If you’ve been doing research about protein intake recently, you might be freaked out by headlines declaring that high-protein diets can decrease men’s testosterone levels.
They all refer to one study that concluded: “high-protein diets cause a large decrease in resting total testosterone.”
But what about all those years of bro science that showed jacked, muscle-bound dudes swigging protein shakes by the gallon? Doesn’t protein intake increase testosterone?
In general, protein intake does not impact testosterone levels. Exceptions to this are extreme cases when protein intake is very low (<0.4g per pound of body weight) or when it is so high as a proportion of your total intake that it causes you to miss out on other macronutrients (especially carbs) in your diet.
- When protein replaces carbs to create a very low-carb diet (<12% of calories from carbs), cortisol increases, and testosterone decreases.
- A high-protein intake of up to 1.5 grams of protein per pound of body weight in an overall macro-balanced diet is a great way to support resistance training and optimize hormone levels.
- Heavy resistance training is one of several ways to increase testosterone naturally for men.
I’ll get into the science behind these points in the article below.
Why Do Some Experts Say Protein Lowers Testosterone?
The experts who claim that high protein intake lowers testosterone are basing their conclusions on a study that looked at low-carb diets and men’s cortisol and testosterone, and not specifically high-protein diets. The combination of a low-carb diet and very high protein intake resulted in lower testosterone.
When it comes to making claims about protein and testosterone (or any subject that has been studied), we can’t take any one study out of context without considering the entire body of evidence.
That is why I will go over multiple studies to give you the best, most comprehensive information on overall protein intake, protein supplementation, and resistance training and how they all tie together when it comes to testosterone.
Current Research on Protein & Testosterone
Study 1: Low-Carbohydrate Diets and Men’s Cortisol and Testosterone: Systematic Review and Meta-Analysis
This is the study that raised alarm bells with its conclusion that “high-protein diets cause a large decrease in resting total testosterone.”
Low-Carb Diets vs. High-Protein Diets
Notice that the study title is actually about low-carb diets and not high-protein diets.
The authors note that cortisol (the stress hormone that is released when demands such as an intense workout are placed on your mind and body) has an inverse relationship with testosterone so that when cortisol is increased, testosterone is decreased.
Any dietary or training changes that lead to increased cortisol could potentially decrease testosterone. Low-carb diets result in much higher cortisol after long-duration exercise.
Emphasis on Relative Intake vs. Absolute Intake
The authors’ definition of “high” or “low” for any macronutrient was based on relative terms as a percentage of total calorie intake rather than an absolute number of grams.
By their definition, an extremely low-carb diet would have to mean either a high-fat or high-protein diet (or both).
The average calorie intake in the study was ~2,870 calories per day, with the low-carb diet having only 12% (344 calories or 86g) coming from carbs.
“High protein” was defined as more than 35% of calories from protein, or at least 1,005 calories (251g). Dietary intake of up to 35% of calories from protein was considered “moderate protein.”
The average study participant was 173 lbs, so the minimum high protein intake of 251g would be ~1.5g per pound of body weight (3.2g per kg of body weight).
Assuming a participant limits fat intake to 35% of total calories and carbs to 12%, protein intake would then be 53%, or 1,520 calories (380g), which is ~2.2g per pound of body weight (4.8g per kg of body weight). This is absurdly high and far beyond what we recommend in our macronutrient breakdowns since protein is the least efficient way for the body to get energy.
A macronutrient ratio that is a majority protein would put a large strain on the body in terms of energy production. This would lead to higher cortisol and lower testosterone.
Notably, moderate protein diets did not have an impact on testosterone levels.
Overall, the study points to a link between low-carb diets and high cortisol levels, with the effect that higher cortisol has a negative impact on testosterone. Dietary intake of up to 35% protein (1.5g per pound of body weight) had no impact on testosterone levels.
- Related Article: 50-30-20 Macros: What Is It, How It Works, & Sample Meals
Study 2: Effect of Protein Intake on Strength, Body Composition and Endocrine Changes in Strength/Power Athletes
In this study, college strength & power athletes ate one of the following diets:
- Low protein: 1-1.4 g of protein per kg of body weight (0.5 – 0.6g per pound)
- Average protein: 1.6 – 1.8 g protein per kg of body weight (0.7 – 0.8g per pound)
- High protein: >2g per kg of body weight (more than 0.9g per pound of body weight)
All three diets had a similar total calorie intake.
After 12 weeks in a resistance training program, there were no significant differences between groups for muscle mass, fat mass, or resting hormonal concentrations, meaning that a high-protein diet did not increase or decrease testosterone.
- Related Article: Is 1 Gram of Protein Per Pound of Bodyweight Enough?
Study 3: Impact of Resisted Exercises and Whey Protein on Growth Hormones and Testosterone in Normal Subjects
This study looked specifically at supplementation with whey protein powder.
Participants in a six-week resistance training program either had a post-workout shake with 1.2g of whey protein per kg of body weight or no shake.
Testosterone, growth hormone, and 1RM measurements increased for both groups but showed no significant differences between the groups for testosterone. The whey protein group had significantly higher growth hormone and improvements in 1 rep max measurements.
Study 4: Testosterone Physiology in Resistance Exercise and Training: the up-stream regulatory elements
While this study does not explicitly mention protein intake, it does point out that testosterone stimulates protein synthesis, and our bodies can only make protein if they have the necessary building blocks in the form of amino acids coming from protein in the diet.
