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  Last updated: 1/27/2016

Building Blocks of all Foods

Protein is one of the three major components of our diet (fats, carbohydrates, protein) and is important to repair cell injuries (muscles/tendons/ligaments)from the microscopic trauma that occurs with exercise. It is NOT a good energy source, and serves that purpose only in malnourished states where there is a chronically negative energy (caloric) balance. (Nitrogen balance is a measure of protein metabolism. A negative nitrogen balance indicates that the protein needs of the body are not being met and protein is being scavenged from tissue elsewhere in the body to maintain essential body functions. This may lead to reduced gains in muscle mass and strength.)

Protein molecules are composed of smaller building blocks called amino acids. The majority of protein digestion (breakdown and absorption) occurs in the small intestine. Protein molecules are first split into their component amino acids (which is required to allow their absorption through the intestinal lining cells and then transported via the circulatory system to cells throughout the body. These amino acids are then used to rebuild cell proteins. Any excess protein beyond that needed for cell repair is transformed (metabolized) into either carbohydrates (gluconeogenesis) or fat. Protein itself is not stored in the body which means cell repair occurs from protein eaten that day or from amino acids scavenged from protein broken down elsewhere in the body.


The ideal daily protein requirements is controversial. The two most recent articles on the subject indicate that for the average individual (omnivore and vegan) it is in the neighborhood of 1.2 grams of protein per kg of body weight per day. (article 1, article 2).

Another study from a team of researchers from Kent State University, Ohio, and McMaster University, Ontario, led by Dr. Peter Lemon evaluated a group of 12 physically active male subjects during two months of resistance training. They found that a protein intake of 81 grams per day (0.99g per kg of body-weight for a 180 lb male) resulted in a negative nitrogen balance.

Taken together, this suggests that for the average active individual, 1.2 grams of protein per kg body weight per day is adequate. For a 70 kg man (156 pounds, 1.2 grams of protein per kg per day equals 84 grams of protein a day.

And for those of you who are upping the ante with regular resistance training, a bit more protein may be needed. To quote from a recent study: "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."

Likewise for the endurance athlete (cyclist), as far back as 1983 scientists demonstrated that two hours of exercise can drain the body of essential protein stores.

Based on this information, consider the following recommendations for daily protein intake:

Thus the average 70 kg (154 pound) 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 for the ideal 70 kg rider. And as active athletes consume more daily Calories, a balanced diet without supplements should meet these 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 (read that as "unsupplemented") diet that replaced the total Calories expended each day.

A literature review failed to find any support for protein supplements (assuming a balanced daily diet with the normal distribution of protein intake). In fact there is the potential for a DECREASE in overall performance from the appetite suppressing effects of a high protein diet which results in a decrease in carbohydrate intake and diminished pre event muscle glycogen stores.

Can you eat too much protein? In one study, protein intakes above 2.62 grams per kg of body-weight (214 grams for a 180lb male) provided no additional benefit beyond the 1.6 grams of protein/kg/day as determined by nitrogen balance studies. And at these supra-maximal levels there was an increased risk of renal urea (a byproduct of protein metabolism) overload and dehydration. Long term studies of large groups show that a high protein/low carbohydrate diet also increases the risk of kidney stones and bone loss. These findings were substantiated by a University of Texas study 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%. And finally, any extra protein Calories (beyond what you are expending per day) are stored as fat, not muscle.


A significant percentage of athletes eat a gluten 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.


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)


The ZONE is basically a Calorie restricted, high protein diet used to facilitate weight loss. It has also been proposed as a nutrition strategy to improve athletic performance, reduce body fat and increase muscle mass. It recommends consuming 40% of your daily Caloric intake in the form of carbohydrate, 30% as protein, with fat making up the other 30%. An analysis should give us some insight into the effects of a high protein diet.

If you are a 60 kg (132 pound) cyclist requiring 3000 Calories per day for your training program, a recommendation of 1.5 grams would translate into 90 grams of protein or 10-12% of your overall Calories (there are 4 Calories per gram of protein). However to reach 30% protein, you'd need to consume a massive 225 grams.

Here's what you'd need to eat each day:

However, Dr. Sears doesn't start with your Calorie needs (remember this is a Calorie restricted diet). He starts with your weight and then calculates you protein requirements. Dr. Sears recommends consuming between 0.8 and 1.0g of protein per pound of lean body mass. For an individual weighing 180lb, daily protein intake would work out between 127g and 158g per day. As he recommends that protein represent 30% of daily caloric intake, daily fat consumption (30% of Calories) works out to be 70g, and carbohydrate (40%) is 211g. The daily energy content of the Zone diet for this 180lb individual is approximately 2106 Calories. And that is how it helps you lose weight - the total Calories consumed using this approach is much less than an active athlete needs.

What are the problems with the Zone diet for an athlete? As just pointed out, the recommended carbohydrate intake for our 180lb rider was 211g of carbohydrate per day. Such a recommendation is in sharp contrast to the majority of scientific research which proves the need for adequate carbohydrate to support maximal physical performance.

For example, a recent study compared the effects of different levels of carbohydrate intake on the performance of two Swedish ice hockey team. Both teams took part in two games separated by three days. During this three-day gap, the players were assigned to one of two groups. The first group consumed a normal mixed diet that provided around 40% of energy from carbohydrate. Group two had their diet supplemented with extra carbohydrate. Energy from carbohydrate in the second group represented 60% of total energy intake. The study clearly showed an improvement in physical performance in the high carbohydrate group. Simply put, a diet containing only 40% of its calories from carbohydrate was insufficient to meet the energy needs of elite athletes.

The Zone diet's recommendations for daily protein intake are a little closer to the mark. The amount of protein required by those participating in regular exercise sessions remains a topic of considerable debate. Nevertheless, there is research to show that both endurance and strength exercise increase protein requirements.

But the Zone diet can accelerate fat loss. While it does not provide enough energy to meet the needs of a competitive athlete, it does restrict Calories and its emphasis on high levels of protein may also serve to enhance fat loss. A recent Danish study, published in the International Journal of Obesity, compared the effects of a high protein and a high carbohydrate diet on weight loss. A group of 60 subjects followed a restricted Calorie diet for six months. The participants were assigned to either a high carbohydrate or high protein diet. Those on the high protein diet consumed approximately 24% of their Calories from fat, 46% from carbohydrate, and 29% from protein. The diet for subjects on the high carbohydrate diet consisted of 28% from fat, 59% from carbohydrate, and 12% from protein. Scientists found that the high protein group lost almost twice as much fat as those on the high carbohydrate diet.

Notice the similarity between the nutrient distribution in the high protein diet (46/29/24) and the recommendations in the Zone diet (40/30/30). The group following the high protein diet consumed 11.3 Calories for every pound of body-weight each day - similar to the 11.7 Calories per pound of body-weight suggested by the Zone diet.

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.

The bottom line - The Zone diet is essentially a restricted calorie diet. For individuals wanting to lose body fat, there is no reason why the Zone diet would not prove effective. However it is unrealistic to expect that athletes will experience any significant improvements in performance as a result of the Zone diet. The recommendations for both carbohydrate and Caloric intakes are not sufficient to meet the energy requirements of regular daily training.Go high protein/low carbohydrate and you'll be chronically bonked.


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.


Protein is necessary for the active athlete, but more is not necessarily better. And this is especially so if you replace total Caloric needs with protein at the expense of carbohydrates.

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

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