January 1997
Jeff S. Volek, William J. Kraemer, Jill A. Bush, Thomas Incledon, and Mark Boetes
Abstract
Volek, Jeff S., William J. Kraemer, Jill A. Bush, Thomas Incledon, and Mark Boetes. Testosterone and cortisol in relationship to dietary nutrients and resistance exercise.J. Appl. Physiol. 82(1): 49–54, 1997.—Manipulation of resistance exercise variables (i.e., intensity, volume, and rest periods) affects the endocrine response to exercise; however, the influence of dietary nutrients on basal and exercise-induced concentrations of hormones is less understood. The present study examined the relationship between dietary nutrients and resting and exercise-induced blood concentrations of testosterone (T) and cortisol (C). Twelve men performed a bench press exercise protocol (5 sets to failure using a 10-repetitions maximum load) and a jump squat protocol (5 sets of 10 repetitions using 30% of each subject’s 1-repetition maximum squat) with 2 min of rest between all sets. A blood sample was obtained at preexercise and 5 min postexercise for determination of serum T and C. Subjects also completed detailed dietary food records for a total of 17 days. There was a significant (P ≤ 0.05) increase in postexercise T compared with preexercise values for both the bench press (7.4%) and jump squat (15.1%) protocols; however, C was not significantly different from preexercise concentrations. Significant correlations were observed between preexercise T and percent energy protein (r = −0.71), percent energy fat (r = 0.72), saturated fatty acids (g ⋅ 1,000 kcal−1 ⋅ day−1;r = 0.77), monounsaturated fatty acids (g ⋅ 1,000 kcal−1 ⋅ day−1;r = 0.79), the polyunsaturated fat-to-saturated fat ratio (r = −0.63), and the protein-to-carbohydrate ratio (r = −0.59). There were no significant correlations observed between any nutritional variables and preexercise C or the absolute increase in T and C after exercise. These data confirm that high-intensity resistance exercise results in elevated postexercise T concentrations. A more impressive finding was that dietary nutrients may be capable of modulating resting concentrations of T.
Testosterone (T) is a steroid hormone secreted from the Leydig cells of the testes that has both anabolic and anticatabolic effects on muscle tissue (10, 22). Cortisol (C) is a steroid hormone released by the adrenal cortex that has catabolic effects on muscle tissue (10). Previous studies have demonstrated that several different resistance exercise protocols result in acute increases in serum concentrations of T and C (5, 8, 17-19, 29). The acute (exercise-induced) and chronic (resting) T and C responses to resistance exercise, although different, are determined by a complex interplay of several exercise program variables (e.g., intensity, volume, duration, rest periods, muscle mass involvement) and individual characteristics (e.g., age, health, fitness level) (6,16). Dietary intake has been rarely documented in studies examining the hormonal response to resistance exercise despite evidence indicating that specific nutrients may have the potential to alter the regulation and metabolism of T and C.
Previous studies have demonstrated that steroid hormone concentrations are subject to dietary regulation (2, 4, 24). Individuals consuming a diet containing ∼20% fat compared with a diet containing ∼40% fat (7, 9, 13, 25) have significantly lower concentrations of T. Also, replacment of dietary carbohydrate with protein has been shown to decrease T concentrations (2). These studies indicate that the energy supplied by the different macronutrients has a significant influence on T concentrations. Raben et al. (24) reported a significant decrease in resting T concentrations and an attenuation in the exercise-induced increase in T in male endurance athletes who switched from a meat-rich diet to a lacto-ovo vegetarian diet. Interestingly, both diets contained equal amounts of energy derived from protein, carbohydrate, and fat, indicating that the supply of energy from the different macronutrients was not responsible for the effect on T and that the composition of carbohydrate, protein, and fat may influence T concentrations. Thus both the amount and composition of the energy-providing macronutrients may modify T concentrations.
Few data exist regarding the relationship between nutrients and resting and exercise-induced increases in steroid hormones in young athletic men. Therefore, the primary purpose of this investigation was to examine the relationships among specific dietary nutrients and resting and resistance exercise-induced T and C concentrations.