The study also noted that men’s testosterone concentration is increased directly after a heavy resistance training session.
Study 5: Testosterone and Cortisol in Relationship to Dietary Nutrients and Resistance Exercise
This study dates back to 1997, and it looked at the relationship between macronutrient intake and resting and post-exercise levels of testosterone and cortisol. Sound familiar?
The study noted significant increases in testosterone after high-intensity resistance exercise, similar to Study 4.
It also referenced an earlier study from 1987, which showed that replacing dietary carbohydrates with protein decreases testosterone.
This is when “high-protein” is described in relative terms and is achieved by reducing carbohydrate intake to “low-carb” – a key point that was glossed over in the headlines from the recent study making waves.
The study reaches the same conclusion as the meta-analysis (Study 1), which is that when protein replaces carbs to create a low-carb diet, testosterone decreases. But, the study went even further and pointed out that low-fat diets (20% of total intake) are also linked to lower testosterone.
Conclusions From These Studies
- Dietary intake of up to 35% protein (1.5g per pound of body weight) has no impact on testosterone levels. Very low-carb diets are more likely to result in lower testosterone than high-protein diets.
- High-protein diets and protein supplements do not increase or decrease testosterone levels, but they do improve muscle growth and strength.
- Heavy resistance training increases testosterone concentrations in men.
Does Eating a Certain Amount of Protein Per Day Increase Testosterone?
No, eating a certain amount of protein per day does not increase testosterone.
However, intake levels of dietary protein below the minimum recommended amount (0.4 grams per pound of body weight) would not be enough to help the body with hormone production. So, it’s possible that not eating enough protein can decrease testosterone levels.
Supplementation with protein above and beyond the minimum requirement is not shown to increase testosterone levels, although it can help with muscle mass and strength gains.
- Related Article: 30 Ways To Increase Protein Intake Without Protein Powder
Other Ways To Naturally Increase Your Testosterone
Beyond maintaining an appropriate protein intake (neither too high nor too low, e.g., 0.5-1.5g per pound of body weight or roughly 10-35% of total calories), there are many other ways to naturally increase your testosterone.
Keep in mind the inverse relationship between the stress hormone cortisol and testosterone. Actions that help to reduce stress can thereby help to increase testosterone.
1. Eat an Overall Balanced Diet With an Emphasis on Minimally Processed Whole Foods
A balanced diet with lean meats, whole grains, fruits, vegetables, nuts, and seeds will naturally provide you with a balanced mix of macro- and micronutrients (vitamins and minerals) to support your overall health, which supports your hormonal health.
2. Maintain a Healthy Body Fat Percentage
If you need help with your weight loss goals, our team of registered dietitians and nutrition coaches are excited to help you.
3. Get Enough Sleep
The majority of daily testosterone is released during sleep.
Studies have shown that chronic sleep restriction results in lower testosterone levels. Make sleep a priority with a consistent bedtime routine and schedule, and aim for at least 7-8 hours each night.
4. Exercise Regularly
As we saw, there is a strong positive link between exercise, especially heavy resistance training, and testosterone levels. Aim to include resistance training sessions at least three times per week.
Don’t overdo it with intensity or volume, though, as extremely hard and/or long training sessions are very stressful. That increase in cortisol will lead to lower testosterone.
5. Reduce Stress
Given the inverse relationship between cortisol and testosterone, it makes sense that anything that helps to reduce stress can improve testosterone. Stress isn’t just from physical demands; psychological stress also decreases testosterone.
Consider meditation, journaling, or even just spending time with loved ones as ways to reduce stress.
6. Take Supplements
Supplementing with vitamin D, especially if you live in a place that doesn’t have a sunny climate, can help to increase total testosterone levels.
If you’re lucky enough to live in a sunny place, a walk outside for even just 15 minutes can improve vitamin D levels. You also get the benefits of exercise and stress reduction all in one.
Magnesium supplementation also increases testosterone levels, and the impacts are even greater for individuals who exercise regularly.
7. Review Your Medications
Some prescription medications can decrease testosterone (most notably statins). If you are concerned about this, discuss it with your doctor or pharmacist.
8. Avoid Drug and Alcohol Abuse
Alcohol and drug abuse have negative impacts on the entire male reproductive system, including testosterone.
Eliminate or reduce alcohol intake to no more than 3-5 standard drinks per week, and avoid drugs other than prescription medications you have reviewed with your primary health care provider.
Frequently Asked Questions
Is There Testosterone In Whey Protein?
No, there is no testosterone in whey protein. But combining heavy resistance training with a diet that includes sufficient dietary protein intake (0.7-1g of protein per pound of body weight) from whey protein powder and whole foods can lead to increases in testosterone, especially for men.
Additional Protein Resources
- Is Whey Protein Good For Women? (What Science Says)
- Can You Take Whey Protein Without Working Out? (Science-Backed)
- Will I Lose Muscle If I Stop Taking Whey Protein?
About The Author
Lauren Graham is a Precision Nutrition Level 1 certified nutrition coach. She focuses on helping busy professionals balance healthy eating and purposeful movement. Lauren has a background in competitive swimming and is currently competing as a CrossFit athlete. She has a passion for training, teaching, and writing.