High protein diets decrease testosterone by 37%

A new study conducted at the University of Worcester and published in the academic journal: Nutrition and Health, has found high protein diets decrease men’s testosterone by 37%.

For the average man, this would cause medically low testosterone (hypogonadism), substantially increasing the risk of infertility, low sperm counts, and erectile dysfunction. Low testosterone levels are linked to a higher risk of chronic diseases such as heart disease, diabetes, and Alzheimer’s. Moreover, healthy testosterone levels are vitally important for strength, muscle building, and athletic performance.

This finding was part of a large study, which complied the results of 27 studies, with a total of 309 men. The research also found low-carbohydrate diets, especially high protein ones, increase the hormone cortisol. This is commonly known as the body’s stress hormone, and is released during the ‘fight or flight’ response. High levels of cortisol suppress the immune system, making people more susceptible to catching viral and bacterial infections such as colds, flus, and Covid-19.

High protein diets can induce a phenomenon known as ‘rabbit starvation’. This was first discovered by the Romans, when soldiers were forced to survive on large quantities of rabbits (i.e. lean meat), during the siege of Villanueva del Campo, many of which developed severe diarrhoea and died. In the body, protein breaks down into ammonia, which at high levels becomes toxic. This results in a number of adverse effects including diarrhoea, nausea, and ultimately death. This new research indicates low testosterone is another symptom of rabbit starvation, also known as protein poising.

Joseph Whittaker the lead researcher said “Most people eat about 17% protein, and the high protein diets which caused low testosterone were all above 35%, which is very high. So for the average person, there is nothing to worry about, however for people on high protein diets, they should limit protein to no more than 25%.”

Bodybuilders, weight lifters, and those on extreme weight loss diets are most at risk of excessive protein intakes. Typically, this is achieved by eating lot of lean meats, white fish, and protein shakes. People have a natural aversion to consuming large quantities of lean meat, for this very reason. It is the body’s way of warning us against very high protein intakes.

The finding that low carbohydrates diets increase cortisol is very interesting, as these diets have become incredibly popular over recent years, with many celebrities such as Kim Kardashian, LeBron James, and Meagan Fox, promoting them. However, the researchers stress further work needs to be done in this area, to know if this is necessarily bad.

For the published article please Whittaker, the lead researcher is available for interview and/or further comment.