Garlic supplementation increases testicular testosterone and decreases plasma corticosterone in rats fed a high protein diet

The effects of garlic supplementation on protein metabolism were investigat ed by measuring testis testosterone and plasma corticosterone in rats fed d iets with different protein levels. In Experiment 1, rats were fed experime ntal diets with different protein levels (40, 25 or 10 g/100 g casein) with or without 0.8 g/100 g garlic powder. After 28 d of feeding, testosterone contents in the testis were significantly higher and plasma corticosterone concentrations were significantly lower in rats fed 40 and 25% casein diets with garlic powder than in those fed the same diets without garlic powder. Urinary excretion of 17-ketosteroid (an index of testosterone), nitrogen b alance and hepatic arginase activity were significantly higher in rats fed the 40% casein diet with garlic powder than in the 40% casein controls. In Experiment 2, the effect of diallyldisulfide (a major volatile sulfur-conta ining compound in garlic) on the secretion of luteinizing hormone (LH) from the pituitary gland, which regulates testosterone production in the testis , was investigated in anesthetized rats. Plasma LH concentration increased dose dependently after administration of diallyldisulfide (P < 0.01, r = 0. 558). These results suggest that dietary supplementation with 0.8 g/100 g g arlic alters hormones associated with protein anabolism by increasing testi cular testosterone and decreasing plasma corticosterone in rats fed a high protein diet.