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  Last updated: 4/30/2019

Building Blocks of all Foods

Protein is one of the three major components of all foods (fats, carbohydrates, protein) and is required for cell repair of the microscopic trauma that is associated with exercise and training. It is NOT a particularly good energy source, but is available for that purpose in malnourished individuals.

We measure a persons nitrogen balance to assess protein metabolism. A negative nitrogen balance indicates that protein requirements are not being met by our diet and protein is being scavenged from healthy tissue to maintain essential body functions. A negative nitrogen balance will impair training gains in muscle mass and strength.

Protein molecules are built from amino acids. The protein in our diet is broken down in the small intestine into its component amino acids which are absorbed through the intestinal lining cells and then transported to cells throughout the body where they are then available to rebuild and repair cellular proteins. There is no protein storage capacity beyond the protein that is an integral part of cells throughout the body. This means cell repair requires either amino acids from protein eaten that day or from amino acids scavenged from cell protein breakdown elsewhere in the body. Any excess dietary protein - beyond that needed for cell repair - is converted into carbohydrates (gluconeogenesis) or fat.


This article summarizes the change in the answer to that question over time.

Several recent articles support a number of 1.2 grams of protein per kg of body weight per day for the average individual (omnivore as well as vegan). (article 1, article 2).

A third study from a team of researchers at Kent State University and McMaster University evaluated a group of 12 physically active male subjects over two months of resistance training. They found a protein intake of 81 grams per day (1.0 g per kg of body-weight for a 180 lb male) left the athletes in negative nitrogen balance (indicating this level was inadequate).

Taken together, these support a number of 1.2 grams of protein per kg body weight per day for an active individual. For a 70 kg man (156 pounds) that translates into 84 grams of protein a day.

Those on a regular resistance training program or endurance athletes requiring more than the average individual in training induced micro trauma repair may have a higher requirement. To quote: "Research has indicated that increased dietary protein intake (up to 1.6 g protein per kg per day) may enhance the hypertrophic response to resistance exercise."

Based on these papers I think the following are reasonable recommendations for daily protein intake:

The average 70 kg (154 pound) recreational cyclist will need from 80 to 100 grams of protein per day. And for those at the elite level, the requirement may be as high as 120 grams. As active athletes consume more Calories a day than a normally active individual, a balanced diet without supplements should meet their needs. Even in extreme endurance activities such as the Tour De France, estimated protein needs of 1.5 gms protein/kg body wt/day were easily met by a normal (or "unsupplemented") diet that met total daily Caloric needs.

A literature review failed to support the use of protein supplements on a balanced daily diet (a normal distribution of protein/carbohydrates/fats). In fact it was suggested a potential for a DECREASE in overall performance from the appetite suppressing effects of a high protein diet which in turn led to a decrease in carbohydrate intake (and pre event muscle glycogen stores).

Can you eat too much protein? One study with protein intakes of over 2.5 grams per kg of body-weight along with showing no additional benefit above the 1.6 grams of protein/kg/day need (as determined by nitrogen balance studies) also suggested an increased risk of urea (a byproduct of protein metabolism) overload and dehydration at these supra-maximal levels. Longer term studies of large groups show a high protein/low carbohydrate diet increases the risk of kidney stones and bone loss. In a study from the University of Texas of 10 volunteers on a high protein/low carbohydrate diet for two weeks blood uric acid levels (uric acid is a major cause of kidney stones) rose 90% and urinary levels of citrate (which inhibits kidney stone formation) dropped 25%. A final risk is the potential for weight gain as any extra protein Calories (beyond those expend) are stored as fat, not muscle.


The US Recommended Dietary Allowance (RDA) for protein intake is 0.8 g/kg/day for adults. But as we have just read, this may be on the low side for an athlete. How did that happen? Most likely as the recommendation is based on nitrogen-balance studies in average young adults who almost certainly have varying athletic leanings.

And it is probably too low for older adults who are less efficient in their protein digestion and absorption. It has been speculated that too little dietary protein and as a result being relatively relative protein deficient, may be an aggravating factor in the loss of muscle mass that accompanies aging.

Taking both aging and activity level into account, an international panel of experts recommended protein intakes of 1.0 - 1.2 g/kg/day for all adults 65 years or older, with even higher intakes for those who are more physically active.

So for all of us who are riding regularly, and often competitively - even if just with friends on the weekend, it is important to keep an eye on the protein content of our diets.

I have never been a fan of the over response with the paleo diets as the red meat comes along with a lot of undesirable fats. So if you want to err on the side of caution, there are plenty of non meat sources of protein to add to your diet.


