Protein For Recovery: A Detailed Look at the Studies

by Arnie Baker

Most sports drinks, fruit juices, and sodas contain carbohydrates as their almost exclusive source of calories. Some coaches and nutritionists advocate adding protein to recovery drinks, generally to speed glycogen replacement.

Is the addition of protein to sports drinks helpful in promoting recovery? Should you use a sports drink with protein? You’ll find details of the science underlying the answers to these questions below.

Protein as a Macronutrient

One of three macronutrients, along with carbohydrates and fats, proteins are important in muscle structure and metabolism. Amino acids are the building blocks of proteins. The body can make some of these amino acids, but some must be obtained through the diet. These are called essential amino acids.

Protein is needed for muscle formation. Proteins are also used to transport other chemicals in the bloodstream. Enzymes, which are proteins, are important in speeding up many body processes.

Foods that contain all the essential amino acids are called complete proteins. Foods that contain only some amino acids are incomplete proteins. Foods rich in complete proteins are meat, fish, poultry, and milk products.

Vegetarians often depend upon incomplete proteins such as nuts, grains, and legumes. However if eaten together, or within the same day, they may complement one another, providing all the essential amino acids.

Proteins may also be used by the body for energy or converted to and stored as fat. When metabolized in this way, they are expensive: They cost more than carbohydrates. Expensive protein supplements are usually a waste of money.

The U.S. Recommended Daily Allowance (RDA) of protein is 45 to 63 grams for men and 44 to 50 grams for women. Said somewhat differently, the general recommendation for protein ingestion is that it should account for 10% to 15% of total daily caloric intake, or up to about 1 gram per kilogram or 0.5 gram per pound of body weight.

If you eat a balanced diet it is very easy to meet and exceed these amounts. Some have suggested that endurance athletes consume up to 50% more, or up to 1.5 grams per kilogram or 0.75 grams per pound of body weight.

Since endurance athletes consume more calories, if they eat a balanced diet it is still very easy to meet and exceed these daily recommendations. A small minority of authorities have claimed that strength training athletes may need up to 2 grams per kilogram or 1 gram per pound of body weight.

Protein as an Aid in Recovery

We’re not interested in debating the overall daily protein requirement here. We are interested in looking at whether the timing of protein consumption is important. What this article will address is whether protein is an important component of recovery drinks or should be part of a specific recovery strategy after exercise.

At the heart of this issue is whether ingesting protein early in the recovery process improves glycogen replenishment.

Carbohydrates Fuel Muscles

Muscles are fueled by carbohydrates and fats. Since about the 1960s, it has been known that the higher the intensity of work, the more carbohydrates are burned. Carbohydrates are supplied from stores in muscles as glycogen and from the blood stream.

With prolonged moderate- or high-intensity exercise glycogen stores can be exhausted. Until these glycogen stores are replaced, the athlete’s ability to exercise repeatedly at moderate or high intensity is limited.

Sparing Glycogen

Athletes can supply carbohydrates to working muscles by eating or drinking carbohydrates while exercising. Ingested carbohydrates travel through the blood stream as glucose to muscles. Studies have shown that fueling muscles by ingesting carbohydrates can spare muscle glycogen.

There is a practical limit as to how much carbohydrates can be ingested to fuel working muscles. This appears to be roughly 300 carb calories per hour, 1.2 grams of carbohdyrate per kilogram of body mass, 0.5 grams per pound of weight, or 2 calories per pound.

Replacing Glycogen

It is widely accepted that athletes who consume carbohydrates relatively promptly after exercise, during a glycogen window, replace muscle glycogen more efficiently than those who delay eating.

Again, there is a limit as to how quickly carbohydrates can be replaced. This also appears to be at the rate of roughly 300 carbohydrate calories per hour, or 1.2 grams of carbohdyrate per kilogram of body mass, 0.5 grams per pound of weight, or 2 calories per pound.

