11 Mar Links Between Diet and Men’s Testosterone Levels
MedicalResearch.com Interview with:
Joe Whittaker, MSc
Joe Whittaker, MSc
Nutritionist
MedicalResearch.com: What is the background for this study?
Response: There are several studies showing a generational decline in men’s testosterone levels, beginning in the 1970s. This is due to a variety of factors such as poorer diets, lack of physical activity, and increasing toxin exposure. Therefore, there is intense research interest in ways we can optimise testosterone levels, to combat this generational decline.
Some well-known studies have found low-carbohydrate diets boost testosterone levels, but others have show the reverse effect. So, to settle the controversy we gathered and reanalysed all known studies on the topic. There was also the question of high protein diets and their effects on testosterone, which are currently disputed.
MedicalResearch.com: What are the main findings?
Response: We found that whilst low carbohydrate diets had no effect on testosterone, high protein diets caused a large decrease in testosterone (approximately 37%). This is very significant, as such a large decrease would give the average man medically low testosterone (hypogonadism). We also found on low-carbohydrates diets increased the stress hormone cortisol, particularly after exercise. Cortisol is known to supress the immune system, so this effect could be detrimental.
MedicalResearch.com: What should readers take away from your report?
Response: Very high protein diets have been shown to have many adverse effects, and our study adds low testosterone to this list. However, the detrimental effects are generally only seen at protein intakes above 35%. The average person eats 15-20% protein, so they have nothing to worry about. People most at risk of excessive protein intakes are bodybuilders, weight lifters, and those on extreme weight loss diets. These people should limit protein to no more than 25% of their daily calories. The finding that low-carbohydrate diets increase cortisol, suggests they supress the immune system, particularly after exercise. So for athletes and others who exercise a lot, they may need to reconsider using low-carbohydrates diets, particularly if they frequently have colds, flus, and other viral infections.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: I would like to see more research into the effects of actual foods on testosterone (i.e. meat, fish, fruit, vegetables, dairy), rather than different diets (i.e. low carb, low fat). Some of the studies showing low-carbohydrate diets boost testosterone, may be because they include a lot of nutrient rich foods, such as meat, fish, cheese, and vegetables; whilst the conflicting studies that show low-carbohydrate diets decrease testosterone, may be due to using a more processed version of the diet, heavily relying on low-carb snack foods and other processed foods.
MedicalResearch.com: Is there anything else you would like to add?
Response: There were no conflicts of interest in this study. I believe we gave a fair assessment of the evidence. I run a private nutrition clinic, where I specialise in maximising testosterone through diet and exercise, so if readers want more guidance please visit my website: https://joewhittakernutrition.com
Citation:
Whittaker J, Harris M. Low-carbohydrate diets and men’s cortisol and testosterone: Systematic review and meta-analysis. Nutr Health. 2022 Mar 7:2601060221083079. doi: 10.1177/02601060221083079. Epub ahead of print. PMID: 35254136.
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