The latest on whey protein

by Jeff S. Volek, Ph.D., R.D.

Whey protein is a high quality protein that, together with casein, are the major proteins in milk. In prior articles, I’ve written about the growing body of research showing the benefits of whey protein for athletes.

Whey protein is digested quickly, resulting in a more rapid increase in plasma amino acids (compared to casein), and it rapidly stimulates muscle protein synthesis. Whey also augments adaptations to resistance training as shown by increases in muscle strength and enhanced lean body mass. These effects may be due to the high degree of branched-chain amino acids in whey, particularly leucine.

Leucine is a hot topic among researchers because it has been shown to have very different properties than other amino acids. Most important, leucine directly stimulates the early cellular process involved in protein synthesis called initiation translation.1 Whey protein contains much more leucine than other protein sources.

Whey Before or After Exercise?

The timing of whey protein intake has been shown to be an important variable for maximizing its effects. Prior studies indicated that when free-form amino acids plus carbohydrate were taken before resistance exercise, it resulted in a more anabolic (muscle building) response compared to consumption after resistance exercise. This was an exciting finding because it showed the value of ingesting amino acids before a workout for maximizing protein synthesis. However, no work had validated these findings using an intact whey protein (not free-form).

A recently published study in the American Journal of Physiology examined whether the timing of whey protein was important in terms of promoting anabolism.2 Healthy subjects were placed in a group that received 20 grams of whey protein immediately before a bout of resistance exercise, or a group that received the same whey protein immediately after. The anabolic response (muscle protein balance) was increased in both groups whether taken before or after exercise. Some subjects had a significantly greater anabolic response when whey protein was consumed before exercise, but the average responses were similar.

The researchers suggested a better time to ingest whey protein before exercise might be 30 to 45 minutes prior to exercise in order to allow for the digestion and absorption of the amino acids. The logical conclusion from this research is to consume whey protein at both time points (both pre and post-exercise) for maximizing protein synthesis and protein balance.

Whey Augments Muscle Size, Strength

Ingesting whey protein before and after workouts definitely drives up protein synthesis. But the real question is whether this leads to better muscle and strength gains.

Australian researchers addressed this question in a recent study that compared the use of whey isolate to casein protein by bodybuilders.3 Two groups supplemented their diets with 1.5 grams per kilogram body weight per day of either a whey or casein supplement while performing their normal resistance training for 10 weeks.

As expected, the whey group had a greater increase in lean body mass (11 lbs.) compared to the casein group (1.8 lbs.). In addition, the whey group lost more fat (-3.3 lbs.) compared to the casein group (-0.4 lbs.). The greater increases in lean body mass translated into greater strength gains over the 10 weeks in the whey group.

Whey Protein and Immune Health

Several studies have shown other important physiologic outcomes likely mediated by the unique peptides in whey.

Whey is a rich source of cysteine, the rate-limiting amino acid for synthesis of the potent antioxidant glutathione. Whey protein supplementation increases glutathione levels and protects against oxidative damage.4,5

Whey contains immunoglobulins and is rich in the amino acid glutamine. Both of these substances are important for a healthy immune system. Other peptides with immune-enhancing properties that have been isolated from whey include lactoferrin, lactoglobulin and lactalbumin.

Whey Protein and Weight Loss

In addition to the benefits whey protein has on strength and muscle building, whey also has positive effects on weight loss.

In a preliminary study, 90 overweight men and women were assigned to one of three groups for 6 months in which they took: 1) 60 grams of whey protein per day, 2) 60 grams of soy protein per day, or 3) 60 grams of carbohydrate per day.6 These supplements were simply added to the participants’ normal diet and no change was made to their exercise habits. Body composition and body weight were measured weekly until the end of the study.

After six months, the group who consumed the whey protein daily lost significantly more weight and 5 more pounds of body fat than the group who consumed the carbohydrate supplement. Also, the whey protein group had the lowest waist circumference of all three groups after the study period.

The soy group lost weight as well, but not quite as much as the whey protein group.

Thus, compared to added calories from carbohydrate, added calories from whey protein can decrease body weight and body fat in overweight men and women.

Whey has a myriad of benefits

The benefits of whey for athletes and those seeking general health continue to be substantiated in current studies. Whey represents a very efficient way to increase muscle gains without adding unnecessary calories and can even be used to enhance weight loss. In future issues, I’ll continue to bring you the latest research on therapeutic applications of whey protein.


1. Kimball SR, Farrell PA, Jefferson LS: Invited Review: Role of insulin in translational control of protein synthesis in skeletal muscle by amino acids or exercise. J Appl Physiol 2002, 93(3):1168-1180.

2. Tipton KD, Elliott TA, Cree MG, Aarsland AA, Sanford AP, Wolfe RR: Stimulation of net muscle protein synthesis by whey protein ingestion before and after exercise. Am J Physiol Endocrinol Metab 2007, 292(1):E71-76.

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 2006, 16(5):494-509.

4. Grey V, Mohammed SR, Smountas AA, Bahlool R, Lands LC: Improved glutathione status in young adult patients with cystic fibrosis supplemented with whey protein. J Cyst Fibros 2003, 2(4):195-198.

5. Micke P, Beeh KM, Buhl R: Effects of long-term supplementation with whey proteins on plasma glutathione levels of HIV-infected patients. Eur J Nutr 2002, 41(1):12-18.

6. D.J. Baer, K.S. Stote, B.A. Clevidence, G.K. Harris, D.R. Paul and W.V. Rumpler. Whey protein decreases body weight and fat in supplemented overweight men and women. #267.6, Experimental Biology, San Francisco, CA, April, 2006.



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