Pre- and Post-Exercise Amino Acid Supplementation

The importance of protein in nutrition and health cannot be

overemphasized. Proteins are essential nutritionally because of their constituent

amino acids, which the body must have to synthesize its own variety of proteins

and nitrogen-containing molecules that make life possible. While amino acids

can be classified based on structure or properties such as net charge or

polarity, back in 1957, William Rose categorized the amino acids found in

proteins as nutritionally essential (indispensable) or nutritionally nonessential

(dispensable). At that time, only eight amino acids— leucine, isoleucine, valine,

lysine, tryptophan, threonine, methionine and phenylalanine— were found to be

essential for adult humans. Histidine was later added as an essential amino

acid.1

How Much Protein?

Clearly, athletes engaged in heavy training need more protein than the

sedentary people.2,3,4 Table 1 presents a summary of the recommended daily

protein intakes for physically active individuals.4 However, the testimonials of

hard-core bodybuilders who believe their success depends on consumption of

enormous amounts of protein, suggest that further laboratory investigations are

necessary before the question of protein need in those attempting to increase

lean mass is settled. It is possible that extremely high-protein intakes consumed

by some strength-power athletes are only advantageous when combined with

anabolic agents (i.e., anabolic-androgenic steroids).

Table 1. Recommended Protein Intakes (g/kg/day) for Physically

Active Individuals

Strength-trained, maintenance 1.2-1.4

Strength-trained, gain muscle

mass

1.6-1.8

Endurance-trained 1.2-1.4

Weight-restricted 1.4-1.8

Teenagers should add 10% to the calculated values. Data from

Williams, 1999.

Timing Makes the Difference?

Dr. Kevin Tipton and colleagues published paper in the American Journal

of Physiology examining the response of net muscle protein synthesis to

ingestion of amino acids after a bout of resistance exercise.5 Subjects

consumed in random order one liter of a mixed amino acid (40 grams) solution,

an essential amino acid (40 grams) solution, or a placebo solution. Authors

concluded that ingestion of oral essential amino acids results in a change from

net muscle protein degradation to net muscle protein synthesis after heavy

resistance exercise in humans similar to that seen when the amino acids were

infused.

Thus, these results suggest that hyperaminoacidemia from ingestion of

oral amino acids is an effective method of maximizing the anabolic effect of

exercise. Because net balance was similar for mixed and essential amino acids,

it does not appear necessary to include nonessential amino acids in a

formulation designed to elicit an anabolic response from muscle after exercise.

Another excellent study by Dr. Tipton and coworkers was designed to

determine whether consumption of an oral essential amino acid/carbohydrate

supplement before exercise results in a greater anabolic response than

supplementation after resistance exercise.6 The results indicated that the

response of net muscle protein synthesis to consumption of an essential amino

acid/carbohydrate solution immediately before resistance exercise is greater

than when the solution is consumed after exercise. According to the authors, it’s

likely that the greater delivery to the muscle during pre-exercise

supplementation accounts for the greater net uptake than during post-exercise

supplementation. Consuming a source of amino acids before exercise

increases amino acid availability. Providing amino acids at a time when blood

flow is elevated, such as during an exercise bout, maximizes delivery to the

muscle.

However, the question remained as to whether this acute response

reflected the response of muscle over a longer time period. Thus, the third study

by Dr. Tipton and colleagues was designed to determine if the response of net

muscle protein balance to resistance exercise and amino acid ingestion

previously noted on an acute basis, reflects the response of net muscle protein

balance over an entire 24-hour period. The investigators confirmed that muscle

protein balance is increased, primarily because of an increase in muscle protein

synthesis, when measured acutely, and found that this response is additive to

the basal response over a full 24-hour period.

Bottom Line

Although more research is needed, it’s my view that sports drinks

containing only carbohydrates are news of yesteryear. Although they may cut it

for endurance athletes, they are sadly lacking for hard-core strength-power

athletes. I suggest you consume a fair amount (i.e., 25-35 grams) of high-quality

protein (e.g., whey protein) both before and after training to boost muscle

protein synthesis.

Textbook Treason?

I just received two nutrition textbooks from Wadsworth/Thomson

Leaning for review: Advanced Nutrition and Human Metabolism by Groff &

Gropper and Understanding Nutrition by Whitney & Rolfes. As I read Whiney &

Rolfes, I was struck by the following statements:

“Protein supplements are expensive, less completely digested than

protein-rich foods and, when used as replacements for such foods, often

downright dangerous.”

