Can Protein Supplements Increase GLP-1?

What Is GLP-1 And What Does It Do?

Author: Dr. Stephen Chaney

I don’t need to tell you that GLP-1 (glucagon-like peptide 1) drugs are all the rage. Total spending on GLP-1 drugs in the United States exceeded $71 billion in 2023, a 500% increase in just 5 years. There are 15 million Americans on GLP-1 drugs at any one time. And most of this increase has been driven by the weight-loss market.

Let me be clear. These drugs work. For people with poorly controlled type 2 diabetes or severe obesity-related health issues, they can be a godsend. But like any “quick fix” weight loss drugs they are overprescribed.

And when you have millions of people taking a drug, you need to take a serious look at side effects. The most frequent side effects are:

  • Nausea
  • Vomiting
  • Diarrhea
  • Constipation
  • Increased heart rate.
  • Hypoglycemia
  • Allergic reactions

These are side effects that aren’t life threatening and are easily detected. When someone experiences these side effects, they usually give their doctor a call, and their doctor either takes them off the drug or modifies the dosage.

However, more recent studies have identified two additional side effects that are much more troubling.

  • The first is depression, anxiety, and suicidal thoughts.
    • These are symptoms that many patients may not associate with the drug, especially if they already have these tendencies.
    • And the consequences can be life threatening. There have already been reports of suicides of people on GLP-1 medications.
  • The second is loss of muscle mass.
    • This is a particular concern for seniors who struggle to maintain muscle mass as they age.
    • And this is a silent symptom. Most seniors don’t realize they are losing muscle mass until it significantly affects their quality of life.

And, of course, the biggest drawback of GLP-1 drugs is that they are only a temporary fix. Unless someone changes their lifestyle, the weight comes roaring back as soon as they quit using GLP-1.

So. It’s no wonder some people are asking whether it is possible to increase their GLP-1 levels naturally without the side effects associated with GLP-1 drugs. I will discuss this below, but first I should review what GLP-1 is and what it does.

What Is GLP-1 And What Does It Do? 

Let me start by reviewing the hormones insulin and glucagon to create a proper perspective for understanding the role of GLP-1.

Insulin: Almost everyone has heard of insulin. It is released by the pancreas whenever we eat, and blood sugar levels start to rise. Its role is to lower blood sugar levels.

Glucagon: Glucagon is less well known, but you can think of it as the Yin to insulin’s Yang. It is released by the pancreas when blood sugar levels fall and continues to be present until the next meal. Its role is to increase blood sugar levels and make sure that our cells get the food they need until the next meal.

GLP-1: GLP-1 stands for glucagon-like peptide 1. With a name like that, you might expect GLP-1 to have significant sequence homology with glucagon, bind to the same receptors, and have a similar effect on our metabolism. You would be wrong!

Both peptide hormones are derived from a much larger peptide called proglucagon. This is the only way that GLP-1 is “like” glucagon.

One portion of proglucagon is processed to give glucagon in pancreatic alpha cells. Another portion is processed to give GLP-1 in intestinal L cells. [L cells are endocrine (hormone producing cells) found in the intestinal mucosa.] There is very little sequence or structural homology between glucagon and GLP-1.

Their function is also very different. You can think of GLP-1 as a partner to insulin. It is released by intestinal L cells in response to the presence of nutrients (primarily protein, fat, and carbohydrate) in the intestine. It binds to GLP-1 receptors on the…

  • Pancreas to stimulate insulin release and inhibit glucagon release. This is why it helps type 2 diabetics control their blood sugar levels.
  • Stomach to reduce the rate of gastric emptying. This prolongs the feeling of fullness after each meal.
  • Small intestine to reduce gut motility, which increases transit time through the small intestine. This also prolongs the feeling of fullness after a meal. But it can also lead to gastrointestinal side effects.
  • Brain to turn down your “appestat”. This reduces feelings of hunger between meals. But at high doses, it can affect the brain in negative ways (anxiety, depression, and suicidal thoughts).

