The effect of certain dietary factors on the apparent absorption of magnesium by the rat

Abstract

Numerous workers have established a connexion between the metabolism of magnesium and various dietary factors. Thus Colby & Frye (1951 b) working with young rats on a low-Mg, low-calcium diet observed reduction in blood Mg levels and increase in mortality rate when the casein content of the diet was increased from 24 to 50 yo. Increased intake of Ca salts or of phosphates has been reported to affect Mg metabolism in rats (Tufts & Greenberg, 1937-8; Colby & Frye, 195 I a ; Hegsted, Vitale & McGrath, 1956; O'Dell, Morris & Regan, 1960; McAleese & Forbes, 1961), guinea-pigs ,(O'Dell et al. 1960) and young dogs (Bunce, Chiemchaisri & Phillips, 1962) but no information is available from these experiments about the absorption of Mg. The results of Heller & Haddad (1936) indicate that the addition of calcium chloride to the drinking water of rats increased faecal Mg, and recently Alcock & MacIntyre (1960) found a decrease in absorption when rats receiving normal amounts of Mg and insufficient Ca had their Ca intake brought to normal. The experimental data of Malcolm (1905) are insufficient for any conclusions to be drawn concerning the effect of increased dietary Ca on Mg absorption in the dog. An increase in dietary phosphorus level reduced Mg absorption in the guinea-pig (O'Dell, Morris, Pickett & Hogan, 1957) and chick (Nugara & Edwards, 1961). Thus, although it is evident that Ca and phosphate impair Mg absorption in certain animals, the relative and combined effects of these two factors have not been studied to any great extent.