Casein and whey are two of the most popular proteins on the market today. They are natural, high quality sources of protein derived from milk, and each have unique properties and benefits that make them gold standards for anyone trying to gain muscle or support their dietary protein intake.
Casein, accounting for 80% of the total, is the main protein present in milk. It is available in two forms – Insoluble and Soluble casein.
The best known and most widely used form of casein is the insoluble form, known as Micellar casein. This form of casein is made up of insoluble structures called micelles, which are composed of thousands of casein molecules arranged around an inner core of calcium ions. It is this structure that gives casein its unique properties.
After micellar casein is ingested, it reacts with the acid in the stomach and congeals into a large mass. This large mass is then broken down slowly over many hours. This slow breakdown provides the body with amino acids over a long period of time. Casein has famously been described as "The world's only anti-catabolic protein" and it is an ideal protein to take before bed, because the constant release of amino acids maintains a positive nitrogen balance during sleep, when muscle is built (1,3).
Micellar Casein is also very rich in calcium, which is essential for healthy bones and muscles.
Soluble casein, often described as "caseinate" on a product label, dissolves readily in water, and is absorbed into the body very quickly after ingestion. It is an excellent quality protein and is quite similar to whey (2).
Whey is the most popular protein supplement on the market. Like Casein, it is an excellent quality protein, rich in essential amino acids, and it has the highest bioavailability out of any protein, which means that more of the whey you ingest gets to the muscles and helps to build lean mass.
Whey is a very easily digested and rapidly absorbed protein, and it is the go to for those needing a quick protein hit (4). There are a variety of whey supplements on the market – Whey Protein Concentrate is a simple and cost effective preparation, Whey Protein Isolate is a higher quality, more refined product and Whey Protein Hydrolysate has been digested by a process called hydrolysis to produce smaller protein fragments that are absorbed almost instantly.
Studies have shown that whey is strongly anabolic. This is due to its rapid absorption, and also because whey is rich in BCAAs and Leucine, essential amino acids which stimulate the growth of new muscle. Supplementation with whey has been shown to increase both strength and muscle volume (3). Whey, like other proteins, is also known to assist weight loss through maintenance of muscle mass and producing feelings of fullness.
Casein or Whey?
Both! A fast acting protein that stimulates muscle growth like whey and a long-acting protein that prevents muscle breakdown like casein are perfect to use side-by-side to ensure that the body always has a source of protein. Nearly all of the most popular protein powders on the market, like MusclePharm's Combat, MuscleTech's Phase 8, and Gaspari MyoFusion, contain a blend that includes both casein and whey. Whey and casein are two of the best proteins around and make a great addition to anyone's supplement regime.
(1) Phillips (2011), Comparison of whey to caseinate. American Journal of Physiology. Endocrinology and Metabolism, 300: E610.
(2) Reitelseder (2011), Whey and casein labeled with l-[1-13C]leucine and muscle protein synthesis: effect of resistance exercise and protein ingestion. American Journal of Physiology. Endocrinology and Metabolism, 300: E231-E242
(3) Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrère B. Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci U S A. 1997 Dec 23;94(26):14930-5.
(4) Lacroix et al (2006), Compared with casein or total milk protein, digestion of milk soluble proteins is too rapid to sustain the anabolic postprandial amino acid requirement. Am J Clin Nutr, 84: 1070-1079.