Is a High-Protein Diet Destroying Your Testosterone Levels?

Male stereotypes tend to suggest that the most manly diets are those rich in protein. Manly men love meat, they enjoy eating raw eggs a la Gaston de Beauty and the Beast and fuel up with protein shakes before hitting the gym to pump up some iron. Contrary to these high-protein images of masculinity, however, some recent research suggests that a high-protein diet may actually lower testosterone levels in men.

The study, published in the journal Nutrition and health and led by researcher Joe Whittaker of the University of Worcester in England, tested the testosterone levels of 309 men over the course of eight weeks. Subjects were fed a diet in which protein accounted for 35% of their caloric intake, including meat, fish, and protein shakes. At the end of the study, the subjects’ testosterone levels had decreased by 37%, which is low enough to constitute medical hypogonadism. The subjects also began to show symptoms of low testosterone levels, such as fatigue, erectile dysfunctiondepression and muscle weakness, Whittaker said Well-informed person.

While it’s a relatively small study, the significant drop in testosterone the researchers observed certainly has some implications for the popular high-protein, low-carb diets that have taken hold in recent years. According to Whittaker, the average person’s diet is only 17% protein, which means an occasional meat and egg eater needn’t worry. But someone on a high-protein diet needs to be careful, the researcher said in a statement.

While the most severe drops in testosterone were seen among men whose protein intake was 35% or more, Whittaker cautions that even the lowest levels of protein intake can have an adverse effect on testosterone, suggesting that high-protein dieters limit their protein intake to “no more than 25 percent.”

In addition to more immediate risks like erectile dysfunction and fatigue, low testosterone is also linked to long-term health consequences like cardiovascular disease, diabetes, and Alzheimer’s. Additionally, the researchers also noted that high-protein, low-carb diets lead to higher levels of cortisol, also known as the stress hormone. Elevated cortisol levels can suppress the immune system and increase the risk of disease and infection.

So while a high-protein diet may seem like the healthiest way to stay strong and lean, it seems that too much protein can wreak havoc on your health. As always, balance is key, so if you want to keep your testosterone levels in check, maybe add a carb every once in a while and ditch the raw eggs, Rocky.