Nutrients That Control Muscle Development

It is well established that resistance training stimulates muscle development, and that the level of muscle development may be influenced by the circulating level of human growth hormone (HGH), insulin, testosterone, and other anabolic hormones. In as much as nutrition may impact on the availability of these substances, it seems reasonable to believe that specific nutrients may play a role in muscle development. However, it is also reasonable to believe that nutrient intake would not influence the body’s production of these substances if their levels are already normal. In other words, in the absence of a specific nutrient deficiency, it is difficult to believe that taking more of a nutrient would alter the production of muscle-building hormones. Again, more than enough is not better than enough. Once you’ve provided what the cells need, providing more doesn’t help. In fact, studies are mixed and inconclusive on whether increasing the specific nutrient intake of a well-nourished subject alters the hormonal milieu.

Individual amino acids have been widely tested to determine if their intake might change the production of HGH in athletes. In fact, amino acid mixtures are the largest category of supplements used by bodybuilders.10 While some earlier studies have shown that increasing the consumption (via supplement) of the amino acid ornithine may increase HGH production, there is more recent evidence that there is no significant increase in HGH from taking, either individually or in various combinations, the amino acids arginine, lysine, ornithine, and tyrosine. In addition, there is evidence that taking a broad-range supplement containing all 20 amino acids has no effect on either HGH or testosterone production.

Two studies in the 1980s suggested that taking one gram of the amino acid ornithine and one gram of the amino acid arginine each day would help to reduce body fat and would increase lean body mass and strength if taken in conjunction with a strength training program. Food supplement vendors have used this study to claim that these amino acids stimulate HGH and increase muscle mass. However, recent studies that have used more appropriate statistical designs and procedures (incorporating a double-blind protocol where neither the subjects nor the researcher knows what subjects are receiving the nutrient and what subjects are receiving the placebo, so the outcome cannot be influenced) indicate that oral supplementation of these amino acids has no impact on strength or endurance.

When a molecule or two of ornithine is attached to a molecule of alpha-ketoglutarate, the resultant molecule (called OKG for ornithine alpha-ketoglutarate) is said to have a muscle-building affect. Although a report in the 1980s, indicated that an increased insulin production was the result of OKG administration, there are no available scientific reports to confirm that OKG actually stimulates muscle development or enhances strength. There are several other nutrients and substances that may have a controlling effect on muscular development. See table 5.3 for a summary of these substances.

The single most important factor in muscle development is assuring that the athlete has sufficient energy intake to support a larger mass. If an the athlete has an appropriate energy distribution (about 60 percent from carbohydrate, 15 percent from protein, 25 percent from fat), approximately 3,500 calories are equivalent to one pound. Therefore, for an athlete to gain one pound of muscle mass in one week, an excess of 3,500 calories needs to be consumed during that week. Divided out over seven days, that’s an excess of 500 calories each day. It is impossible to increase muscle mass by adding noncalorie-providing supplements to an existing intake. Therefore, when athletes are in a weight-stable state, it is important for them to take stock of the amount and type of food that they consume to maintain that weight. Once determined, then an additional amount of energy is required to support a larger mass.

There is sufficient evidence to support a protein intake for athletes that is approximately double that for nonathletes. This increase in requirement is due to an increase in muscle damage, some protein losses in the urine, and some breakdown of protein in normal energy metabolic cycles, all of which occur for normal regular exercise. The Recommended Dietary Allowance (RDA) for protein for adult nonathletes is 0.8 grams of protein per kilogram of body weight, and the recommended intake for athletes is approximately 1.5 grams of protein per kilogram of body weight. This difference is because athletes have a higher lean body (muscle) mass that requires more protein to sustain it. However, there is almost no survey evidence to suggest that athletes have protein intakes below 1.5 grams per kilogram. In fact, surveys show that the protein intake of athletes is commonly double (approximately 3 grams per kilogram) the recommended level. Athletes taking protein or amino acid supplements often have protein intakes that exceed 4 grams per kilogram. The one exception to this is athletes who are following vegetarian eating patterns. These vegetarian athletes tend to meet the RDA for protein, but consume less than the level commonly recommended for athletes.

Given the generally high intake of protein that athletes currently have, it makes little sense to consume more protein to support a larger muscle mass. Nevertheless, if more protein is consumed it will clearly be used to support energy requirements rather than to support tissue and hormone synthesis. In fact, it is likely that the protein intake consumed by many athletes is misinterpreted as being important for enlarging muscle mass. This excess protein is burned as energy, allowing the body to better meet the energy demands of a larger mass. Without this extra energy, the resultant energy deficit makes it difficult for the athlete to enlarge the muscle mass. It is the general consensus of studies that the extra 500 calories consumed to aid in the enlargement of muscle mass should be mainly from carbohydrates, since this is a more efficient energy source and, unlike protein, one that does not increase metabolic waste that must be excreted.

The nitrogenous wastes that are created from burning protein as an energy source results in increased urinary output, which increases the risk of dehydration. Some athletes believe that protein supplements are better or more effective in supporting lean mass than foods that are high in protein. Good food sources of protein, such as meat, fish, poultry, dairy products, and legumes in combination with cereals are all excellent. There is no evidence that taking supplementary protein is better than eating these foods. As an added benefit, these foods typically contain a great deal of zinc and iron, both of which tend to be low in the diets of many athletes and which are critically important for working muscles.