains negative.

On a milk diet, high in both calcium and phosphorus, both are absorbed to a considerable degree in the small intestine.