Dietary minerals modify the food intake suppressing effects of high casein diets fed to rats

Abstract

Food intake, growth, and urinary urea and ammonia excretion were studied in young rats undergoing adaptation to high protein diets (70% casein) containing varying amounts of potassium, sodium and chloride. Two commercial mineral mixtures were used. The Bernhart-Tomarelli (BT) mineral mixture is low in K, Na and Cl compared to the TD (modified Williams-Briggs) mineral mixture. Rats consumed significantly less food and had poor growth when fed 70% casein diets containing the BT mineral mixture. Food intake and feed efficiency improved significantly when the BT diets were supplemented with KCl and NaCl, Na acetate or K acetate but not 3-chloropropionate. Urinary urea and ammonia excretion were directly proportional to food (protein) intake. However, body weight gain during the last 3 days of the 9-day study (experiment 3) was negatively correlated with urinary ammonia nitrogen (milligrams per gram food eaten) but not with urinary urea nitrogen. It is concluded that dietary K and/or Na content affects food consumption in rats fed high casein diets. Alterations in renal capacity for handling ammonia may be responsible for the food intake enhancing effect of K or Na in rats fed a high casein diet.