How Protein Functions In The Body

Weight lifters have historically consumed large quantities of protein in the belief that it would enhance muscle mass. For decades, scientists scoffed at their dietary habits because there was no research on the topic and it was believed that extra protein was just converted to fat. However, over the past decade, protein requirements of athletes particularly weight lifters have been extensively studied. As it turns out, the weight lifters have been right all along.

The recommended daily intake for protein is 36 grams for every 100 pounds of body weight each day. However, this guideline is only appropriate for sedentary or moderately active individuals. Endurance athletes and weight lifters need more protein in the diet lots more. In fact, the latest recommendations for weight lifters range between 63 and 90 grams of protein per 100 pounds of body weight about double that of most people (Campbell 2007).

Weight lifters require extra protein in the diet for several reasons. First, protein is used as a source of energy during prolonged or intense exercise. Therefore, extra dietary protein is required to make up for these losses. Second, since weight lifting increases lean tissue mass, extra dietary protein is needed to support muscle growth. Third, additional protein helps to accelerate healing from exercise-induced muscle damage (Tarnopolsky 2004).

These adaptations translate into real gains in the weight room. Athletes participating in a 12-week weight training program who ate the most protein experienced 22% greater strength gains in the squat and 42% greater gains in bench press than those who ate the least protein (Hoffman 2006).

The type of protein that is consumed also plays a role in protein’s effectiveness. The branched-chain amino acids leucine, isoleucine, and valine make up about one-third of the protein found in skeletal muscle. When branched-chain amino acids are consumed, protein synthesis is increased while protein breakdown is decreased (Bloomstrand 2006) a perfect metabolic environment for a weight lifter.

One branched-chain amino acid leucine is the most potent amino acid for stimulating muscle growth (Kimball 2006). The addition of leucine to a carbohydrate and protein meal following a workout increased protein synthesis more than just the meal without leucine (Koopman 2005). Furthermore, leucine supplementation combined with mild caloric restriction stimulates fat burning more than caloric restriction alone (Mero 1999).

A common misperception about high protein intake in athletes is that it produces excess strain on the kidneys and that it may weaken the bones. Both of the claims are false (Campbell 2007). However, athletes should attempt to attain much of their protein intake from complete proteins rich in whole food vitamins such as eggs and meats. Incomplete proteins that are commonly found in plant-based foods are not effective in stimulating protein synthesis without complementary foods or supplements that, in combination, provide all 20 amino acids. Athletes should also shy away from fatty animal foods such as well-marbled steaks or high-fat beefs since these foods have more calories and fat per serving and can hinder strength gains and fat loss efforts. Vitamin supplements should be kept to a minimum and nutritional derived from whole foods which provide natural vitamins the body can use

Overall, athletes should consume more protein than the typical person. This practice has now been scientifically proven time after time. Doubling the typical protein intake can yield big dividends in the weight room. This is a great example of where the real-world knowledge of weight lifters beats out the book-smarts of researchers.

 

References

Blomstrand E, Eliasson J, Karlsson HK, Kohnke R. Branched-chain amino acids activate key enzymes in protein synthesis after physical exercise. J Nutr. 2006;136:269S-73S.

Campbell B, Kreider RB, Ziegenfuss T, La Bounty P, Roberts M, Burke D, Landis J, Lopez H, Antonio J. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2007 Sep 26;4:8.

Hoffman JR, Ratamess NA, Kang J, Falvo MJ, Faigenbaum AD.  Effect of protein intake on strength, body composition and endocrine changes in strength/power athletes. J Int Soc Sports Nutr. 2006 Dec 13;3:12-8.

Kimball SR, Jefferson LS. Signaling pathways and molecular mechanisms through which branched-chain amino acids mediate translational control of protein synthesis. J Nutr. 2006;136:227S-31S.

Koopman R, Wagenmakers AJ, Manders RJ, Zorenc AH, Senden JM, Gorselink M, Keizer HA, van Loon LJ. Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects. Am J Physiol Endocrinol Metab. 2005;288:E645-53.

Mero A. Leucine supplementation and intensive training. Sports Med. 1999 Jun;27(6):347-58

Tarnopolsky M. Protein requirements for endurance athletes. Nutrition. 2004;20:662-668.