Can Protein Supplements Increase GLP-1? 

Questioning WomanYou may be wondering, “Is it possible to increase GLP-1 levels naturally without side effects?” The answer is clearly, “Yes”. Every time you eat a meal, your GLP-1 levels increase naturally.

When you eat a meal, GLP-1 levels rise within 10 minutes and remain elevated for 1-2 hours. Then enzymes present in the bloodstream digest GLP-1 and it disappears. This is the way nature intended. There are no side effects to the natural rise and fall of GLP-1 after a meal.

And protein appears to play an important role in this process. High-protein meals result in higher and more prolonged GLP-1 levels than high-fat or high-carbohydrate meals. That’s because protein is digested to amino acids in the intestine. And some of those amino acids bind to receptors in intestinal L-cells and stimulate GLP-1 release.

You may be wondering what this has to do with protein supplements. Theoretically, protein supplements should offer the same benefit as a high-protein meal with fewer calories.

This hypothesis has been tested with a few protein supplements, and they have been shown to increase GLP-1 levels naturally. And, based on the limited data available, it appears that the increase in GLP-1 is proportional to the protein content of the supplement.

So, it appears that the answer I posed at the beginning of this article is,

  • Yes, it appears that protein supplements can increase protein levels naturally.
  • And it appears that the higher the protein content of the supplement, the greater the increase in GLP-1 levels.

However, there are many variations in the formulation of protein supplements, and we don’t know how these variations influence the effect of protein supplements on GLP-1 levels. Therefore,

  • We can’t yet say that all protein supplements increase GLP-1 levels equally.
  • When choosing a protein supplement, you should ask for clinical studies with their product showing it increases GLP-1 levels.

What Does This Mean For You?

If you can raise your GLP-1 levels naturally with high-protein meals and protein supplements, you might be asking, “What makes the GLP-1 drugs different?” To understand the answer to that question, you first need to know what GLP-1 drugs are.

  • GLP-1 drugs mimic the natural GLP-1 peptide.
  • However, GLP-1 drugs have been genetically modified to make them resistant to enzymatic digestion. They can stay in the bloodstream for up to 24 hours.

This is what makes them so effective as weight loss drugs. But it’s not nice to fool with mother nature. This is also why they have side effects.

And let’s remember that while GLP-1 drugs are effective, you will need to take them for the rest of your life unless you change your diet and lifestyle. And with long-term usage of the drugs, you are likely to experience one or more of their side effects at some point.

So, if you are willing to change your diet and lifestyle, it may be worthwhile looking at increasing your GLP-1 levels naturally. The effect may not be as strong as with the GLP-1 drugs, but it may help you suppress your appetite enough to successfully implement your lifestyle changes. You have lots of options.

  • Every time you eat a meal your GLP-1 levels increase. And the bigger the meal, the bigger the increase. But the bigger the meal, the greater the calories. So, that’s not an optimal way to increase GLP-1 levels.
  • That’s where protein supplements come in.
  • And since you are trying to maximize GLP-1 levels with the minimum calories, I recommend a 20–40-gram protein supplement with a minimum of carbohydrate and fat. Just be sure the manufacturer has done a clinical study to demonstrate their protein supplement raises GLP-1 levels.

The Bottom Line

In this article I asked the question, “Can protein supplements increase GLP-1 levels naturally without the side effects of GLP-1 drugs?” The answer is, “Yes”. In this article I tell you:

  • What GLP-1 is and what it does.
  • Why GLP-1 drugs have side effects.
  • How protein supplements can raise your GLP-1 levels naturally without the side effects of GLP-1 drugs.

For more details read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

 ______________________________________________________________________________

My posts and “Health Tips From the Professor” articles carefully avoid claims about any brand of supplement or manufacturer of supplements. However, I am often asked by representatives of supplement companies if they can share them with their customers.

My answer is, “Yes, as long as you share only the article without any additions or alterations. In particular, you should avoid adding any mention of your company or your company’s products. If you were to do that, you could be making what the FTC and FDA consider a “misleading health claim” that could result in legal action against you and the company you represent.

