Men who eat high-protein diets are being warned they could affect their fertility after research found they could lead to a sharp drop in testosterone. One study found that men who ate large amounts of lean meat, white fish and protein shakes could see their testosterone levels drop by up to 37%.
Diets are often favored by bodybuilders, weightlifters, and those aiming for extreme weight loss. They are often seen as a way to increase muscle mass and aid in weight loss.
However, research by the University of Worcester has found that not only can eating too many of these foods affect fertility, but could also put people at higher risk for chronic diseases as well as contracting infections, including covid- 19.
The results, published in the academic journal Nutrition and Health, mean that this reduced level of testosterone for the average man would lead to medically low testosterone (hypogonadism), significantly increasing the risk of infertility, low sperm count and erectile dysfunction.
Low testosterone levels are linked to a higher risk of chronic diseases such as heart disease, diabetes and Alzheimer’s disease. Additionally, healthy testosterone levels are vitally important for strength, muscle building, and athletic performance.
The findings came after researchers compiled the results of 27 studies, involving a total of 309 men. Research has also found that low carb diets, especially those high in protein, increase the hormone cortisol.
This is commonly referred to as the body’s stress hormone, and it 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, flu 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 diarrhea and died.
In the body, proteins break down into ammonia, which at high levels becomes toxic. This leads to a number of adverse effects, including diarrhea, nausea, and ultimately death. This new research indicates that low testosterone is another symptom of rabbit starvation, also known as protein balance.
Joseph Whittaker, the lead researcher, said: “Most people eat about 17% protein, and the high protein diets that caused low testosterone were all above 35%, which is very high. So for the average person, there is nothing to worry about, but for people on a high protein diet, they should limit protein to no more than 25%.
People have a natural aversion to consuming large amounts of lean meat for this very reason. This is the body’s way of warning us against very high protein intake.
The researchers said it was interesting to see that low-carb diets increase cortisol, as these diets have become incredibly popular in recent years, with many celebrities such as Kim Kardashian, LeBron James and Meagan Fox, who promote it. However, they point out that more work needs to be done in this area, to find out if this is necessarily bad.
For the published article, please see: https://journals.sagepub.com/doi/10.1177/02601060221083079
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