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What is whey?

Medically reviewed by Carmen Pope, BPharm. Last updated on May 3, 2023.

Official answer


Milk can be easily separated into two major components: whey (the liquid portion), and curds (the rest that is left behind).

Whey contains proteins, vitamins, fats, carbohydrates, and minerals. Whey has been of interest to athletes because it contains all the essential amino acids needed for muscle growth and repair. Whey protein exists in three major forms:

  • Whey protein concentrate (WPC): contains low amounts of fat and carbohydrates, and the protein percentage depends on how concentrated the product is (ranges from 30-90%)
  • Whey protein isolate (WPI): further processing occurs to remove all the fat and lactose. The protein percentage is usually around 90%
  • Whey protein hydrolysate (WPH): further processed to improve digestibility and reduce allergen potential.

The choice of whey protein comes down to budget, allergies, and reasons for supplementation.

Which whey protein is better?

Whey protein concentrate (WPC) contains significant amounts of lactose, so should be avoided by anyone with lactose intolerance. However, because it is the least processed of all whey forms, it theoretically has health advantages over the isolate and hydrolysate forms because processing can denature peptides in the whey making them less biologically active, although this appears not to affect muscle-building properties. More expensive methods of processing, such as micro-filtration, yield whey isolates with more potential biological activity.

The most easily digestible, but least active, peptides are found in whey protein hydrolysate. Both isolates and hydrolysates are popular post-workout supplements as they contain a higher amount of protein per serving than WPC, fewer calories (which may be a concern for those watching their weight), and are more readily absorbed into the bloodstream. However, they are more expensive, and processing may mean health benefits are less. In addition, their increased absorption rate may cause a more profound insulin response which may not be ideal for people trying to control insulin fluctuations.

Related questions

What are the benefits of whey?

Whey protein has been extensively studied and some trials report enhanced muscle growth and improved recovery; however, not all studies have found positive effects. Possibly effectiveness depends on the timing of supplementation, the athlete's pre-existing nutritional state, and the volume, intensity, and frequency of training. One study found no difference in recovery or performance between top cyclists at a training camp supplemented with both protein and carbohydrates compared with those supplemented with carbohydrates alone.

Some experts still favor supplementation with whole foods, preferring a glass of milk, which contains both whey and casein (beneficial at preventing muscle breakdown) to whey protein alone.

  • Davies RW, Carson BP, Jakeman PM. The Effect of Whey Protein Supplementation on the Temporal Recovery of Muscle Function Following Resistance Training: A Systematic Review and Meta-Analysis. Nutrients. 2018;10(2):221. Published 2018 Feb 16. doi:10.3390/nu10020221
  • Peeling P, Binnie MJ, Goods PSR, Sim M, Burke LM. Evidence-Based Supplements for the Enhancement of Athletic Performance. Int J Sport Nutr Exerc Metab. 2018;28(2):178-187. doi:10.1123/ijsnem.2017-0343
  • Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439-455. doi:10.1136/bjsports-2018-099027
  • Peeling P, Castell LM, Derave W, de Hon O, Burke LM. Sports Foods and Dietary Supplements for Optimal Function and Performance Enhancement in Track-and-Field Athletes. Int J Sport Nutr Exerc Metab. 2019;29(2):198-209. doi:10.1123/ijsnem.2018-0271

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