Lean beef, skinless chicken, and fish will provide about 7 grams of protein per ounce ( quick online reference}. Beans will provide 6 grams per 1/2 cooked cup, and rice (and other cereal grains) about 3 grams per 1/2 cup serving. A cup of milk or yogurt supplies 8 grams of protein. So it's relatively easy to meet your basic protein requirements from 6-8 ounces of meat, 2-3 servings of dairy products, and 6-10 servings of cereal per day. And how about soy? For soy (tofu) it is 2.5 grams protein per ounce of tofu (10 grams protein per half cup or 4 ounces tofu)


A growing number of cyclists are moving toward meatless meals or a completely meat free nutritional program. Not only are vegetarians healthier, with lower rates of chronic diseases such as heart disease, obesity, and colon cancer, but the fact that their diets are high in carbohydrates means they are constantly "carob loaded".

Vegetarians as a group do not appear to be at excessive risk for protein deficiency and in turn diminished athletic performance.But it is possible that in select individuals with rigorously self-limited selections of what they choose to eat, may be at some risk. The following is a specific example.

This is a summary from a presentation at the American College of Sports Medicine 2018 Annual Meeting as reported in an article in Medscape online. It suggests that vegetarians may be at performance risk from a lack of choline (an amino acid - a protein building block) in their diet. (Eggs were the source of choline in this study.)

A few direct quotes from the article.

Their conclusion: "It is hard to get adequate amounts of choline from plant foods, although it is present in, for example, soy beans."

A couple of my thoughts on this article:

  1. The risk of low choline consumption would be highest in those avoiding animal fat and cholesterol as part of a healthier diet.
  2. Choline deficiency is an even higher risk for vegans, who are avoiding all animal products.
  3. There was no difference between the middle and high supplementation groups so "...more is not better". You just need a threshold amount.
  4. They felt there was minimal potential for CV harm from the cholesterol in the eggs at the supplement levels studied, so an easy way to supplement your diet might be to add a couple eggs a week to your diet plan.
  5. Finally, this was about development of muscle strength, not endurance. So it is unclear how it might impact aerobic performance and endurance athletes.

There are a few tips to remember if you are considering a move to less meat.


A significant percentage of athletes eat a gluten (a grain protein) free diet - feeling it helps performance. In this study from Australia ~40% of the athlete group are on a gluten restricted diet. This is twice the rate of the general public ~20%.

The incidence of clinically proven gluten intolerance (celiac disease) with documented inflammation of the small intestine is about 1% in the general population. A critical review of gluten intolerance suggested that non-celiac gluten sensitivity (NCGS - no inflammation of the bowel on endoscopic biopsy) could be as frequent as 10%. Are athletes, who are pushing their bodies to the max, more sensitive to even minimal symptoms of NCGS? Is this another example of a placebo effect? Or athletes "just buying insurance", eliminating any factor which might impact their performance. What is the data?

This study looked at the short term (2 week) impact of a gluten free diet on cycling performance or GI symptoms (which are common in elite athletes). A quote from the NYT summarizes the findings. "Cycling performance had proven to be essentially identical after a week in which a rider ate zero gluten or large amounts of gluten. Inflammatory markers likewise were indistinguishable. For their part, the riders' daily reports about the states of their digestive tracts and moods likewise showed little variation whether a rider was eating gluten or not. Over all, Ms. Lis said, 'we did not find a beneficial or negative effect of a gluten-free diet for athletes who had no clinical necessity for the diet.' "

Points to be taken away?

  1. This was a short term study. 2 weeks of gluten restriction. If you have true celiac disease, this is too short a time for gastrointestinal tract inflammation to resolve completely.
  2. This was a small study group. 13 participants. If 6 - 10% of the population have NCGS, it is likely only 1 of the study group might have suffered from that entity. And as the results are group results, a benefit might have been masked.
  3. But the most important finding, I think, is that a gluten free diet did NOT impair performance. So if you think you have NCGS, there is no clear downside to limiting your gluten intake.


There are two ways to express the daily intake of protein (P), carbohydrates (C), and fats (F). One is as the absolute number of Calories derived from each dietary component. The other is to express the balance of P/C/F as a relative ratio of the percent of total daily Calories from each. As most diet analyses are expressed in relative terms, let's use that to define a high protein diet.

What is the balance of protein/carbohydrates/fats in an "average" diet? For the average active individual, not those participating in endurance sports, on a Calorically balanced diet, not trying to lose weight, we find that Carbohydrates make up 45-65 percent of daily Calories, Fat 20-35 percent of Calories, and Protein 10-35 percent.