This is not the case. Modern protein powders have a high biological

quality and are certainly not “downright dangerous”; see the review by Dr. Luke

Bucci in Energy-Yielding Macronutrients and Energy Metabolism in Sports

Nutrition (CRC Press, 2000).

“Whey protein appears to be particularly popular among athletes hoping

to achieve greater muscle mass. A waste product of cheese manufacturing,

whey protein is a common ingredient in many low-cost protein powders.

Athletes and active people who want bigger muscles should know that whey

protein does not increase muscle mass.”

There is some evidence suggesting that whey protein may enhance lean

body mass in conjunction with appropriate training (J Nutr Biochem, 14:251-

258, 2003). Whey proteins have a high biological value and contain a relatively

high proportion of branched-chain amino acids (BCAA). The abundance of

leucine in whey is of particular interest in this regard. Leucine plays a distinct

role in protein metabolism and has been identified as a key signal in the

translational initiation pathway of muscle protein synthesis.

Another point, beyond the composition of amino acids present in whey, is

the manner in which whey and other intact proteins are absorbed and utilized

relative to each other, as well as to free amino acid solutions. Whey proteins

have been compared to casein and a distinct difference is that whey is rapidly

absorbed compared to casein. Dr. Bohe and coworkers reported that

continuous stimulation of protein synthesis (via a constant infusion of amino

acids) resulted in saturation of the response within two hours (J Physiol

532:575-579, 2001).

Thus, an effective protein source would be one that could stimulate a

response in the periods between feeding which would be additive to the net

accumulation of muscle protein in the course of a day.

Further, certain amino acids and whey-derived bioactive compounds offer the

potential to extend health benefits to active people beyond body composition.

Many of the functions associated with these amino acids and whey components

involve the immune system and may therefore be of particular importance to

athletes in intensive training. The claim that certain whey peptides suppress

appetite is being used to market some products, but well designed studies to

validate this effect are lacking.

“People have reported that their blood cholesterol dropped while they

were on high-protein diet, but because no studies have been conducted, such

comments cannot be accepted as evidence.”

Three independent groups reported beneficial effects on body

composition and blood lipids derived from direct substitution of protein for

carbohydrates in adult diet (Metabolism 40:338-343, 1991; Int J Obes 23:528-

536, 1999, Diabetes Care 25:425-430, 2002). Further, Dr. Donald Layman and

colleagues recently reported that increasing the proportion of protein to

carbohydrate in the diet of adult women has positive effects on body

composition, blood lipids, glucose homeostasis and satiety during weight loss (J

Nutr 133:411-417, 2003).

“Large doses of branched chain amino acids can raise plasma ammonia

concentrations, which can be toxic to the brain.”

Not all studies have reported significant increases in plasma ammonia

following branched chain amino acid supplementation. In fact, some studies

report no effect, or that plasma ammonia or other markers of protein

degradation are decreased with BCAA supplementation.

Certainly, university textbooks should be based on a thorough analysis of

the scientific literature, not unsubstantiated fears and misrepresentations. If you

want to purchase a scientifically based sports nutrition text, I suggest that you

visit www.humankinetics.com or www.crcpress.com.

References

1. Groff JL, Gropper SS (2000) Advanced Nutrition and Human Metabolism. Belmont, CA:

Wadsworth.

2. Manninen AH (2002) Protein metabolism in exercising humans with special reference to

protein supplementation. Masters thesis. University of Kuopio Medical School.

3. Lemon PWR (1998) Effects of exercise on dietary protein requirements. Int J Sports

Nutr 8:426-447.

4. Williams MH (1999) Nutrition for Health, Fitness and Sport. New York: WCB/McGraw-

Hill.

5. Tipton KD, Rasmussen BB, Miller SL et al. (1999) Postexercise net protein synthesis in

human muscle from orally administrated amino acids. Am J Physiol Endocrinol Metab,

276:E628-E634.

6. Tipton KD, Rasmussen BB, Miller SL et al. (2001) Timing of amino acid-carbohydrate

ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol

Endocrinol Metab 281:E197-E206.

7. Tipton KD, Borsheim E, Wolf SE et al. (2003) Acute response of net muscle protein

balance reflects 24-h balance after exercise and amino acid ingestion. Am J Physiol

Encorinol Metab 284:E76-E89.

Anssi Manninen is Finnish exercise physiologist specialising in sports nutrition

and ergogenic aids and has consulted elite athletes in all sports. Questions to

Anssi can be directed to [email protected]