April 1, 2003

Athletic Requirements of Dietary Protein: An Interview with Dr. Peter Lemon
Special feature by Alison Aulph, B.Sc.

Athletes love their protein. NFL linebackers boast of their steak-and-egg breakfasts. Gym rats strut around with water bottles full of protein shakes. Anyone who so much as hits the gym once a week has a tub of whey in the kitchen and a PowerBar in their gym bag. Yet, conflicting information exists when it comes to daily protein requirements. Muscle magazines and weightlifters describe extreme diets that contain 45% protein. Popular, high-protein diets claim that 30% of calories should come from protein. Exercise nutrition texts state that athletes should have at the most a diet of 20% protein. Meanwhile, the American Dietetic Association, U.S. Surgeon General and the American Medical Association, all recommend that the healthiest diet is the Food Pyramid. It recommends that only 15% of daily caloric intake consist of protein.

This article will set the record straight. The latest developments in exercise nutrition will be discussed with Dr. Peter Lemon. For more than 20 years Dr. Lemon has researched nutrition and exercise, concentrating on the role of protein and muscle growth. He left Kent State in 1997 to return to Canada and holds the Joe Weider chair in Exercise Nutrition at the University of Western Ontario. I had the opportunity to meet with him this year. First, however, I will briefly introduce you to protein.

Introduction to protein

Your DNA is an enormous recipe book of proteins. In each cell the 20 amino acids are assembled in accordance with the genetic code. It is the type, amount and order of the amino acids, that determines the type of protein. Once built, protein is one of the largest organic molecules and has an incredibly large array of responsibilities.

Proteins are involved in the structure and function of all living things. Proteins are the carriers of oxygen in our blood: hemoglobin is a protein. Insulin, another protein, puts glucose into our cells. Proteins are instrumental in fighting disease. All of our antibodies are proteins. Our heart beats and our bodies move because muscle contraction is caused by the interaction of two proteins: myosin and actin. Most importantly, proteins are enzymes. Within every cell, these enzymes guide the biochemical reactions that keep us alive.

Proteins also provide our body's structure. Fibrous proteins create connective tissue, nails and hair. Protein can even be broken down into glucose and used as energy, though this occurs as a last resort when the body's glycogen stores have been depleted. It is obvious that protein is an incredible organic compound. Yet despite the fact protein prevents disease, keeps our hearts beating, provides oxygen and energy to our cells, it is protein’s role in the size of biceps that garners athletic attention.

Protein and muscle development

For decades athletes have viewed high-protein diets as common sense. Muscle contains protein; therefore, to build muscles you should have enough of the raw material present. Once ingested protein is broken down into amino acids and, in turn, these enter the body's amino-acid pool. This pool is located in the body fluids and tissues, and if these sites are full, the liver and some cells. The body uses these amino acids as required and replaces them as they are depleted. If the amino-acid pool becomes empty and no new protein is eaten, muscle size and strength will deteriorate as the body breaks protein down to refill the pool.

Protein is 15% nitrogen. When the amino-acid pool is full and protein is eaten, the protein is broken down and stored mainly as fat. The liver converts the nitrogen into urea and this is sent to the kidneys where it is excreted as urine.

From this fact we get the popular term, "nitrogen balance." By measuring the amount of nitrogen in the urine, it can be determined if the diet has an adequate amount of protein. If the body has an appropriate amount of amino acids, it is in positive nitrogen balance. In this state muscle building can occur. If one is in negative nitrogen balance, proteins from the muscle are broken down to use their amino acids for more important functions. This is why too little protein in one’s diet leads to muscle loss.

Protein requirements

How much protein should a diet contain? Dr. Lemon's research has demonstrated that it depends on the activity of the individual. Regardless of this research, the recommended diet of the Food Pyramid, 55% carbohydrates, 30% fat, and 15% protein, still does not distinguish between people who live extremely active lives such as elite athletes, or sedentary individuals such as elite couch potatoes.

Dr. Lemon believes there have been no revisions for two reasons. First, a reliance on studies of people who may have had some exercise but are not at the elite-athlete level. Therefore, the government sees no real difference between those whom they perceive as being "athletic" and those who are inactive. Second, their research relies on standardized measures such as nitrogen balance. An athlete may be in positive nitrogen balance at his or her lower requirements, 15% protein, and may be increasing muscle size and strength.

Dr. Lemon primarily studies athletes and he is convinced there is an additional dietary protein requirement for both endurance and strength athletes -- especially strength athletes, since their protein levels are higher than endurance athletes.

Athletes are categorized into these two groups because of their differing protein requirements. Strength training builds muscle size because it stimulates the building of myofibrillar protein faster than protein is broken down. Endurance athletes such as cyclists and runners train their muscles to work rhythmically against a lower weight for a long period of time. This difference in training affects mitochondrial protein synthesis more than myofibrillar protein synthesis. For both groups, increasing dietary protein will ensure the amino-acid pool is full and thereby enhance protein synthesis. However, there are notable differences in the amount of protein required.

The numbers

The current recommended daily allowance (RDA) of the Food Pyramid is 0.8 grams of protein/kg body mass/day. Dr. Lemon's research demonstrates a much higher RDA for both athletic groups is necessary for optimal performance.

