Rationale for Protein Supplementation

Because of protein's structure and function, this may be the easiest supplement to rationalize. But in a healthy population, protein supplementation is difficult to defend, at least in its general use among athletes. The concept that "more is better" is the conventional thinking of many users of protein supplements, especially in the bodybuilding community. Athletes tend to base their diet decisions on nutritional advice from their peers, nonscientific mentors, heroes, or idols-rather than peer-reviewed, scientific literature.

No evidence has shown a constant, linear increase in muscle mass or performance, related to protein intake. Thus, there is a physiological threshold for incorporating dietary protein into fat-free mass (FFM), or for using protein as an immediate energy substrate.

Fat-free mass (FFM) includes all portions of body tissues that do not contain fat: skeletal bones and muscles, skin, organs, and body water, as well as hair, blood, and lymph. In clinical studies, an increase in FFM usually equals an increase in skeletal muscle. Energy is the capacity to do work. The energy in food is chemical energy, which can be converted to mechanical, electrical, or heat energy.

Exercise intensity and mode, goals, type of protein and total energy intake-singularly or in any combination-influence the individual requirements for optimal protein intake. There are several reasons for ingesting supplemental protein.

To enhance recovery after exercise. One defensible reason to ingest supplemental protein is to get amino acids quickly into the blood following exercise. Research using protein and carbohydrate supplements before and after weight training has shown an enhancement of anabolic hormones compared to a non-supplemented state. Theoretically, this would enhance recovery, allowing the body to spend more time on building muscle rather than repair.

In weight reduction programs. Protein supplements replace whole food proteins to eliminate unwanted calories in order to maintain equal or positive nitrogen balance during body fat reduction as cosmetic athletes must do to compete.

Convenience. Protein supplements are used in situations when whole food is not available or not an option as with early morning workouts.

Cost. Marketers often purport lower cost per gram of nitrogen when compared to foods.

Effect of exercise on protein needs. As early as 1981, scientists Lemon and Nagle studied the effect of exercise on protein requirements. Following this review, scientists began to recommend protein intakes for athletes above the RDA. While the effect of exercise on protein metabolism was found to vary by exercise type, protein can supply from 4% to 10% of exercise energy needs. Exercise increases the oxidation of amino acids and the rate of protein turnover in lean body mass during recovery.

Furthermore, cardiorespiratory exercise alone contributes to an increase in protein requirements, ^594-605 as does resistance training. Since endurance and strength training modes of exercise elicit different morphological adaptations-protein needs, when participating in both activities, may be greater than the highest recommendation for strength training. ^609,610

Metabolism refers to the utilization of nutrients in the body-the process, by which substances come into the body and the rate that they are utilized. Lean body mass (LBM) includes all skeletal bones and muscles, skin, organs, and body water, as well as hair, blood, and lymph.

Effect of negative energy balance on protein requirements. For athletes and others pursuing body fat reduction, body fat loss goals require that a caloric deficit be maintained until the goal is reached. These individuals seek to modify their body composition. During a negative energy balance, amino acids are used to assist in energy production.

Body composition is the percentage of the body composed of fat vs. lean body mass. Body composition consists of specific categories, such as the percentage of bone mineral, body water, and hair.

In athletes, anaerobic or aerobic exercise depletes glycogen, causing an increase in gluconeogenesis. Glycogen is the principal storage form of carbohydrate energy (glucose), which is reserved in muscles and in the liver. Gluconeogenesis is the formation of glucose from fatty acids and proteins rather than from carbohydrates.

The increase in gluconeogenesis is supported by the release of branched chain and other amino acids from structural proteins in order to maintain glucose homeostasis during exercise. The hypocaloric diet establishes less than optimal glycogen stores-and when combined with increased glycogen demand during exercise-protein's energy utilization is increased. The loss of lean body mass in sedentary persons during a negative energy balance can be reduced by increasing the amount of protein in the diet, leading to a more rapid return to nitrogen balance.

Collectively, these studies show an increase in protein utilization during a hypocaloric diet, with effects that can be exacerbated by exercise.

Protein and the bodybuilder. Bodybuilders during energy balance (off-season) should follow the same protein recommendations as strength athletes. However, during negative energy balance enroute to competition-level body fat, protein requirements may dramatically increase.

To reach competitive levels of body fat, calorie intake is continually lowered while exercise-including cardiorespiratory, weight training and posing-is increased. (Competitive levels of body fat are generally unhealthy and impossible to maintain for prolonged periods.)

Each component of this regime may have additive effects on protein requirements. The body's survival mechanisms, related to increases in energy expenditure and decreases in food supply, are probably highly active during this period, forcing a continued reduction in food intake to achieve the goal. However, because of protein's anabolic requirements, protein cannot be lowered. In fact, protein intake may have to be increased in the final few weeks before competition.

