Whey protein is a common dietary supplement for increasing muscle mass and reducing the risk of obesity, type II diabetes, high blood pressure, inflammation, and oxidative stress. It is typically isolated from acidic liquid (whey) created during the cheese making process, making it a cheap and easily accessed commercial supplement. Whey protein is rapidly and effectively digested since it is water soluble, and it provides a high content of balanced essential amino acids (EAAs) with high dose of leucine. Whey protein stimulates muscle protein synthesis (MPS) more than other proteins such as casein and soy proteins, both at rest and following exercise in young and older adults (1).
Why whey?
- Fast-digested protein: Whey is acid-soluble so that it exits the stomach rapidly and increases blood AAs immediately after consumption. This feature is important since high level of blood AAs associated with increased insulin level is essential to enhance MPS and gain muscle mass effectively. Casein protein is a slow-digested protein, which clots in the stomach and slowly exits to the small intestine. Thus the release of AAS into the bloodstream is not quick enough to catch up with the level of insulin.
- Complete protein: Whey protein contains all essential amino acids (EAAs). Soy protein also contain all EAAs but is deficient in methionine and lysine compared to milk protein.
- Leucine rich protein: Leucine, one of branched-chain AAs (BCAAs), is an insulin stimulator and essential for MPS in muscle tissues. Whey protein has more leucine and BCAAs than others including soy and casein proteins.
- Efficient protein: Whey is rapidly digested and releases BCAAs, which are delivered quickly to muscle tissues. Casein protein is also rich in BCAAs but it is slow-digested protein. Bioavailability of soy protein is lower than dairy protein because the presence of endogenous inhibitors of digestive enzymes (e.g., trypsin inhibitors), poor digestibility of raw soybean and the high ratio of degradation into urea (2). In addition, soy protein is less efficient for MPS due to lower contents of BCAAs than dairy protein.
Types of whey protein
There are four major forms of whey, concentrate (WPC), isolate (WPI), hydrolysate (WPH) and native whey proteins. WPC is a course form, which contains ~29%–89% of protein and rest of it includes fat, cholesterol and lactose. WPI is the purest form containing more than 90% of protein with no fat and lactose. WPH is a digested-whey for the purpose of easier metabolizing. Native whey protein is extracted from skim milk, not a byproduct of cheese production.
Lacto-vegetarian and Kosher options
Since most of whey proteins are separated from a byproduct of cheese productions, animal-rennet is probably involved in the process. Lacto-vegetarians and Jewish people need to choose the native whey and whey protein products with kosher or halal mark that are free from animal-rennet.
How much whey protein after exercise? (1, 2)
Numerous studies show MPS is maximally stimulated when 20g of high quality protein containing ~10g of EAAs and 1.7-2.4g of leucine. A 25g of WPI (90% of protein) contains 22.5g of protein including 3g of leucine, 12.4g of EAAs and 5.6g of BAAs. If you want to blend with 1 cup of milk, which contains 8g of protein with similar ratio of AAs, you can reduce the powder significantly.
References
- Devries MC and Phillips SM (2015). Supplemental Protein in Support of Muscle Mass and Health: Advantage Whey. J Food Sci. 2015 Mar;80 Suppl 1:A8-A15
- Luiking, YC et al (2005). Casein and Soy Protein Meals Differentially Affect Whole-Body and Splanchnic Protein Metabolism in Healthy Humans. J Nutr. 2005