Download Pre- and Post-Exercise Amino Acid Supplementation

Nutrition Performance
By Anssi Manninen
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
Strength-trained, gain muscle
mass
Endurance-trained
Weight-restricted
1.2-1.4
1.6-1.8
1.2-1.4
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, 14:251258, 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 23:528536, 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/McGrawHill.
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]
.