For more detail about FTC regulations for health claims, see this link.

https://www.ftc.gov/business-guidance/resources/health-products-compliance-guidance

 _______________________________________________________________________

About The Author 

Dr. Chaney has a BS in Chemistry from Duke University and a PhD in Biochemistry from UCLA. He is Professor Emeritus from the University of North Carolina where he taught biochemistry and nutrition to medical and dental students for 40 years.

Dr. Chaney won numerous teaching awards at UNC, including the Academy of Educators “Excellence in Teaching Lifetime Achievement Award”.

Dr Chaney also ran an active cancer research program at UNC and published over 100 scientific articles and reviews in peer-reviewed scientific journals. In addition, he authored two chapters on nutrition in one of the leading biochemistry text books for medical students.

Since retiring from the University of North Carolina, he has been writing a weekly health blog called “Health Tips From the Professor”. He has also written two best-selling books, “Slaying the Food Myths” and “Slaying the Supplement Myths”. And most recently he has created an online lifestyle change course, “Create Your Personal Health Zone”. For more information visit https://chaneyhealth.com.

 

For the past 53 years Dr. Chaney and his wife Suzanne have been helping people improve their health holistically through a combination of good diet, exercise, weight control and appropriate supplementation.

Protein – The Longevity Nutrient

How Much Protein Do You Need?

Author: Dr. Stephen Chaney 

breaking newsIn 2016 the New York Times ran an article with the title, “Can You Get Too Much Protein?” The article asserted that most Americans were getting too much protein in their diet and that protein supplements were useless and perhaps dangerous.

At the time I wrote a “Health Tips From the Professor” article summarizing recent research showing that many people needed more than the RDA for protein and that those people were often consuming too little, rather than too much, protein.

In the 9 years since then the evidence that many Americans may not be getting enough protein has only gotten stronger.

  • The standard for protein intake used to be a “one size fits all” recommendation of 46g gm/day for women and 56 gm/day for men with slight increases recommended for pregnant and lactating women. Today we know:
    • That standard was based on outdated methodology from the 1930’s. Recent studies suggest protein intake should be at least 50% higher.
    • That standard was based on studies with healthy, sedentary adults (the adult “couch potato” crowd). Protein requirements are significantly higher for anyone who doesn’t fit that description.
  • We used to think in terms of total daily protein intake. Today we know that:
    • Protein intake should be divided equally between the 3 primary meals.
    • Protein quality is important. Protein requirements should be increased if low-quality proteins are consumed.
  • We used to worry that high protein intake might damage your kidneys. Today we know that:
    • Protein intake does not cause kidney disease. It is not a concern as long as hydration is adequate and excess alcohol is avoided.
    • Protein intake is only a concern if someone has kidney disease.

Protein – Your Longevity Nutrient

If you want to delve into the latest protein research and what it means for you, I highly recommend the book, “Forever Strong: A New, Science-Based Strategy For Aging Well” by Dr. Gabrielle Lyon.

Her book is focused on helping each of us create adequate healthy muscle mass. She says, “Adequate muscle mass is essential for health and longevity. And muscle is the only organ over which we have voluntary and complete control.”

Of course, adequate muscle mass requires both exercise and adequate protein. Dr. Lyon covers both in her book, but exercise is not my expertise, so I will only cover adequate protein intake in this “Health Tips From the Professor” article.

In her book, Dr. Lyons details recent research on the amount of protein needed to optimize muscle mass. Dr. Lyon was the one who alerted me to the fact that the current protein RDA is based on outdated methodology from the 1930’s and that actual protein needs are much higher.

Dr. Lyon concludes that most Americans are not consuming enough protein to optimize their muscle mass and that adequate protein intake is essential for longevity, metabolic function, and quality of life. Specifically, she says that optimal muscle mass:

  • Improves strength and mobility.
  • Improves blood sugar control.
  • Decreases blood triglyceride levels.
  • Strengthens the immune system.
  • Improves bone mineral density and strength.
  • Reduces all-cause mortality (risk of dying) and morbidity (risk of disease).

