Diet-induced alterations of hGH secretion in man

Studies were designed to determine whether variations in diet composition could modify the secretion of human growth hormone. Eight men and seven women ingested experimental diets for 10-12 days. Each experimental diet was preceded by a control diet for five days. Experimental diets studied in men were a) 2300 calorie, 80% carbohydrate (8 men); b) 2300 calorie, 75% high-fat (7 men); c) 2300 calorie, 70% high-protein (5 men); d) 3600 calorie, "control" (40% carbohydrate, 40% fat, 20% protein) (5 men); and e) 3600 calorie, 80% high-carbohydrate (5 men). A control diet and a high-carbohydrate (5 men). A control diet and a high-carbohydrate diet at the 2300 calorie level were studied in women. Each diet study was terminated by a 72 hour fast. Serum samples were collected hourly for 24 hours after each control period, on the eigth, ninth, or tenth day of each study, and during the final day of each fast. High-carbohydrate diets at the 2300 calorie level caused a significant decrease of growth hormone values in serum in each of eight men (sign test of significance, P less than .01). The mean figures were likewise significantly decreased. Isocaloric diets of high fat and high protein did not alter growth hormone concentrations in serum. A high-caloric diet similar to the control diet in composition was without effect on growth hormone secretion in men; however, a high-carbohydrate diet at the higher caloric level again depressed growth hormone values in plasma. On the third day of a 72 hour fast, growth hormone values in serum increased 287% in men, from a mean control serum concentration of 4.4 +/- 0.8 ng/ml to 11.9 +/- 5.0 ng/ml (P less than .01). Women, unlike men, had no significant decrease in growth hormone concentrations in serum over a 24 hour period after the high-carbohydrate diet, and the increase after starvation was significantly less than that in men, achieving significance only when evaluated by paired analysis. Growth hormone values in serum after the infusion of arginine followed a similar pattern, i.e., decreased after high carbohydrate but unaffected by other diets in men; high carbohydrate diets did not alter the growth hormone response of women to arginine.