by Chad Kerksick PhD November 29, 2012 6 min read
A number of factors dictate how your body responds to exercise training. Exercising factors include intensity, rest, frequency, multi-joint vs. single-joint exercises, exercise order and volume. On the nutrition side, factors such as age, training status/experience, carbohydrate availability, protein powder quality, nutrient timing and amino acid content all work together (or against each other) to cue the body whether to build or burn muscle. A recent study examined the impact of ingesting a recommended dose of whey protein or small doses of whey protein that were fortified with increased amounts of key amino acids (Churchward-Venne, Burd et al. 2012).
For those of you interested in this type of research, around 15 years ago scientific studies highlighted first that amino acid and protein turnover was altered in response to a single bout of resistance training (Biolo, Maggi et al. 1995). Follow-up research then told us that adding a healthy dose of branch chain amino acids can increase muscle protein synthesis (Biolo, Tipton et al. 1997). Some years after that, the science then started to highlight the importance of the essential amino acids; the amino acids you must get in your diet because our bodies lack the ability to produce them. The first of these studies simply told us that ingesting a large dose (40 grams) of the essential amino acids favorably increased the balance of muscle protein in the body (Tipton, Ferrando et al. 1999). However, when a 35 gram dose of carbohydrate was added to a much smaller dose of essential amino acids (6 grams), values of muscle protein synthesis were also found to maximally increased as well (Rasmussen, Tipton et al. 2000).
Research then focused more on the essential amino acids and a series of studies told us that nonessential amino acids weren’t required to maximally synthesize muscle proteins (Tipton, Gurkin et al. 1999; Borsheim, Tipton et al. 2002; Volpi, Kobayashi et al. 2003). From here, research began to explore more closely the specific impact of ingesting either the branched-chain amino acids (isoleucine, leucine and valine), in particular leucine, for their ability to stimulate positive changes in cellular activity. A number of research papers were subsequently published that highlighted the important effects of these amino acids (Nair and Short 2005; Rieu, Balage et al. 2006; Pasiakos, McClung et al. 2011).
The overall quality of a protein source is determined primarily by its amino acid content. Higher quality sources of protein have higher amounts of all of the essential amino acids. In this respect, no other source of protein routinely scores higher on evaluations of protein than whey protein. More so, isolate versions of whey protein or hydrolysates produced from whey isolate are viewed to be of the very highest quality. The term isolate means the final protein product is at least 90% protein by weight or only 10% of it is carbohydrate or fat. Hydrolysates are produced either by exposing the product to acid or enzymes to further break up the protein chain to yield a higher percentage of small peptides that can more easily be taken up into the various tissues of the body.
In essence, people are left with decisions between consuming ideal amounts of whey protein, leucine as well as the remainder of the essential amino acids. While consuming a minimum of 25 grams or so of a whey protein isolate delivers the needed amounts of cell-activating amino acids, sometimes you find yourself at a place where you need to feed your body, but you can’t. Maybe you are on the road and can’t mix your shake, at work in meetings or you don’t want to clean up your shaker cup. All of these reasons highlight why scientists might try to look for unique combinations of proteins and amino acids. In fact, another reason is the overall bulk or volume of liquid for some populations (older individuals, smaller-framed folks and women) can leave them feeling uncomfortably full or bloated.
In this recent study, Canadian scientists divided 24 males into three groups and assessed the rate of muscle protein synthesis after they ingested different nutrient combinations with and without the presence of resistance exercise. The first group ingested a typical 25 gram dose of whey. A second group ingested only 6.25 grams of whey protein, but the protein was fortified with greater amounts of leucine to match the leucine amount provided in the first group. The third and final group ingested only 6.25 grams of whey protein, but the protein from this group contained added amounts of the essential amino acids (with the exception of leucine) as to deliver the same amount of the essential amino acids (except for leucine) as what was ingested in the group that ingested 25 grams of whey protein (group 1).
All supplements were ingested at rest and without any additional influence of resistance exercise, the ingestion of the two groups which contained leucine (groups 1 and 2) led to significant increases in blood levels of leucine. In addition, the increased leucine levels in these two groups were significantly greater than the blood levels of leucine found in group 3 (the group which didn’t consume any leucine). No surprises so far.
Regardless of whether resistance exercise was added or not, immediate changes (the first 3 hours after exercise and feeding) in muscle protein synthesis were actually similar in all three groups. In other words, if you know you are in super hurry and don’t have time to deal with making a shake and cleaning up the mess, simply delivering an adequate amount of leucine or the essential amino acids will adequately bridge the gap for up to three hours. NOTE: Don’t lose sight of the fact that ingesting a whey protein shake definitely suffices as well.
However, when these measurements were extended to 3 – 5 hours, only the group which ingested 25 grams of whey protein were able to sustain the increased levels of muscle protein synthesis. Therefore, if you know you are going to be unable to feed your muscles for an extended period you are better off getting a minimum of 25 grams whey protein shake. In closing, stimulating muscle protein synthesis takes a constant balance of a number of factors and timely delivery of the right nutrients can greatly impact these changes.
Biolo, G., S. P. Maggi, et al. (1995). “Increased rates of muscle protein turnover and amino acid transport after resistance exercise in humans.” Am J Physiol 268(3 Pt 1): E514-520.
Biolo, G., K. D. Tipton, et al. (1997). “An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein.” Am J Physiol 273(1 Pt 1): E122-129.
Borsheim, E., K. D. Tipton, et al. (2002). “Essential amino acids and muscle protein recovery from resistance exercise.” Am J Physiol Endocrinol Metab 283(4): E648-657.
Churchward-Venne, T. A., N. A. Burd, et al. (2012). “Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men.” The Journal of physiology.
Nair, K. S. and K. R. Short (2005). “Hormonal and signaling role of branched-chain amino acids.” J Nutr 135(6 Suppl): 1547S-1552S.
Pasiakos, S. M., H. L. McClung, et al. (2011). “Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis.” Am J Clin Nutr 94(3): 809-818.
Rasmussen, B. B., K. D. Tipton, et al. (2000). “An oral essential amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise.” J Appl Physiol 88(2): 386-392.
Rieu, I., M. Balage, et al. (2006). “Leucine supplementation improves muscle protein synthesis in elderly men independently of hyperaminoacidaemia.” The Journal of physiology 575(Pt 1): 305-315.
Tipton, K. D., A. A. Ferrando, et al. (1999). “Postexercise net protein synthesis in human muscle from orally administered amino acids.” Am J Physiol 276(4 Pt 1): E628-634.
Tipton, K. D., B. E. Gurkin, et al. (1999). “Nonessential amino acids are not necessary to stimulate net muscle protein synthesis in healthy volunteers.” J Nutr Biochem 10(2): 89-95.
Volpi, E., H. Kobayashi, et al. (2003). “Essential amino acids are primarily responsible for the amino acid stimulation of muscle protein anabolism in healthy elderly adults.” Am J Clin Nutr 78(2): 250-258.
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