I will use the latest science on protein needs described in her book and in recently published clinical studies to answer the important question, “How much protein do you need?” But first I want to help you understand the dynamics of protein metabolism.

The Dynamics Of Protein Metabolism 

ProfessorMost people associate muscle mass with strength and endurance. Many understand the important role muscle mass plays in burning off excess calories and keeping us slim. But few people understand the important role that muscle protein plays in our everyday energy metabolism.

Whenever we eat a meal containing protein, we store some of the protein we eat as increased muscle mass, especially when protein intake is coupled with exercise. But muscle protein plays other very important functions. It is a precious resource.

The synthesis of new muscle in the fed state is driven by:

  • Insulin, which is released into the blood stream whenever we eat a meal.
  • Exercise because it makes muscle more sensitive to the effects of insulin.
  • The amino acid leucine, which is most abundant in high quality protein sources.

In the fed state most of our energy is derived from blood glucose. This is primarily controlled by insulin.  As blood glucose levels fall, we move to the fasting state and start to call on our stored energy sources to keep our body functioning. This process is primarily controlled by a hormone called glucagon.

  • In the fasting state most tissues easily switch to using fat as their main energy source, but…
    • Red blood cells and a few other tissues in the body are totally dependent on glucose as an energy source.
    • Our brain is normally dependent on glucose as an energy source, and our brains use a lot of energy. [Note: Our brain can switch to ketones as an energy source with prolonged starvation or prolonged carbohydrate restriction, but that’s another story for another day.]
  • Because our brain and other tissues need glucose in the fasting state, it is important to maintain a constant blood glucose level between meals.
    • Initially, blood glucose levels are maintained by calling on carbohydrate reserves in the liver.
    • But because those reserves are limited, our body starts to break down muscle protein and convert it to glucose as well – even in the normal dinner/sleep/breakfast cycle.

Simply put, in addition to its other important roles in the body, muscle protein is also an energy store. You can think of it like a bank.

When we eat, we make a deposit to that energy store. Between meals we make a withdrawal from that energy store. When we are young the system works perfectly. Unless we fast for prolonged periods of time, we are always adding enough muscle protein in the fed state to balance out the withdrawals between meals.

But there are many physiological situations where protein metabolism becomes unbalanced, either because protein breakdown is accelerated or because protein synthesis is diminished. In each of those situations, our protein needs are increased.

I will describe each of these situations and how they affect our protein needs in the section below.

How Much Protein Do You Need? 

couch potatoThe Coach Potato Group: If this is you, I won’t be judgmental. But I highly recommend you read Dr. Lyon’s book. It may just inspire you to increase your fitness level and your protein intake.

As I said before the standard RDA recommendation for the coach potato group is 46 gm/day for women and 56 gm/day for men. That’s based on 0.36 grams of protein per pound of body weight and assumes that women weigh around 127 pounds and men weigh around 155 pounds.

There are two major problems with the standard protein RDAs:

1) The protein RDA should not be a “one-size-fits-all” recommendation. The standard used to calculate the RDA is based on weight. If you are a woman weighing 127 pounds or a man weighing 155 pounds, you are to be congratulated. But in today’s world the average woman weighs 170 pounds, and the average man weighs 201 pounds.

  • That means the average protein requirement should be 61 gm/day for women and 72 gm/day for men.
  • And that’s just the average. Your protein requirement is based on your weight.

2) As I mentioned earlier, the 0.36 gm/pound standard is based on outdated methodology from the 1930’s. Based on current technology, Dr. Lyon says the standard should be closer to 0.54 gm/pound.

  • If you use that standard and use the current average weight for men and women, the average protein requirement for the couch potato group is closer to 91.5 gm/day for women and 108 gm/day for men.
  • And since protein intake should be divided equally between meals, that amounts to 30 gm/meal for women and 36 gm/meal for men. If you weigh significantly more or less than the average American, you should adjust your intake accordingly.

