Meat Diets: Effect of Supplements of Calcium and Ferrous Carbonates on Rats Fed Meat

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Abstract
Young male rats were fed a diet of raw minced beef, containing 17% of fat and with adequate supplements of vitamins A and D. Growth ceased after a few weeks, with indications of severe calcium deficiency. The bones were undersized, had thin walls and a low ash content, and were often fractured. The skeletal muscles were underdeveloped and fat depots were virtually absent. The liver and testes, however, were only slightly below normal in size, and hence represented abnormally high percentages of the total body weight. With either adequate (0.5%) or excessive (5.0%) amounts of calcium carbonate added to the meat the rats remained outwardly in good general health, grew well, and had normal bones and body conformation. Growth was slightly less rapid, however, with the excessive than with the adequate addition of calcium carbonate. Rats given meat with either no calcium carbonate or an excess, without supplements of iron, became anemic. Another sign of defective iron metabolism was loss of pigment from the incisor teeth. In contrast, rats given the adequate allowance of calcium carbonate had almost normal blood, and less severe dental depigmentation. Liberal additions of ferrous carbonate (2.5%) to the meat had no effect on the growth or skeletal development of the rats when the diet also contained calcium carbonate, at either the adequate or excessive level. When the diet contained no calcium carbonate, the growth rate, the maximal body weights attained, and the ash contents of the bones were further reduced by the addition to the meat of ferrous carbonate. No signs of iron deficiency, whether looked for in the blood or teeth, were seen in those rats given ferrous carbonate, irrespective of the calcium intake. Even undersized and feeble rats, suffering from severe calcium deficiency, were not anemic, and had normally colored teeth, provided they were given ferrous carbonate. In histological studies no stainable iron was found in either the spleens or livers of rats not given iron. In the rats given ferrous carbonate, stainable iron was invariably found in the spleen, in about equal intensity in each group. In the liver, iron staining was inversely related to the calcium intake, being intense with no supplement of calcium carbonate, moderate with 0.5%, and absent with 5.0%. Chemical estimations of iron in the livers of the rats, indicated concentrations that were directly related to the iron intake and inversely related to the calcium intake. These observations confirm and amplify earlier claims that the metabolism of calcium and iron are interrelated. This interrelationship, which is probably nonspecific, is presumably typical of many similar interrelationships in mineral metabolism.