Strength athletes: 1.7-1.8 grams of protein per kilogram of body mass per day (or 0.77-0.82 grams of protein per pound of body mass per day)

Endurance athletes: 1.2-1.4 grams of protein per kilogram of body mass per day (or 0.55-0.64 grams of protein per pound of body mass per day)

Dr. Lemon comments, "Together, these data suggest that the RDA for those who engage in regular strength exercise should be about 212-225% of the current RDA and 150-175% of the current RDA for endurance exercisers. These are given in ranges because it is not an exact determination. As soon as you put a number on it people say ‘well, I can eat 2.0 grams and that's fine.’ One of my grad students is a bodybuilder and he consumes 4.0 grams. It may be overkill, certainly in standardized measures of protein needs, nothing indicates that high a need. I don't recommend intakes above 2.0 grams because there is no data saying they are safe, but I suspect in a healthy person going above 2.0 grams is not a problem."

Bodybuilders and fitness competitors have abnormal weight fluctuations. When determining RDA, which weight should these athletes use?

"Daily protein recommendations are designed for more typical individuals whose weight does not vary this much. For those individuals, a recommendation per kg mass is appropriate. When weight changes so much the appropriate weight is likely closer to the middle of the range. Consequently, a recommendation based on lean mass would be better as this would be much more stable. However, as you know, it is more difficult to obtain an estimate of lean mass for most, so recommendations are based on total mass."

Why increased protein requirements?

When pushed to extremes, why does the body need more protein? It is still unclear, but Dr. Lemon says it may be as simple as providing the energy and raw materials needed to build and maintain. He goes on to say:

"Maybe the individuals who consume this much are expending vast amounts of energy on training and require vast amounts of protein to maintain the muscle mass. The fate of these dietary nutrients is probably very different than in a normal person. We know, for instance, if you're inactive and you have a diet high in fat that leads to heart disease, but in athletes similar high-fat diets don't lead to those problems. It’s probably because if you're training a lot you're metabolizing the fat for energy and not storing it in your body or your arteries. Therefore, the fate of protein and carbohydrates may be very different in some one who trains hard all the time as opposed to someone who sits on the couch."

Another factor may lie with increased metabolism. "There is a correlation between muscle mass and metabolism. This was shown in studies where people increased their muscle mass through weight training, and in fact their metabolic rates had increased as well. That's why we recommend weight training for people trying to lose body fat. Even though you may not expend a huge amount of energy doing an hour of weight training, if you increase your muscle mass, your metabolic rate is elevated 24 hours a day, and each day then your energy expenditure is much higher than before. This has a significant effect on body composition. The idea is to increase your muscle mass and therefore increase your metabolic rate, and then if you're eating the same amount of food you'll actually metabolize more energy."

When to eat meat

Dr. Lemon recommends protein be eaten at every meal. For athletic performance and recovery Dr. Lemon says, "There's definitely a period of time shortly after exercise that you can benefit from nutrition. Since this time period is relatively short, we think that pre-training nutrition (immediately before you train) is very important too. My recommendation would be to eat a protein/carbohydrate mixture half an hour before you workout and the same mixture as soon as possible after the workout."

"We also need to change our approach to eating. We need smaller meals more often and we need to avoid high glycemic-index carbohydrates, or at least combine them with other foods. If you always have a source of protein when you eat, the protein slows down the absorption of the carbohydrate and minimizes the blood glucose insulin response. You therefore won't go into fat-storage mode and you won't feel hungry in a short period of time. I think you might feel hungry every three hours. If you eat every three hours you won't feel hungry and then you won't be at risk for overeating."

Too much of a good thing

It is commonly assumed that diets high in protein are hazardous to health. Dr. Lemon claims that these effects apparently are exaggerated. The excess amino acids are broken down into carbon dioxide, ammonia and water to produce energy or waste. This breakdown occurs in the liver and involves the kidneys, which is why a diets high in protein have been accused of stressing the liver and the kidneys.

Yet kidney problems do not occur at a significant rate with strength athletes who consume large amounts of protein daily. High-protein diets are also considered bad for the heart because of increased fat intake. These concerns are exaggerated because it is only in animal, not human studies, that cholesterol levels have increased with increased dietary protein. The only legitimate concern is dehydration. The extra nitrogen being secreted from the body in the form of urine, takes away with it water. Athletes on high-protein diets must be carefully hydrated. Finally, excess protein is broken down as fat so a high-protein diet may lead to increased fat stores.

In conclusion

Our traditional North American diet is already very high in protein, so it is with ease that athletes can increase their daily amounts. It should be noted that animal protein is superior to plant protein. It has high amounts of all seven essential amino acids. Though plants do contain all seven, they contain varying amounts. Some sources will be very low, while others very high. A vegetarian must consume a wide variety of plant proteins. Vegetarianism is not considered less or more healthy, it is simply more work.

Protein supplements, bars or shakes, are a good idea because of their convenience. If you are to follow Dr. Lemon's recommendation of eating small meals every three hours, and each meal contains a protein, it can be difficult. Protein shakes can be made and consumed quickly and can easily contain the desired carbohydrate/protein mixture. The bars can be thrown into bags or purchased as a grab-and-go snack. Overall, I prefer the NFL’s method of dietary protein intake: steak and eggs -- over easy.

Alison Aulph is a freelance health and fitness writer. She has a degree in biological science from the University of Guelph and is currently enrolled at the University of Western Ontario.

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