The current controversy on healthy eating is over the appropriate balance of total Carbohydrates versus total Fat in that average diet. There is solid evidence that IF you are not eating extra carbohydrate Calories to support special athletic energy needs, you may be healthier if you change that balance towards fewer carbohydrate Calories (neared lower range of 40 or 45 % of the daily total) with more Calories from dietary fat (nearer 35 or 40%). In a Calorically balanced diet, protein remains between 10 - 30%.

What about higher protein diets?

The Zone Diet

A couple references:

Dr. Sear's diet is based on a rigid Caloric ratio of 40% carbs, 30% protein and 30% fat along with an emphasis on carbohydrates with a low glycemic index (providing a slow release of sugar and minimal an insulin surge), lean protein, and fat that is monounsaturated. It is similar to a Mediterranean Diet.

The term diet can be used in two ways. It can refer to

The Zone diet can be used for both purposes. To lose weight you keep the correct ratio and focus on a negative Caloric balance. If you are at your ideal weight, you eat a Calorically balanced diet and move the focus to the P/C/F ratio.

Used to lose weight, evidence suggests that the Zone diet's emphasis on high protein and fat may have an advantage over other weight loss programs, not the result of the original conjecture that it facilitated fat metabolism as much as from a blunting of appetite which translated into the intake of fewer Calories per day than the comparison diets.

After analyzing the dietary intake of the groups, the research team realized those on the high protein diet had eaten less food. This accounted for the greater weight loss. There were several possible explanations for this reduction in food intake. Protein has a higher satiating (pronounced effect than carbohydrate. In other words, you feel less hungry when consuming a diet high in protein. And a high protein intake seems able to suppress the following days energy intake to a greater extent than carbohydrate.

For an athlete on any weight loss program, there is a significant risk of riding in a metabolic state similar to that experienced with being "bonked" (when your glycogen is depleted and no external glucose has being taken in). Dr. Sear's feels that it is this lack of glycogen that forces the body to "burn" extra fat assisting with weight loss. Riding bonked is just part of what one should expect - on the Zone or any other weight loss diet.

If you are not trying to lose weight, keeping the exact Zone ratio is alleged to provide the health benefit from a decrease in total body inflammation and an increase in a sense of "well being". These claims have yet to be proven in long term observations.

How about a Calorically neutral Zone diet and the athlete? Where Calories eaten are adequate to replace those expended each day?

Although the Zone Diet claims to improve performance, a study on athletes following the diet lost endurance. Why is that the case? The problem is in the rigid P/C/F ratio of 40/30/30.

If you want to maintain your weight (not gain weight) your daily Caloric expenditure and intake have to be in balance. Applying the Zone ratio to supply these Calories, an endurance athletes will not eat enough carbohydrate Calories (at 30% of the total daily Calories eaten) to meet their higher level exercise needs. With fat metabolism being less effective than carbohydrate metabolism to support high level (>50 - 60% VO2max) activity, you bonk or run out of gas.

This is demonstrated in this study "The acute 1-week effects of the Zone diet on body composition, blood lipid levels, and performance in recreational endurance athletes." Limiting daily carbohydrate Calories available (by sticking to the correct Zone ratio) led to slowly progressive glycogen depletion.

The bottom line - To lose weight, using the Zone ratio with a negative daily caloric balance works. But on a calorically adequate daily diet it is unrealistic to expect that athletes will experience significant improvements in performance. The recommendations for both carbohydrate and Caloric intakes are not sufficient to meet the energy requirements of a regular daily training program. Go high protein/low carbohydrate and you'll be chronically bonked.

The Paleo diet

The paleo diet is the ultimate high protein approach to making diet choices.

It is based on the unproven assumption that our ancestors ate a high meat diet and thus our metabolism is optimized for protein. But the data is not there to support that assumption.

First we have the facts from many population studies that demonstrate a strong correlation of health status with dietary intake - specifically the negative impacts of a high meat diet versus the positive benefits of being a vegetarian.


In his review of the literature (original abstract) on dietary protein supplements, Dr. Richard B Kreider PhD (Department of Human Movement Sciences & Education, The University of Memphis, Memphis, Tennessee 38152. Email: concluded that "dietary supplementation of protein beyond that necessary to maintain nitrogen balance does not provide additional benefits for athletes."

