Effect of dietary protein on post-prandial salivary cortisol and androgen levels in healthy women volunteers
Al-Dujaili, Emad A. S.
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Lyles, A. & Al-Dujaili, E. (2009) Effect of dietary protein on post-prandial salivary cortisol and androgen levels in healthy women volunteers, , , , pp. P3,
Objective: Macronutrients such as protein and fat have been postulated to elicit post-prandial effects upon cortisol and testosterone concentrations. This pilot study was conducted to test the hypothesis that a meal high in protein content can elicit a positive effect on post-prandial cortisol levels whilst producing a negative effect on DHEA and testosterone levels. Methods: In 13 healthy female volunteers (aged between 19-29 years; BMI ranged from 19.3 to 24.7 kg/m2), salivary cortisol, DHEA and testosterone were measured in saliva samples taken before and after two meals, one of high protein content (65% energy as protein); and the other of low protein content (12% energy as protein) in a randomised crossover design. Saliva samples from each participant at regular intervals on the day of intervention were collected (09.00 a.m. till 17.00 p.m). Steroid hormone concentrations were measured using specific and sensitive ELISA methods. Measures of mood, appetite and psychological well-being were also recorded. Results: An acute and significant meal-dependent increase in salivary cortisol was detected at approximately 90 mins post-prandially which was dependent upon the proportion of protein in the meal (P=0.05 in absolute cortisol levels and P=0.04 in the difference at 90 min and 150 min versus premeal value). In addition, midday meal rich in protein appears to affect the latency of the post-prandial cortisol peak. No significant difference was elicited in DHEA levels following the two midday meals, but there was a trend increase following the low protein meal and a decrease in the high protein meal (P=0.06). No overall difference in testosterone levels, however a significant decrease between waking and 2 h post ingestion of low protein meal only was found (P=0.01). Conclusion: This investigation suggests a role for macronutrients such as protein in influencing the transient daily steroid hormone levels and their subsequent implications with metabolic homeostasis and hormone-dependent disease.