WHAT IS WHEY?
Whey is the compound that remains after milk coagulates during cheese production. It has been defined as a 5% solution of the milk sugar, lactose, in water, combined with some minerals and lactalbumin (which is the protein found in the milk of mammals). Whey protein is the combination of certain types of proteins (globular proteins) that have been isolated from whey. These proteins include β-lactoglobulin, α-lactalbumin, and serum albumin. Whey has a high biologic value, meaning, it can be incorporated into the body to make more proteins (1).
WHY HAS WHEY PROTEIN BECOME POPULAR?
Whey protein has become popular, especially among weightlifters and bodybuilders, because it is thought to increase lean muscle mass at a faster rate than other proteins or amino acid supplements. A great deal of research has been conducted on whey protein. A review of some of the research will be discussed in this article.
WHEY PROTEIN AND LEAN MUSCLE MASS IN HEALTHY INDIVIDUALS
Candow et al. (2) evaluated changes in lean muscle mass, strength, and myofibrillar (muscle contractile) protein breakdown in 27 untrained healthy participants (18 women, 9 men, 18-35 years of age) who were placed on a supervised resistance training program. They were randomly assigned, in a double-blind manner, to one of three groups: whey protein supplement group (1.2 g/kg of body mass of whey protein plus 0.3 g/kg of body mass of sucrose powder), soy protein supplement group (1.2 g/kg of body mass of soy protein plus 0.3 g/kg of body mass of sucrose powder), or placebo (1.2 g/kg of body mass of maltodextrine plus 0.3 g/kg of body mass of sucrose powder). They found that lean muscle mass and strength were increased more than the placebo for both protein sources.
In a more recently published study, Hulmi et al. (5) evaluated whey protein, compared with a placebo, after 21 weeks of resistance training, conducted two times per week. This was an invasive study whereby the researchers took muscle biopsies to evaluate true evidence of increased muscle mass and also to evaluate protein expression (a marker of cellular protein synthesis) in the muscle. They found that resistance training alone increased the expression of a muscle-building response; however, they stated that whey protein may increase and prolong the response.
In another study on healthy individuals, Cribb and colleagues (3) assessed the effects of different proteins on muscle mass. They compared, in a double-blind fashion, hydrolyzed whey protein isolate with casein protein (another milk protein) on strength and body composition in 13 male recreational bodybuilders during a 10-week supervised resistance training program. The participants were given 1.5 g/kg of body weight per day of the specific protein supplement. They measured body composition by dual-energy X-ray absorptiometry, one of the criterion standards of measuring body composition. They found that whey protein significantly improved lean muscle mass, decreased fat mass, and increased strength compared with casein. These various studies in healthy individuals seem to suggest that whey protein may enhance muscle mass and strength when evaluated from both clinical and molecular standpoints.
Although it seems that whey protein may enhance muscle mass, one research group reported that the type of protein did not matter; it was simply the increase in protein intake that increased lean muscle mass. That is an important distinction, especially for individuals who may not like whey protein or who may not consume animal products. These studies were conducted in healthy participants, however. Does whey have the same effect in other populations?
WHEY PROTEIN SUPPLEMENTATION IN OBESE INDIVIDUALS
In another randomized controlled trial, Denysschen et al. (4) evaluated if whey protein intake would result in weight loss in 158 obese individuals (body mass index [BMI], 30-42 kg/m2). Although participants in both groups lost weight because of the energy deficit of 500 kcal in their diet, those who took the whey protein supplement lost significantly more body fat and preserved more lean body mass than the control group.
If whey protein helps with weight loss, might it also help with reducing lipid levels? It was found that body weight, body composition, strength, and lipid levels were all improved in men with hyperlipidemia whether they took whey protein supplementation, soy protein supplementation, or a placebo (4).
WHEY PROTEIN SUPPLEMENTATION IN OLDER INDIVIDUALS
Sarcopenia is the loss of skeletal muscle associated with aging. Perhaps whey protein supplementation may decrease muscle mass loss in older individuals. Katsanos and colleagues (6) reported that 15 g/day of whey protein resulted in greater protein muscle accrual compared with those of essential amino acids or nonessential amino acids in 15 older participants. These data could have implications for preservation of muscle mass in older persons; however, more research is still required.
Whey protein seems to be a good protein supplement for preserving muscle mass and, perhaps, for assisting with weight loss. Although most of the studies presented in this issue's Nutritionist's View showed positive results, not all of the studies did. Nonetheless, these data may help with our understanding of what protein works best for muscle mass preservation in people of all ages and fitness levels.
2. Candow DG, Burke NC, Smith-Palmer T, Burke DG. Effect of whey and soy protein supplementation combined with resistance training in young adults. Int J Sport Nutr Exerc Metab
3. Cribb PJ, Williams AD, Carey MF, Hayes A. The effect of whey isolate and resistance training on strength, body composition, and plasma glutamine. Int J Sport Nutr Exerc Metab
4. Denysschen CA, Burton HW, Horvath PJ, Leddy JJ, Browne RW. Resistance training with soy vs whey protein supplements in hyperlipidemic males. J Int Soc Sports Nutr
5. Hulmi JJ, Tannerstedt J, Selanne H, Kainulainen H, Kovanen V, Mero AA. Resistance exercise with whey protein ingestion affects mTOR signaling pathway and myostatin in men. J Appl Physiol
© 2009 American College of Sports Medicine.
6. Katsanos CS, Chinkes DL, Paddon-Jones D, Zhang XJ, Aarsland A, Wolfe RR. Whey protein ingestion in elderly persons results in greater muscle protein accrual than ingestion of its constituent essential amino acid content. Nutr Res