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Protein Replacement Half Truth

Study: van Loon et al, AJCN, July, 2000

Luc JC van Loon et al published an often-quoted study in the American Journal of Clinical Nutrition, July, 2000. This research is quoted to prove that protein helps recovery. The heading Half Truth refers not to researcher van Loon, but to how his research has been manipulated in advertising.

The study was based on eight subjects. Van Loon compared (a) a carbohdyrate recovery drink to (b) the same carbohdyrate drink plus one half again as many protein calories. Subjects were fed carbohydrates at the rate of 0.8 grams per kilogram per hour, every 30 minutes, for 5 hours.

For example, a 70-kilogram, 154-pound subject would have received 28 grams (112 calories) of carbohydrates every 30 minutes.

On another occasion, in addition to receiving the same amount of carbohydrates, protein was added in the amount of 0.4 grams per kilogram per hour (0.2 grams per kilogram every 30 minutes).

For example, a 70-kilogram, 154-pound subject would have received 28 grams (112 calories) of carbohydrates and 14 grams (56 calories) of protein every 30 minutes.

Synthesis of muscle glycogen was the endpoint. Protein helped, as is dramatically illustrated in Figure 1, taken from the study. This group fared much better when receiving carbohydrates and protein than when given carbohydrates alone.

Figure 1 was widely reproduced, for example on commercial websites promoting products with protein. The full truth is that researcher van Loon examined the group a third time.

Instead of adding protein, though, this third time the group received additional carbohydrate. The additional carbohdyrate, 0.4 grams per kilogram, was the same amount calorically as the additional protein received by the group when protein was added.

For example, a 70-kilogram, 154-pound subject would have received 42 grams (168 calories) of carbohydrates every 30 minutes. With additional carbohydrates, the subjects did the best.

That is to say when the amount of calories given was the same, carbohydrates worked better than a mixture of carbohydrates and protein. This is illustrated in Figure 2.

Many commercial sport drink promoters completely ignored and continue to ignore this part of van Loon’s research in promoting their protein-recovery products.

Summary: van Loon

Important conclusions of this study are:

1. Carbohydrates in the amount of 1.2 grams per kilogram per hour are better than 0.8 grams per kilogram per hour.
2. When subjects receive the same amount of calories, straight carbohydrates are better at replacing muscle glycogen than a mixture of carbohdyrate and protein.

Protein Replacement Partial Truth

Study: KM Zawadzki et al, JAP May 1992

In an earlier study, Zawadzki also showed that the addition of protein was helpful in improving glycogen storage. Glygogen replacement was faster with carbohydrate and protein than with either carbohydrates or proteins alone.

Nine subjects were evaluated on three separate occasions. The study compared (a) 112 grams of carbohydrates—448 calories; (b) 112 grams of carbohydrates and 40.7 grams of protein—611 calories; and (c) 40.7 grams of protein—163 calories given after two hours of exhaustive cycling in a laboratory.

Muscle glycogen was examined immediately and four hours after exercise. As in van Loon’s study, the fundamental flaw in the study is that there was no (152.7 gram) carbohydrate group receiving the same number of total calories (611) as the carbohydrate-protein group.

Yes, carbohydrate and protein were better than either carbohydrate or protein alone; but more calories were given. We don’t know whether subjects given the same total amount of calories in the form of carbohydrate would have fared even better, as they did in van Loon study.

Book: Ed Burke’s Optimal Muscle Recovery

Putnam, 2nd edition, 2003

This book popularizes the notion that protein is important in “restoring, protecting, and rebuilding muscles” during and after exercise. Ed Burke, the author, was the trademark owner of R41. He was paid by PacificHealth Laboratories before his death from a heart attack in 2002. Burke wrote this book to bring his thesis to a wider audience. He also had a commercial conflict of interest.

PacificHealth Laboratories, Inc.

Protein recovery drink research has been fueled by PacificHealth Laboratories. As of February 19, 2004, the company website noted:

“The sports nutrition category, which encompasses sports drinks, protein powders and supplements, and sports bars, exceeds $2 1/2 billion in annual sales. The largest component of this market is sports drinks, which is dominated by Gatorade and similar type products.