The Over 50 Group: When we are young muscle protein deposits in the fed state and muscle protein withdrawals during the fasting state are in balance. And if we add exercise and increase our protein intake, it’s pretty easy to increase our muscle mass.

But once we reach our Golden Years things start to change. Muscle protein synthesis becomes less efficient. We need to increase the intensity of our workouts and increase our protein intake just to maintain our muscle mass.

If we fail to do that, we gradually lose muscle mass as we age, a process referred to as sarcopenia. Between 50 and 60 we lose 5-8% of our muscle mass, and the rate that we lose muscle accelerates with each subsequent decade. And that loss of muscle mass has severe consequences. For example:

  • It interferes with daily activities like playing with our grandchildren and engaging in activities we love.
  • It decreases our metabolic rate which increases our risk of obesity and obesity-related diseases.
  • It increases our risk of falls.

In short, our quality of life is diminished, and we become unhealthy and frail.

Dr. Lyon describes the training program needed to prevent sarcopenia as we age in her book Forever Strong. But we also need more protein.

On average older adults need around 35 – 45 gm of protein per meal to prevent sarcopenia. There are not enough published studies for me to provide more specific recommendations. But here are some guidelines:

  • If you are at ideal weight and in your 50’s or 60’s, you can probably do well at the lower end of the range.
  • If you are overweight or in your 70’s or 80’s, you should probably aim for the upper end of the range.
  • I recommend getting a body composition test on an annual basis and adjusting your exercise and protein intake based on your change in muscle mass. My doctor has a simple device for measuring my body composition as part of my annual physical. If your doctor doesn’t have a device like that, find out who does in your community.

Happy woman on scaleThe Weight Loss Group: If you are actively trying to lose excess weight, I congratulate you. But the sad fact is that up to 35% of weight loss on most diets comes from muscle, not fat.

That’s because your body interprets caloric restriction as starvation and increases the rate of protein breakdown.

But you can prevent that by adding resistance training to your diet plan and increasing your protein intake. By increasing your protein intake from 15% of calories (which is what most Americans get) to 30% of calories, you can rebalance muscle metabolism by increasing muscle protein synthesis. When you do this, you can reduce muscle loss to less than 10% of weight loss.

You may be wondering, “Why set the recommendation as a percentage of calories rather than gm/pound or gm/meal”. The answer is simple. Your caloric intake changes significantly you are on a diet, so expressing protein as a percentage of calories makes more sense.

For example, 30% of calories on a 1,000-calorie diet translates into 25-30 gm/meal. You might look at that recommendation and say, “That’s less than you recommended for the couch potato who is not trying to lose weight.” My answer would be, “Yes, but the couch potato is eating 2-3-times more calories.

So, the recommendation that’s easiest to understand if you are trying to lose weight is to aim for 25-30 gm of protein/meal/1,000 calories per day.  

  • Adjust your protein intake per meal based on the daily calories allowed on your diet. 
  • And if you are on a diet that restricts the kinds of food that you can eat or the amount of time you can eat, track your actual caloric intake for a few days. The “hidden secret” behind those diets is that most people eat fewer calories because of the restrictions.

Final thought: The latest data suggest that GLP-1 drugs accelerate the muscle loss associated with dieting. This is a significant concern, especially for people over 50. Some experts are recommending as much as 35-50 gm of protein/meal if you are using a GLP-1 drug to aid your weight loss.

Weight TrainingThe Fitness Group: The question I get most often from the fitness group is, “How much protein do I need after my workout to maximize recovery and muscle gain?” This has been well researched, and the answer is age dependent.

  • If you are in your 30’s, most experts recommend 15-20 grams of protein after your workout.
  • If you are in your 60s, most experts recommend 30-35 grams of protein after your workout.
  • While precise recommendations are not available for every age, you can extrapolate from these numbers.

Does Protein Quality Matter? 

I’m often asked whether all proteins are equally effective at building muscle mass or does protein quality matter? The answer is, “Yes. Protein quality matters, but not in the way that we have thought about it in the past.”

