Dietary Minerals Modify the Food Intake Suppressing Effects of High Casein Diets Fed to Rats

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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.