Studies show, however, that older people who take in easily digested protein, such as whey or amino acids, can overcome the protein deficit and may prevent sarcopenia by preserving muscle. Adding weight training makes the increased protein intake even more effective. The active ingredients in both whey and amino acid mixtures are presumed to be essential amino acids, which are so named because they can’t be synthesized in the body and must be obtained from food. Depending on which source you consult, either eight or nine amino acids are deemed essential in adult nutrition. The remaining aminos aren’t labeled “essential” not because they are unimportant but rather because the body can synthesize them. The anabolic effect of taking in essential amino acids is so potent that a mere six grams are enough to double the rate of protein synthesis. Of the essential amino acids, the branched-chain amino leucine is considered the most potent in that regard. Indeed, several studies have shown that leucine alone activates a number of reactions that form the basis of protein synthesis in the body.
One study compared intake of whey protein to essential aminos in older people who got 15 grams of each. The essential aminos more than doubled the protein balance compared to the whey intake, indicating that essential aminos are the active factors in the anabolic impact of protein. It’s as if essential amino acids are all older people need to correct protein problems.
In a new study1 15 people aged 60 to 85 were randomly assigned to take 1) 15 grams of whey protein, 2) 6.72 grams of EAA or 3) 7.57 grams of nonessential amino acids.1 In other words, the subjects got amino acids either as a whole protein source—whey—or as free amino acids, both essential and nonessential. Protein synthesis was measured by monitoring the activity of phenylalanine, an amino acid incorporated into muscle. The phenylalanine balance over a 3.5 hour period increased in the whey group but not in the essential or nonessential amino groups. How could that be, when previous studies showed that essential amino acids are superior to whey in causing anabolic effects in older people?
The answer lies in dosage. In the previous study 15 grams of essential amino acids were directly compared to 15 grams of whey. In the more recent study 15 grams of whey were compared to only 6.72 grams of essential aminos. Due to the blunted effects of protein metabolism in older people, it takes a greater amount of essential aminos, particularly leucine, to yield anabolic effects. Supplying large amounts of leucine can lead to protein synthesis in the elderly that is similar to that in younger people. Confusing the issue is that since whey contains 50 percent essential aminos, getting the same amount as straight essential aminos should have led to similar effects, yet the whey proved superior.
Whey, however, also contains other aminos involved in protein synthesis, such as cysteine, that may explain why the whey proved superior to essential aminos in the study. The whey also brought on a greater insulin response than the aminos, likely because the whey provided twice the level of aminos, some of which spur insulin release. The relevance here is that insulin potently helps along muscle protein synthesis only in the presence of a large amount of amino acids. The ones present in whey but not in the essential aminos mixture, such as arginine and aspartic acid, are potent partners in insulin release. The authors suggest that a combination of essential and nonessential aminos stimulates insulin. Thus, the study shows that whey exerts more potent muscle protein synthesis than free amino acids because it more potently stimulates insulin.
Leucine deficiency can be remedied with supplements, but a study revealed another way to deal with that problem.2 A negative by-product of aging is an increase in oxidative damage caused by decreased activity of built-in body antioxidants, such as superoxide dismutase, catalase and glutathione. Lack of antioxidant protection enables free radicals to wreak oxidative havoc in the body. That eventually results in a host of degenerative diseases related to the aging process. Oxidative damage can also interfere with the activity of body proteins, including protein-based hormones, such as insulin. A hallmark of out-of-control oxidation is increased tissue inflammation, which is the underlying cause of diseases linked to aging.
It turns out that oxidation-related inflammation is responsible for the lack of anabolic response to leucine in older people. In the new study, which lasted seven weeks, old rats with defective leucine metabolism were given a mixture of dietary antioxidants containing rutin (a common bioflavonoid found in fruit), vitamin E, vitamin A, zinc and selenium. The refractory leucine metabolism in the old rats was completely reversed, probably because of the antioxidant supplements. The effect was independent of leucine intake, meaning that it worked with normal leucine intake. Other studies have shown that antioxidant supplementation in older animals seems to help preserve muscle, and the effect on leucine metabolism may explain that frequently observed reaction.
It may be that in humans antioxidants work synergistically with increased and regular intake of protein to preserve muscle mass with the passing years.
References
1 Katsanos, C.S., et al. (2008). Whey protein ingestion in elderly persons results in greater muscle protein accrual than ingestion of its constituent essential amino acid content. Nut Res. 28:651-658.2 Marzini, B., et al. (2008). Antioxidant supplementation restores defective leucine stimulation of protein synthesis in skeletal muscle from old rats. J Nutr. 138:2205-2211.
©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