Here is an excerpt of his review:

BACKGROUND. Protein and amino acids are among the most common nutritional supplements taken by athletes. This review evaluates the rationale and potential effects on athletic performance of protein, purported anabolic amino acids, branched-chain amino acids, glutamine, creatine, and hydroxymethylbutyrate (HMB). LITERATURE. Two books, 61 research articles, 10 published abstracts, and 19 review articles or book chapters. FINDINGS. Dietary supplementation of protein beyond that necessary to maintain nitrogen balance does not provide additional benefits for athletes. Ingesting carbohydrate with protein prior to or following exercise may reduce catabolism, promote glycogen re-synthesis, or promote a more anabolic hormonal environment. Whether employing these strategies during training enhances performance is not yet clear. There is some evidence from clinical studies that certain amino acids (e.g., arginine, histidine, lysine, methionine, ornithine, and phenylalanine) have anabolic effects by stimulating the release of growth hormone, insulin, and/or glucocorticoids, but there is little evidence that supplementation of these amino acids enhances athletic performance. Branched-chain amino acids (leucine, isoleucine, and valine) and glutamine may be involved in exercise-induced central fatigue and immune suppression, but their ergogenic value as supplements is equivocal at present. Most studies indicate that creatine supplementation may be an effective and safe way to enhance performance in intermittent high-intensity exercise and to enhance adaptations to training. Supplementation with hydroxymethylbutyrate appears to reduce catabolism and increase gains in strength and fat-free mass in untrained individuals initiating training; as yet, limited data are available to decide how it affects training adaptations in athletes. CONCLUSIONS. Of the nutrients reviewed, creatine appears to have the greatest ergogenic potential for athletes involved in intense training. FURTHER RESEARCH. All supplements reviewed here need more evaluation for safety and effects on athletic performance.

Potential risks of excessive dietary protein or protein supplements include:

What about protein in combination with carbohydrates in energy and post recovery drinks? It had been suggested at one time that protein/cho mixtures were more effective than CHO alone in repleted or supplementing muscle glycogen stores. The final word, in my mind, is a review of 26 studies, published in 2014. The conclusion: "When carbohydrate is delivered at optimal rates during or after endurance exercise, protein supplements appear to have no direct endurance performance enhancing effect. " And in addition, they expanded that conclusion to include supplements while riding as well as in the post ride recovery period: "...when carbohydrate supplementation was delivered at optimal rates during or after exercise, protein supplements provided no further ergogenic effect, regardless of the performance metric used."

Theoretically, in intense exercise, protein post ride may help jump start the muscle repair process. But this is theory and I am unaware of any studies that support this idea. The one reason protein might be considered in a supplement or recovery drink in conjunction with CHO would be to improve taste and in that way optimize supplement use (maximizing Calories replaced) both during and after a ride. This could be especially important for those riders who do not tolerate very sweet sugary drinks.


Cholesterol and saturated fats have been tagged as major risk factors for blood vessel disease (atherosclerosis) for decades. But recent work suggests they are not the most important factor in all those heart attacks. Merely a late stage contributor to damage already well under way.

The results of numerous studies and investigations points to Trimethylamine N-Oxide (TMAO) as the real culprit.

There is proof of cause and effect. In an experimental mouse model, raising blood TMAO levels by dietary manipulation increased blood vessel disease in the absence of any changes in the cholesterol or fat content.

Numerous clinical studies of heart disease (chest pain in the ER, progression of known atherosclerotic heart disease) show a direct correlation between increasing blood levels of TMAO and cardiovascular disease.

Carnitine, a protein found in red meat and to a much lesser degree in chicken and fish, is the source of TMAO. Any dietary carnitine not digested and absorbed in the small bowel passes into the colon where bacteria (our microbiome) metabolize it to an intermediate molecule, TMA. TMA is in then absorbed and modified further in the liver to TMAO.

There is a similar pathway for the production of TMAO from lecithin, a protein found in egg yolks.

Solid evidence supports diet as the major determinant of blood TMAO levels. A recent study documented that a diet low in red meat and eggs lowered TMAO levels independent of the amount of cholesterol or saturated fats in those diets.

TMAO production can be reduced with oral antibiotics (which alter the makeup of the microbiome) or by decreasing the dietary intake of carnitine. Vegans as a group have the lowest blood TMAO levels (and the lowest rate of cardiovascular diseases) while those on a regular red meat diet the highest. just replacing red meat with chicken will lower the amount of TMAO excreted in the urine by two thirds.

What does this suggest for your diet?

  1. Saturated fats, found in butter, cheese, red meat and other animal-based foods, do play a role in the development of cardiovascular disease, but there risk has been overstated.
  2. Your decision on the source of the third component of the daily diet, protein, has considerable impact on your health. We know that vegetarians have the lowest levels of blood vessel disease, and your goal should be a move toward a meat free diet. But that does not mean you have to move to a full vegetable protein oriented diet. You can cut your risks by adding one or two meat free dinners a week. Or decrease red meat portion sizes. And now we know that your choice of animal protein should focus on substituting chicken or fish for red meat as much as possible.


Protein is necessary for the active athlete, but more is not necessarily better. And for meat protein, chicken and fish are safer for your health than red meat.

Questions on content or suggestions to improve this page are appreciated.

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