The Relationship Between Protein Intake and Testosterone

Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.


Testosterone is a crucial hormone for male health and well-being, helping you grow muscle, boost your red blood cell production and increase libido. It also helps regulate your mood and hormones to promote a healthy, happy you!

Recent research suggests that a high protein diet can reduce testosterone levels. This is because too much protein can elevate cortisol and increase Sex Hormone Binding Globulin (SHBG), which prevents free-floating testosterone from being released into the bloodstream.


Protein is a type of nutrient found in many foods. It is an essential part of a healthy diet, as it helps you build and maintain cells, tissues and organs. 

Proteins are one of three macronutrients in the body. They are needed in larger amounts than other nutrients, but how much you need depends on your age, gender and health.

What is protein?

Protein is made up of a large number of building blocks, called amino acids. These acids form long chains and are joined together by peptide bonds.

Like beads arranged on a string, these chains can twist and fold into the final protein shape. 

Amino acids vary in their chemical properties, and the order they are in a polypeptide chain determines its structure and function.

All natural proteins contain at least 20 different amino acids. The most common amino acids include tryptophan, phenylalanine, lysine and aspartic acid.

How does protein fold?

A protein's primary structure -- its amino acid sequence -- determines the way that its linear protein chain folds and intramolecularly binds.

It also sets the sequence of hydrogen bonding between amino groups and carboxyl groups in neighboring regions that can help to stabilize certain patterns of folding, such as alpha helices and beta sheets.

The resulting polypeptide is then assembled into a complex protein, with an ensemble of different formations and folds (tertiary structure).

Most proteins are composed of multiple helices and sheets, but there are some proteins that are folded in less common ways.

Protein Intake

Protein is one of the most important dietary components, as it helps build muscles, tissues, and organs. It also makes enzymes, hormones, neurotransmitters, and other molecules needed to function properly.

It’s found in animal products (such as meat, fish, and dairy) and some plant-based foods such as soy beans, nuts, and nut butters.

The International Society of Sports Nutrition recommends a minimum intake of 1.6 grams of protein per kilogram of body weight for active individuals. This is higher than the average protein intake for adults, which is 1.3 grams per kilogram of body weight.

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Can Too Much Protein Reduce Testosterone?

The fitness industry often promotes high protein diets to build muscle. 

However, while these diets high in protein can be beneficial for active indivduals, they may also lead to low testosterone levels in some men. This can increase the risk of heart disease, diabetes, and other diseases.

Testosterone is a hormone produced in the testes that is important for male health, especially for muscle building and sexual function. Lower testosterone can lead to erectile dysfunction, low sperm counts, and infertility among males.

In addition to protein, men also need plenty of vitamin D to promote optimal testosterone production. This is especially important in men with low sex hormone levels, or hypogonadism.

Many athletes use whey protein shakes as a source of high-quality proteins, but some studies show that consuming these shakes can cause a significant drop in testosterone within minutes of consumption.

High-protein diets are often touted as a way to lose fat and build muscle, but they can actually cause low testosterone levels in some people.

This happens because too much protein can reduce free-floating testosterone in your bloodstream, which is what testosterone is primarily made of.

A study published in Nutrition and Health looked at the relationship between protein intake and testosterone levels in men.

It found that people who ate 35 percent of their calories from protein experienced a significant decline in testosterone after eight weeks.

These results are not the first to show that protein can affect testosterone. A number of other studies have shown that low-carbohydrate, high-protein diets can negatively impact testosterone levels and exercise performance.

In one study, subjects on a high-protein, low-carb diet had reduced testosterone levels and were more likely to have lower sperm counts than those who ate moderate amounts of protein.

Another study showed that people on a low-carbohydrate, high-protein meal plan experienced an increase in their cortisol levels, which can lead to lower testosterone levels.

The researchers concluded that it’s not enough to simply eat more protein; you need to eat it in the right proportion. This means eating protein from a variety of sources, and avoiding refined, sugary and processed foods.

In addition to the aforementioned meta-analysis, three studies have shown that very high protein intakes (> 3.4 g/kg/day) reduce resting TT concentrations, while moderate-protein diets (1.25-3.4 g/kg/day) do not.

Nevertheless, this is not to say that all high-protein diets decrease TT; rather, it may be that a very high relative dietary protein intake, or high protein-to-carbohydrate ratio, increases TT concentrations.

Moreover, a small observational study has shown that protein-rich food sources such as organ meats or fatty fish can increase the body’s levels of phosphatidylserine, a phospholipid that increases free-floating testosterone.

In addition, some researchers believe that a diet rich in PS can enhance the anabolic response to exercise.  


Research suggests that high protein intakes can lead to reduced testosterone levels in men. This may affect their libido, which can lead to low sex drive and erectile dysfunction.

The issue of reduced testosterone has been raised by a variety of researchers who have found that a diet containing 35% protein can lead to an ill-effect.

In a study conducted at the University of Worcester, UK, participants who consumed a high-protein diet experienced decreased testosterone levels and symptoms such as fatigue, depression, and muscle weakness.

This is a significant finding as it reaffirms the importance of eating an adequate amount of protein for healthy muscle growth and repair.

However, it also suggests that excessive protein intake can inhibit the production of testosterone and cause other unwanted side effects.

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