Summary of High Protein Diets and Testosterone
- The 2022 meta-analysis found that low-carbohydrate, high-protein diets (> 3.4 g/kg/day or >1.5 grams per pound of body weight) significantly decreased men’s total testosterone levels. However, diets with protein intake below 3.4 g/kg/day or <1.5 grams per pound of body weight did not consistently affect testosterone levels.
- It is important to note that the average protein intake in the general population is around 1.3 g/kg/day, and most athletes consume protein below the 3.4 g/kg/day threshold.
High-protein diets have been popular among athletes and individuals aiming for weight loss due to their benefits, such as increased satiety, weight loss, and greater preservation of lean mass during caloric deficits. (Leidy et al., 2015) However, a recent meta-analysis has sparked discussions about the potential impact of high-protein diets on men’s testosterone levels. (Whittaker & Harris, 2022)
Defining Very High Protein Intake
Before diving into the effects of high-protein diets on testosterone, it’s crucial to understand what constitutes a high-protein diet. The term ‘high-protein’ is often used without qualification, leading to confusion. Whittaker proposes the following definitions for protein intake (Whittaker, 2023):
Very high protein (> 3.4 g/kg/day or >1.5 grams per pound of body weight),
High protein (1.9–3.4 g/kg/day or .8- 1.5 grams per pound of body weight),
Moderate protein (1.25–1.9 g/kg/day or .5 – .8 grams per pound of body weight), and
Low protein (<1.25 g/kg/day or < .5 grams per pound of body weight).
The Impact of Protein on Testosterone
Testosterone is a crucial hormone involved in various physiological processes, including muscle growth, bone density, and sexual function. (Bhasin, 1997) Understanding the relationship between high-protein diets and testosterone levels is essential for optimizing dietary recommendations and promoting overall health.
The average protein intake in conventional “high-protein” diets ranges from 1.8 to 3 g/kg/day or .8 to 1.5 grams per pound of body weight, which is below the threshold associated with decreased testosterone levels (Whittaker, 2022). Therefore, it is unlikely that the majority of individuals following high-protein diets will experience a significant decrease in testosterone levels.
The commentary discusses a recent meta-analysis that found low-carbohydrate, high-protein diets (> 3.4 g/kg of body weight/day or 1.5 grams per pound) decreased men’s total testosterone. However, diets with protein intake < 3.4 g/kg/day are not associated with a consistent decrease in testosterone. (Whittaker & Harris, 2022) This suggests that the reduction in testosterone is specifically associated with very high-protein diets (> 3.4 g/kg/day).
The Mechanism Behind the Decrease in Testosterone and High Protein Diets
Researchers don’t fully understand the exact mechanisms that cause extremely high protein diets to decrease testosterone levels. The urea cycle likely explains the testosterone decrease on very high-protein diets best. In the liver, the urea cycle removes nitrogen, a waste product of protein metabolism, from the blood and turns it into urea. The body can then safely excrete this compound in the urine.
High-protein intake can increase nitrogen levels, and the body must process and eliminate this excess nitrogen. The commentary indicates that the testosterone decrease observed on diets exceeding 3.4 g/kg/day protein might result from a hormonal response that boosts the urea cycle. This upregulation helps counteract the negative effects of hyperammonemia, a condition marked by elevated ammonia levels in the blood. Hyperammonemia might drive this response due to the systemic inflammation and oxidative stress it causes.
Such findings suggest that heightened inflammation hinders testosterone synthesis. Additionally, hypogonadism links with increased oxidative stress, which shows some improvement with treatment, indicating that oxidative stress reduces testosterone (Unluhizarci et al., 2020). Therefore, the inflammation and oxidative stress resulting from hyperammonemia might negatively affect testosterone levels.
However, the extent to which humans can upregulate the urea cycle or otherwise alter nitrogen metabolism in response to high-protein diets is currently unknown, as no studies have directly examined this.
The commentary by Joseph Whittaker provides a nuanced perspective on the relationship between high-protein intake and testosterone levels. It highlights the need for clear definitions of protein intake levels and emphasizes that only very high protein intake (> 3.4 g/kg/day) appear to decrease testosterone.
Research has demonstrated that moderate to high protein intake offer numerous benefits, such as increased satiety, weight loss, and preservation of lean mass. When assessing the potential impact of extreme protein intakes on testosterone levels, it’s crucial to think about the context and practicality. We need more research to fully grasp the mechanisms causing the decrease in androgen levels due to extremely high protein diets and to set appropriate dietary guidelines.
Bhasin, S. (1997). Testosterone Replacement Increases Fat-Free Mass and Muscle Size in Hypogonadal Men. The Journal of Clinical Endocrinology & Metabolism. https://doi.org/10.1210/jc.82.2.407
Leidy, H. J., Clifton, P. M., Astrup, A., Wycherley, T. P., Westerterp-Plantenga, M. S., Luscombe-Marsh, N. D., Woods, S. C., & Mattes, R. D. (2015). The role of protein in weight loss and maintenance. Am J Clin Nutr, 101(6), 1320s-1329s. https://doi.org/10.3945/ajcn.114.084038
Unluhizarci, K., Sık, S. K., Keti, D. B., Kose, K., Hacıoglu, A., & Karaca, Z. (2020). Treatment of male hypogonadism partially reverses oxidative stress in patients with hypogonadism. Endocr J, 67(9), 935-940. https://doi.org/10.1507/endocrj.EJ20-0133
Whittaker, J. (2023). High-protein diets and testosterone. Nutr Health, 29(2), 185-191. https://doi.org/10.1177/02601060221132922
Whittaker, J., & Harris, M. (2022). Low-carbohydrate diets and men’s cortisol and testosterone: Systematic review and meta-analysis. Nutr Health, 28(4), 543-554. https://doi.org/10.1177/02601060221083079