We used to think that protein quality was measured by the balance of all the essential amino acids. While balance is important, the increase in muscle mass is driven primarily by the amino acid leucine. That’s because leucine is the only amino acid that directly stimulates muscle protein synthesis.

Simply put, proteins that are high in leucine are used more efficiently by our bodies to increase muscle mass. In fact, Dr. Lyon measures protein quality solely based on its leucine content.

Many studies have looked at the optimal amount of leucine content in protein. The numbers vary somewhat from study to study, but they average around 1 gram of leucine for every 10 grams of protein.

If you look at the leucine contents of various proteins, it is clear that a 1:10 ratio is primarily found in animal proteins. Soybeans are the only vegetable protein source that comes close.However, there are many health reasons for consuming a primarily plant-based diet. Dr. Lyon doesn’t tell her patients to avoid plant proteins. But if they are consuming primarily plant proteins, she recommends that they increase their protein intake by 35-45%, so they will be getting enough leucine to maximize muscle protein synthesis.

What Role Do Protein Supplements Play? 

Protein SupplementRemember that New York Times article that said protein supplements were useless and perhaps dangerous? That’s outdated advice. In fact, you should view protein supplements as essential for reaching your protein goals.

That’s because our protein intake needs to be divided equally between our 3 major meals, but that’s not how we eat. Most of us have no trouble getting 30-40 grams of protein at dinner, but…

  • We only get around 15 grams of protein at breakfast, and…
  • 15-20 grams of protein at lunch.

But that’s assuming we eat a typical breakfast or lunch. If we eat…

  • An unhealthy breakfast of croissants and coffee or a healthy breakfast of cornflakes, skim milk, and fruit slices, we only get around 6 grams of protein.
  • A healthy green salad for lunch, we may get as little as 2 grams of protein.

A recent study has shown that adding a protein supplement to your low protein meals can help you increase your muscle mass in as little as 24 weeks.

What Does This Mean For You? 

how much protein do athletes needProtein is your longevity nutrient. My advice is:

  • Use the information in this article to set your protein goals (Talk with your doctor first if you have any health issues that may limit your protein intake).
  • Use a simple protein tracker to identify your low-protein meals.
  • Add additional protein foods or supplements to your low-protein meals to bring your protein up to recommended levels.
  • Focus on high-leucine protein foods and supplements. (If you eat more plant protein than animal protein, as I do, increase your recommended protein intake by 35-45% to make sure you are getting the leucine you need to maximize your muscle mass.)

As for what kind of protein supplement, I recommend a plant protein supplement with added leucine.

The Bottom Line 

In her book, “Forever Strong”, Dr. Gabrielle Lyon says, “Adequate muscle mass is essential for health and longevity. And muscle is the only organ over which we have voluntary and complete control.” She goes on to state that the current RDAs for protein intake are outdated. And if we look at protein needs based on the latest research, most Americans aren’t getting enough protein in their diet to achieve adequate muscle mass.

In this article, I summarize her findings. And based on the latest research, I provide protein intake recommendations for:

  • Adult couch potatoes.
  • Fitness enthusiasts.
  • People over 50.
  • People who are trying to lose weight.

I also discuss protein quality and protein supplements.

For more information on these topics and what they mean for you, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

 _____________________________________________________________________________

My posts and “Health Tips From the Professor” articles carefully avoid claims about any brand of supplement or manufacturer of supplements. However, I am often asked by representatives of supplement companies if they can share them with their customers.

My answer is, “Yes, as long as you share only the article without any additions or alterations. In particular, you should avoid adding any mention of your company or your company’s products. If you were to do that, you could be making what the FTC and FDA consider a “misleading health claim” that could result in legal action against you and the company you represent.

For more detail about FTC regulations for health claims, see this link.

https://www.ftc.gov/business-guidance/resources/health-products-compliance-guidance

______________________________________________________________________

About The Author 

Dr. Chaney has a BS in Chemistry from Duke University and a PhD in Biochemistry from UCLA. He is Professor Emeritus from the University of North Carolina where he taught biochemistry and nutrition to medical and dental students for 40 years.