Gatorade type products are primarily for rehydration. In the past 10 years landmark studies have shown that nutrition can improve athletic performance beyond rehydration.

PHL’s sports nutrition research program has focused on enhancing recovery of the muscle during and after exercise. In developing products and conducting trials the Company uses a number of prominent experts in exercise physiology including:

Dr. Edmund R. Burke Ph.D., Professor of Exercise Physiology, University of Colorado at Colorado Springs.
Dr. Peter B. Raven, Ph.D., Professor of Exercise Physiology, Cardiovascular Research Institute, University of North Texas Health Science Center.
Dr. John L. Ivy, Ph.D., Professor, Department of Kinesiology, University of Texas at Austin.
Dr. John Seifert, Professor of Exercise Physiology, Human Performance Lab, St. Cloud State University.”

Protein Replacement Uncertain Truth

Study: J Ivy et al, JAP, October 2002

In an article published in the Journal of Applied Physiology, John Ivy might have shown that protein helps glycogen recovery. John Ivy has received a $45,000 grant from PacificHealth Laboratories (Endurox R4) for research.

Seven subjects were studied on three occasions. This study purported to measure glycogen replenishment after (a) a carbohdyrate-protein (CHO-PRO) supplement, (b) a supplement of the same amount of carbohdyrate (low carbohydrate, LCHO), and (c) a supplement with the same caloric content as the carbohdyrate-protein mixture (high carbohdyrate, HCHO).

Muscle glycogen was measured by nuclear magnetic resonance spectroscopy, not by traditional muscle biopsy. The three supplements were given in two feedings: immediately after exercise and two hours post exercise.

There are at least three problems with this study:

1. How Much Fat?

The study muddies past research because all supplements contained some fat. How much fat is unclear.

The abstract says each of the two carbohydrate supplement feedings (LCHO and HCHO) contained 6 grams of fat. However, in the body of the article it is reported that subjects in the carbohydrate trials received only 3 grams of fat per supplement feeding. This difference would mean that groups were not isocaloric; the protein-carbohdyrate group would have received an additional 54 calories.

I asked researcher Ivy about this in an e-mail. He replied: “The subjects received a total of 6 g of fat; 3 g with each CHO supplement. We weighed out the fat supplements in 3 g amounts (in a little paper cup).”

Since the carbohydrate-protein group received a drink with fat mixed in, and the carbohydrate group received fat supplements in paper cups, Ivy’s response also implies that this was not a blinded study. The researchers knew which athletes were receiving which supplement.

2. How Many Calories?

The article is inconsistent in reporting caloric content. For example, the article states that the carbohdyrate-protein group received 80 grams of carbohdyrate, 28 grams of protein, and 6 grams of fat for a subtotal of 378 calories on each of two occasions for a total of 756 calories.

There are 4 calories for every gram of carbohdyrate and protein; there are 9 calories for every gram of fat. The expected subtotal per feeding is 486 calories; the expected total is 972 calories. Where are the missing 216 calories?

Again, I contacted the study author. Ivy wrote:

“You are correct, the calculations of kcal per supplement and fat provided are confusing and incorrect. With regard to the kcal per supplement, your calculations are correct. The CHO/PRO and HCHO supplements should each total 486 kcal. How… miscalculated the kcal per supplement, I do not know… we should have caught these mistakes.”

3. Not Enough Calories?

The total amount of carbohydrate calories given was inadequate according to other studies in literature.

If 160 grams of carbohydrates were given before the 4-hour glycogen replenishment examination took place, this equates to 40 grams per hour, or 160 calories. This is about half the 1.2 grams per kilogram per hour (roughly 300 calories per hour for a 135-pound athlete) that van Loon and others have shown to be optimal.

Summary: Ivy

We don’t really know. A researcher, paid by a nutritional supplement company, published a non-blinded study of 7 subjects in which methodological or reporting errors make interpretation impossible.

We don’t know, with any certainty, how many calories of carbohdyrate, protein, or fat any of the groups received. The carbohydrate-protein group may have received more calories. The total amount of calories received by all groups was probably low.

