Effect of genetic and dietary obesity on sodium, potassium, calcium and magnesium handling by the rat

Abstract

The balances and content of the most abundant minerals (sodium, potassium, calcium and magnesium) in the body of Wistar, Zucker lean and Zucker obese rats fed a reference or cafeteria diet from days 30 to 60 after birth have been studied. Obese rats ingested more sodium when available, and retained it more than lean rats. Absorption of minerals was inversely correlated with their abundance in the diet and the amount of food consumed, and was affected by consumption of the cafeteria diet, which was poorer in minerals than the reference. Urinary excretion was maximal under conditions of highest internal availability for sodium, potassium and calcium, but was not affected by magnesium content of the diet. The accumulation in the body of the elements studied was more uniform when related to the amount of the element contained in the body. Genetic obesity showed a distinct pattern of management of minerals to cafeteria-diet-induced overweight, since the effects of diet on mineral content were less immediate than the differences due to strain or genetic obesity. In general, there were only slight differences due to strain in animals subjected to the same diet, and even more homogeneous data for all animals when provision for the diluting effect of fat on body mass was taken into account. It is concluded that the cafeteria diet is not deficient in potassium, calcium or magnesium, since the rat adapts its absorbing and retaining strategies to match the dietary availability of these minerals. The excess dietary sodium is excreted in the urine.