Dr. Chaney won numerous teaching awards at UNC, including the Academy of Educators “Excellence in Teaching Lifetime Achievement Award”.

Dr Chaney also ran an active cancer research program at UNC and published over 100 scientific articles and reviews in peer-reviewed scientific journals. In addition, he authored two chapters on nutrition in one of the leading biochemistry text books for medical students.

Since retiring from the University of North Carolina, he has been writing a weekly health blog called “Health Tips From the Professor”. He has also written two best-selling books, “Slaying the Food Myths” and “Slaying the Supplement Myths”. And most recently he has created an online lifestyle change course, “Create Your Personal Health Zone”. For more information visit https://chaneyhealth.com.

For the past 53 years Dr. Chaney and his wife Suzanne have been helping people improve their health holistically through a combination of good diet, exercise, weight control and appropriate supplementation.

 

 

Do High Protein Diets Reduce Testosterone?

What Does This Study Mean For You?

Author: Dr. Stephen Chaney

protein foodsLow carb diets are all the rage. Everywhere you turn you see articles proclaiming how healthy they are.

When you remove carbohydrates from the diet, you need to replace them with something. So, many of these diets are high in protein. And many people are choosing the high protein versions of low carb diets. For example:

  • High protein, low carb diets have become popular for weight loss.
  • And in our society, high protein diets are considered a good thing. We associate protein consumption with strength, energy, and virility. So, many athletes also include high protein, low carb diets as part of their training regimen.

Are high protein, low carb diets the best choice? Perhaps not, if the latest study is correct. This study (J Whittaker and M Harris, Nutrition And Health, 1-12, March 2022) claims that high protein, low carb diets decrease testosterone levels.

So, you are probably wondering, “Is this claim accurate?” To answer this question, I will evaluate the study and put it into perspective for you.

How Was This Study Done?

Clinical StudyThis study was a meta-analysis of 27 studies with a total of 309 participants looking at the effect of low carb diets on cortisol and testosterone levels. The participants were young (average age = 27.3), healthy, non-obese (BMI = 24.8), active males.

The selection criteria for studies included in the meta-analysis were:

  • Measurements of resting and post-exercise cortisol and testosterone levels. For simplicity, I will focus only on the testosterone results for this discussion.
  • Young, healthy male participants to minimize variation in steroid hormone metabolism due to age, sex, or disease.
  • Comparison of a low carb and high carb diets. The low carb and high carb diets averaged 18% and 58% carbohydrate, respectively.
  • Elimination of studies containing confounding variables that might affect steroid hormone metabolism such as:
    • Weight change of more than 6 pounds
    • Use of hormones, phytoestrogens, or medications.

In analyzing the data, they also compared:

  • Duration of <3 weeks or longer duration because it takes about 3 weeks for the body to fully adapt to ketone body utilization.
  • Moderate protein (average intake = 23.1% of calories) versus high protein (average intake = 48.8% of calories) intake. [Note: For comparison, the average protein intake for adults in this country is ~16%, with some experts recommending 17-21% to prevent weight loss as we age.]

Do High Protein Diets Reduce Testosterone?

Question MarkThis study looked at the effect of low carb diets on both resting and post-exercise testosterone levels.

  • Moderate protein, low carb diets had no consistent effect on either resting or post-exercise testosterone levels.
  • However, high protein, low carb diets reduced both resting and post-exercise testosterone levels.
    • The effect on resting testosterone was highly significant. High-protein, low carb diets caused a 37% decrease in resting testosterone levels.
    • The effect on post-exercise testosterone was smaller, but still significant.

In the words of the authors, “High-protein, low carb diets greatly decreased resting and post-exercise total testosterone…Individuals consuming such diets may need to be cautious about adverse endocrine effects.”

Is There A Good Metabolic Rationale For These Results?

