A study of low-nutrient diets used for aging studies in the rat

The effects of diets of low caloric value on rats used in aging studies were investigated. Groups of 85 Sprague-Dawley rats were fed ad libitum from 3 months of age on three different diets containing 8 or 10 Megajoule (MJ) of metabolizable energy and 80 or 100 g of crude protein/kg. Body weights, food consumption, and morphological and biochemical parameters were monitored throughout life. Kidneys were examined histologically. Rats given the diet with highest energy and protein ate less food, attained greater weights, and had larger abdominal fat deposits than those on the lower energy diets. They had a raised proteinuria, and nearly half developed glomerulosclerosis and tubulo-interstitial damage by 26 months. There was no significant difference in mortality between the groups, and no other serious abnormalities were observed. It is concluded that rats can be maintained into old age with no signs of nutritional inadequacy on diets with lower energy and protein contents than those in general use.