During this period, the body must have an option in the use of available food for energy or muscle support. The body does not have a choice with dietary carbohydrates or fats, making them the only dispensable calories. Therefore, protein intake could be dramatically increased to theoretically lessen the obligatory loss of lean tissue during these drastic measures. It is quite common to see these athletes consuming the majority of their calories from protein in the final weeks before competition. However, during the off season, when athletes returned to normal food intake (protein at anabolic requirements and energy needs met primarily with carbohydrate and fats) and energy balance-a better anabolic environment would exist compared to maintaining this high protein intake all year.

Effect of protein on satiety. Protein's role in satiety is an important consideration. As with all macronutrients, protein activates specific satiety mechanisms and may be more satiating than fats and carbohydrates. Protein-induced suppression of food intake in animals and humans is greater than its energy content alone. This suggests that protein has a direct effect on satiety. In studies of rats and humans, a pre-load of protein suppressed their food intake for several hours, and to a greater extent, a similar energy load of fat and carbohydrate.

Athletes seeking fat loss may benefit from the satiating properties of protein. Individual digestive physiology may help determine comfort with different percentages of the macronutrients. Macronutrients are nutrients that are ingested in large quantities on a regular basis. They include proteins, carbohydrates, fats, and water. All the macronutrients are necessary to normal functions.

Macronutrient intake may include protein intake above recommendations (but within healthful guidelines) in order to feel satiated and energized daily. This would assist athletes in program adherence. In summary, protein's effects on well being and satiety may assist athletes in complying with the energy intake needed for their goals.

Whey Protein Products

Research on Specialized Protein Formulas

In recent years, marketers' focus on protein products has been to build "the perfect protein". Their objective has been an enhancement of protein synthesis, compared to food protein or standard protein supplements.

Whey protein hydrolysates are the in-vogue protein product. Special processing of whey protein-which has the highest biological value of any protein-yields small peptides that are absorbed faster into the blood stream than free-form amino acids. ⁶⁴⁴ In addition, these special blends have been found to provide greater nitrogen retention and protein synthesis in starved animals, ^645,646 burn patients, ⁶⁴⁷ and during enteral feeding of hospitalized patients, ⁶⁴⁸ when compared to other proteins. The amino acid profile of whey protein (very high in branched-chain amino acids)-combined with a manufacturing process that yields the ideal peptide lengths for rapid absorption-probably gives this special blend its benefits to injured, diseased, or starved recipients. The relevance of this to well-fed, healthy athletes is probably non-existent. However, for bodybuilders, wrestlers, or other weight-conscious athletes preparing for competition (these athletes are generally underfed and overtrained at this point), these formulas offer a viable way to meet requirements with fewer calories.

Summary

Exercise mode and intensity, current athletic condition, energy intake, goals, and type of protein can affect protein requirements additively. The timing of available amino acids (pre- and post-training), reduction of calories (while sparing nitrogen losses), convenience, and possibly cost-they are all defensible conditions for protein supplements to be a benefit. On the other hand, if athletes meet their requirements (as shown on Table 1) with food, and they maintain their desired body fat levels-no substantial evidence exists that (1) using protein supplements to replace food or (2) increasing protein intake above requirements-will enhance performance or adult skeletal muscle hypertrophy.

Recommendations of Specific Protein Dosages

Recommendations are based on intake extrapolated from studies that suggest efficacy and safety.

• As assessed from the variety of protein recommendations from the top experts, there are no set guidelines, on which to make concrete recommendations for all athletes.

• In addition, if energy intake (fats and carbohydrates) is reduced, and more protein is used for energy as with fitness athletes (such as bodybuilders and fitness competitors)-the need for this dual-purpose macronutrient increases. Requirements for weight and body-fat conscious athletes who maintain a negative energy balance for extended periods are unknown. Acute bouts with very high protein intakes seem to be nontoxic to these athletes. Protein is usually the majority of the macronutrient intake for this population during this period, but athletes should return to recommended dosages when energy intake can increase following competition.

In considering all research, not including the aforementioned condition of body fat-conscious athletes, Table 14 lists the appropriate recommendations for most athletes and exercisers. The recommendations are based on the majority of energy requirements being met by dietary carbohydrates and fats.

Table 1 - Protein dosage recommendations for athletes

The active recreational athletes category also includes other competitive athletes, not attempting body composition changes. The adaptation period is defined as significant physiological changes occurring due to participation in a new regime, progressive intensity, or high-intensity training. The adaptation period presumes that factors affecting protein requirements may be additive. Athletes participating in aerobic and anaerobic (mainly strength training) activities may need intakes at the upper end of the ranges.