No Effect of Additional Protein

Study: G van Hall et al, JAP, May 2000

Five volunteers were studied on three occasions. They received one of three drinks: (a) carbohydrate-protein, (b) carbohdyrate alone, or (c) water

Subjects ingested 600 ml immediately after exercise and then 150 ml every 15 minutes for 4 hours. The solutions contained (a) 1.67 gram sucrose per kilogram per liter of body weight and 0.5 grams whey protein per kilogram per liter, (b) 1.67 gram sucrose per kilogram, or (c) water.

Since subjects received 600 ml per hour after the initial bolus, they received (a) 1 gram per kilogram per hour of sucrose and 0.3 gram per kilogram of protein or (b) 1 gram per kilogram per hour of sucrose or (c) no calories.

Muscle biopsies were analyzed for glycogen immediately after exercise, at 1.5 hours, and at 4 hours post exercise. No differences could be observed between carbohydrate-protein and carbohydrate trials.

No Effect of Additional Protein and Amino Acids

Study: RLPG Jentjens et al, JAP, August 2001

Eight cyclists performed two experimental trials.

Subjects received (a) 1.2 grams carbohydrate per kilogram per hour and 0.4 grams protein per kilogram or (b) 1.2 grams carbohydrate per kilogram per hour. Muscle biopsies were obtained immediately, 1 hour and 3 hours after exercise. No differences were found in the rate of muscle glycogen synthesis.

No Improved Performance with Amino Acids

Study: LM Burke et al, MSSE A 1164, 2003

Louise Burke studied amino acids in a carbohydrate sports drink supplement. The question was whether time trial performance after 2.5 hours of exercise was changed depending upon whether or not protein was added to a carbohydrate drink.

Recovery drinks of 8% carbohydrate and 2% amino acids were compared with 8% carbohydrate alone, and 10% carbohydrate. The 10% carbohydrate solution was calorically equivalent to the 8% / 2% solution.

After 2.5 hours of cycling at 70% of VO2 max, cyclists performed a 7 kilojoule per kilogram time trial. Eight cyclists received one of the three supplements on each of three different occasions.

In a preliminary abstract report, Burke reported insulin concentrations were the same between trials. There was no difference in fat or carbohydrate oxidation. Time trial performance was the same regardless of treatment.

Summary

Muscles, composed of proteins, contain carbohydrates and fats that are used to fuel their action. Some proteins may also be broken down during muscle use.

It makes intuitive sense to replace carbohydrates, fats, and proteins used during exercise. The critical questions are how and when.

Stored carbohydrates, glycogen, have been studied for more than half a century. Restoring glycogen promptly, in the so-called glycogen window, has been shown to improve subsequent performance in those who exercise daily. Whether protein and fat replacement needs to be as prompt as carbohydrate replacement has not been convincingly shown.

There haven’t been that many studies, the studies were small, and almost all studies have shown no improvement in muscle glycogen replacement when carbohdyrate intake was adequate or calories consumed were the same for each group.

Even if prompt protein consumption is eventually shown to improve recovery, it is doubtful that this replacement best comes from relatively expensive, advertised, incomplete, and formulated artificial products. Although sports products will be convenient and palatable for some, “real food” is probably better—more complete, balanced, tastier, and less expensive.

During high-intensity exercise, athletes cannot tolerate solid foods. They use sports drinks to replace fluids, electrolytes, and calories. Such sports drinks are convenient and formulated in concentrations generally well-tolerated by the gastrointestinal tract.

After exercise, specialty sports nutritional products are rarely required. Consider traditional snacks such as sandwiches, fruits, cookies, juices and milk for your immediate after-ride glycogen replacement. Consider for meals what your parents may have recommended: lots of carbohydrates with moderate amounts of protein and fat. And of course, lots of vegetables.