ProfessorAs a biochemist, I always like to look at the metabolic rationale for the results. And there is a good metabolic rationale for the effect of high protein diets on testosterone levels:

  • When protein is metabolized ammonia is released, and excess ammonia is toxic.
  • To combat ammonia toxicity the body has a metabolic pathway called the urea cycle. It removes ammonia from the bloodstream and converts it to urea, which is excreted in the urine.
  • The ability of the urea cycle to remove ammonia from the bloodstream is limited. High protein intakes can overwhelm the ability of the urea cycle to remove ammonia. This typically occurs when protein intake exceeds 35% of calories.
    • In situations like this, the body produces cortisol, and cortisol upregulates the urea cycle so it can handle the excess ammonia.
    • For reasons that aren’t entirely clear, cortisol and testosterone are regulated oppositely. Whenever cortisol goes up, testosterone goes down.

To be clear, I am not saying this is what is happening. I am merely saying this is a plausible mechanism for explaining the fall in testosterone levels on a high protein diet, and many popular low carb diets are also high protein diets.

What Does This Study Mean For You?

questionsLast week I expressed skepticism about a recent study that had excellent experimental design but did not have a plausible metabolic rationale.

This week’s study is the opposite. It has an excellent metabolic rationale, but the study is weak. Specifically, several of the individual studies included in this meta-analysis are weak.

The authors considered this as a hypothesis-generating study. The authors went on to say this study shows where we should focus our attention in future studies, namely on the possible health consequences of high protein, low carb diets.

I agree. I am not ready to tell you unequivocally that high protein, low carb diets will lower your testosterone levels. However, if you are consuming a high protein, low carb diet for either weight loss or because you are a body builder or weightlifter, this study is a potential red flag. It is not a definitive study, but the results are metabolically plausible. They might just be true.

You should also keep in mind that all the “benefits” of high protein, low carb diets are based on short-term studies. There are no long-term studies on the benefits and risks of high protein, low carb diets. There is also no historical precedent for life-long adherence to a high protein, low carb diet.

  • We are omnivores. Our ancestors ate whatever nature provided. There were times when our paleolithic ancestors ate high protein, low carb meals, but it is unlikely any of them had the luxury of eating that way for a lifetime. That is a 21st century luxury.
  • If you plan to consume a high protein, low carb diet for an extended period of time, you are part of an uncontrolled experiment with an uncertain outcome.

In case you were wondering whether this applies to any high protein (>35% of calories from protein), diet which exceeds the ability of the urea cyclic to remove a toxic byproduct of protein metabolism, the answer is “We don’t know”. However, the typical American diet is around 55% carbohydrate and 20-35% fat. It would be extremely difficult to exceed 35% protein without significantly reducing carbohydrate intake. 

The Bottom Line

A recent study looked at the effect of high protein, low carb diets on testosterone levels. It found:

  • Moderate protein, low carb diets had no consistent effect on either resting or post-exercise testosterone levels.
  • However, high protein, low carb diets reduced both resting and post-exercise testosterone levels.
    • The effect on resting testosterone was highly significant. High-protein, low carb diets caused a 37% decrease in resting testosterone levels.
    • The effect on post-exercise testosterone was smaller, but still significant.

In the words of the authors, “High-protein, low carb diets greatly decreased resting and post-exercise total testosterone…Individuals consuming such diets may need to be cautious about adverse endocrine effects.”

I am not ready to tell you unequivocally that high protein, low carb diets will lower your testosterone levels.

However, if you are consuming a high protein, low carb diet for either weight loss or because you are a body builder or weightlifter, this study is a potential red flag. It is not a definitive study, but the results are metabolically plausible. They might just be true.

You should also keep in mind that all the “benefits” of high protein, low carb diets are based on short-term studies. There are no long-term studies on the benefits and risks of high protein, low carb diets. There is also no historical precedent for life-long adherence to a high protein, low carb diet.

If you plan to consume a high protein, low carb diet for an extended period of time, you are part of an uncontrolled experiment with an uncertain outcome.

For more details, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease.

 

Health Tips From The Professor