Whey(Fast) VS Casein(Slow) Protein

by Medicate. Meditate. Educate.

Whey(fast) Protein VS Casein(slow) Protein

Protein powder is a staple for anyone trying to put on muscle. I know that some of you have giant tubs of protein powder that most likely is the size of my bind. (Good for you! Keep eating!) I hear it all the time in the gym, class and everywhere around us about Protein powder. I thought I would get on writing and start simple using the very famous K.I.S.S method.

Keep It Simple Stupid!

If you walk into most supplement stores you’ll find more brands, flavours and types of protein than you can imagine. It almost like walking into Willy Wonka`s chocolate factory.  Of course, most people go with a powder that they can tolerate the taste of; since many brands taste remarkably bad however, which kind is best?

What is protein powder?

For starters, protein powder is simply processed – that is right I hate arguing with people about this. Processed protein powder is dried protein that’s convenient and portable. (Will Have a post on Everything you need to know about protein powders)

In 2004, dairy-based proteins were the major source of protein in sports supplements — about three-quarters. Soy proteins made up most of the rest. In recent years, plant based protein powders have become more common and this is due to people trying to get as natural as possible (still processed) or have a food tolerance and need other alternatives or simple they are well informed about the biochemistry and bio-physiology of their body.  However, dairy proteins like whey and casein still make up most of the protein supplements on the market and it is the most commonly bought.

Whey protein powder — the most common form of dairy-based protein powders — is the liquid by-product of making cheese. Casein, on the other hand, is from the solid part of skim milk when treated with acid (like lemon juice- Got any lemons?). Casein is what you get when milk curdles —  it’s the curd part.

Dairy proteins (as well as egg protein) are considered complete proteins, since they have all essential amino acids in sufficient amounts. A few plant proteins, like hemp, are also complete, but have a lower total amount of protein. However once processed it can lose some or all of its amino acid content due to the process and heat that will change the chemical structure.

Whey versus casein

Whey and casein has been a staple for bodybuilders for years. Each protein has unique characteristics. But which is better?  Well deciding which protein is better depends on the purpose of the protein.

In terms of similarities, both are complete proteins and both have identical Protein Digestibility Corrected Amino Acid Scores (PCDAAs; 1.00) [2].  So, to determine which is better, we have to dig deeper – This is how it always is. First glance it looks the same but if we go a little deeper we will see sufficient differences.

In terms of differences, whey protein has more leucine(check my previous articles on this kick ass amino acid – Warning builds muscle), while casein is higher in glutamine (Whey is also absorbed much more quickly than casein.

Leucine and glutamine in muscle protein synthesis

Leucine, uniquely, activates skeletal muscle protein synthesis through a series of molecular biology interactions similar to dominos, called the mammalian target of rapamycin (mTOR) pathway. Since leucine is a key amino acid for activating protein synthesis, and since whey has more leucine, it’s a good choice for building muscle mass. (Seriously read my previously articles)

Glutamine is also important in muscle protein synthesis. After exercise, glutamine is depleted in blood plasma and muscle. More muscle glutamine is directly correlated to higher muscle protein synthesis. Glutamine supplementation leads to more growth hormone, which has anabolic affects on muscle.

Absorption rates

The other difference between whey protein and casein protein is how fast the protein is absorbed, and for how long.

Researchers measure blood amino acids to figure out rate of protein absorption. Drinking whey protein causes increases in blood amino acids levels in under an hour, with peak levels at just under 90 minutes. Casein takes longer to increase blood amino acids, but lasts longer, with elevated levels lasting over 300 minutes.


High peak levels of blood leucine and amino acids cause more muscle protein synthesis than blunted but longer elevated levels of blood leucine and amino acids.  So what does that mean for you?

If muscle building is your primary goal, try drinking a fast-digesting protein drink (with at least 25 grams of protein) within 15 minutes of exercising. If you really want to experiment you could drink a second fast-digesting protein drink 2 or 3 hours after the first. It could be that a second drink after blood amino acids are back to normal would cause more muscle protein synthesis by causing a second peak in blood leucine. – I have been eating food post workout and I am going on Protein powders just for post workout reasons as eating a meal is harder that sipping a shake aka you do not feel hungry and it feels like choking eating food after a workout.

Now, if you can’t digest dairy, opt for lean proteins from whole foods, like eggs, seafood, or lean meats, and keep your post-workout fat intake low and carb intake high to speed absorption. Have some lean protein an hour or two before training as well, so that there are amino acids already starting to float around. If possible, eat your biggest protein meal of the day as soon as possible after heavy training.  Even throw in some BCAA (branched chain amino acids) (Check my previous article on this) during training.

Drinking 25 grams of fast-digesting whey protein, all at once and immediately after exercise, increases muscle protein synthesis more than drinking 25 grams of whey protein over 3 hours after exercise.


  • NBJ’s Sports Nutrition and Weight Loss Report 2007-2008. Nutrition Business Journal. Boulder CO. New Hope Natural Media, January 2008.
  • Paul GL. The rationale for consuming protein blends in sports nutrition. J Am Coll Nutr. 2009 Aug;28 Suppl:464S-472S. Review.
  • 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.