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Appendix A: Endurance Sport Nutrition

Reprinted from Endurance Sport Nutrition available at http:/arniebakercycling.com

Recommendations Pre- and Post- Event Nutrition

• Supper: Pre-event meal high in carbohydrates. If planning to exercise for more than 4 hours, or 2 hours in high heat and humidity, add salt to foods.
• Breakfast: Cyclists aim for at least 1,000 calories. Runners may not be able to eat as much-perhaps only a few hundred calories. Walkers and triathletes will be in between.
• At the event: Have easily digestible fluids and calories available in case of a start delay.
• After the event: Consume 50 grams, or 200 calories, of carbohydrates within the first half-hour and another 200 calories of carbs within the first 2 hours after exercise.

Event Recommendations

• Aim for at least 8 ounces of fluids, every 15 to 30 minutes, depending upon the heat.
• Have carbohydrate-in-water solutions (e.g. sports drinks), rather than plain water.
• Walkers: Carry a waterbottle. Cyclists: Carry two. Or use a hydration system (e.g. CamelBak).
• Try to consume at least 300 calories per hour of exercise.
• For multi-hour events consider preloading glycogen.
• For multi-hour events in conditions of heat and humidity, consider preloading with a salty diet, and during the event consume salty foods, and sodium-rich solutions and gels.

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Appendix B What Makes Good Information?

Reprinted from Bicycling Medicine & Science, 2002 available at http:/arniebakercycling.com

What’s New?

What’s the latest medical and scientific info about bicycling?

Do you read the ad copy in the magazines to figure out what might be worth trying? Do you look to the pro athletes, who are sponsored, and figure that if they do it or use it, it must be great? Do you rely on coaches, some of whom receive kickbacks if you buy on their recommendation? Do you ask your friends? Or do you just spend your time, effort, or money and try everything yourself?

For most of us, it’s a combination of all of the above, plus a little hope. And, unfortunately, that little hope is what lots of companies cash in on when they manage for example, to sell us plain old water at a couple of bucks a gallon or more.

There’s another way—the scientific way. Looking at what studies or experiments really show. The scientific way is the best way to evaluate what works and what doesn’t. The scientific method is better than opinion or guessing, but it’s not foolproof. Good sport science studies are hard to come by. Worse, unfortunately, there is sometimes bad science.

A complete review of what makes good science isn’t possible in this article, but here are a few examples of “science” problems.

Initially, only studies showing an effect tend to be published: Few publications are interested in reporting, for example, that Vitamin X doesn’t cure cancer. Once something has been accepted as working, then it is fair game for challenge. So it’s common for some substance or training method to burst on the scene for a few years, and then have its bubble burst—by being shown not to work or having undesirable side effects. Androstenediol, androstenedione, bee pollen, chromium, medium chain triglycerides, nasal dilators, and royal jelly are now out of favor.

An interested party pays for some studies. Peanuts were reported to help ballet dancers’ performance (presumably by increasing deficient caloric intake) in a study paid for by a consulting company. A company I’d guess was representing a peanut company. Peanuts may well help calorically deficient ballet dancers, but so might Häagen-Dazs ice-cream.

Worse, imagine a company that pays for ten studies from ten different sets of researchers and advertises only the findings, perhaps obtained by chance, that promote the company’s products.

Some studies appear to provide important or new information but the wrong question is being asked or answered. Recently the recovery drink R4 was shown to provide better recovery than Gatorade when 24 ounces of either was consumed between taxing exercise bouts. Sounds promising, doesn’t it? But the R4 provided almost four times as many calories. Would a couple of donuts with the Gatorade have been as good?

A problem with sport science, unlike general medicine, is that studies tend to use small groups—fewer than 20 subjects. Small groups require relatively large differences to find statistical significance.

Studies often initially appear as abstracts. These present preliminary data, are often incomplete, are less subject to peer or other review, may be withdrawn, and are often cited in promotions by sponsoring commercial companies.

Keep in mind that it’s common for studies to show apparently conflicting results. For example, over the years bicarbonate loading and caffeine have been accepted as improving human performance. Newer studies have questioned that conventional wisdom.

Each study often adds just a little piece to the puzzle. It’s important not to put too much faith in any one study.