#1 - Digestion and Absorption Rate
One of the main differences between casein and whey protein is how quickly they digest. Whey protein digests quickly. Casein, slowly.
Researchers can observe this difference by measuring the amount of amino acids in the blood after consumption. Whey increases blood amino acids in under an hour and peaks at about 90 minutes. Casein, on the other hand, takes longer to increase blood amino acid levels but can last more than 2 hours.
So, which is better?
Well, it depends what you're looking for. However, when we're talking about muscle growth, the evidence speaks volumes. Notice what one group of researchers from McMaster University did to study how each amino acid affects protein synthesis. They gave a group of healthy men whey protein either as a BOLUS (a single dose of 25 grams) or a PULSE (ten 2.5 gram shots of protein every 20 minutes) to mimic the more slowly digested casein protein. They took note of how the protein synthesized during rest and after exercise.
What did they find?
The large dose (meant to represent whey) was more effective than the small, repeated, pulsed doses that mimic casein at synthesizing muscle protein. The large dose elevated blood levels of essential amino acids more than the pulsed shots. According to the published study, these great results from the BOLUS of whey is attributed to the fact that a rapid rise in amino acid concentrations, especially of leucine, activates the protein synthesis pathways. This is especially efficient right after an intense bout of resistance exercise.
#2 -Leucine Content
Whey has higher levels of one of the most potent amino acids - leucine. There are about 2.5 grams of this branched chain amino acid in every 23 grams of whey protein isolate.
What makes leucine indispensable, potent, and unique? Like all other amino acids, it does contribute to the building blocks used to assemble proteins. Leucine, however, also serves a second role in skeletal muscle. It serves as a nutrient signal that starts the process of muscle protein synthesis. Leucine works together with insulin and other anabolic hormones to activate different processes involved in building protein.
In one interesting study, a group of individuals were given drinks enriched with either 3.5 or 1.87 grams of leucine during two bouts of cycling. Muscle protein synthesis was 33% greater after 3.5g of leucine than the 1.87 gram dose. Also, there was less whole-body protein breakdown.
Clearly, when it comes to muscle-building, leucine content is a critical factor for determing quality. Your muscles need about 2.5-3.0 grams of leucine to maximize muscle protein synthesis. Whey protein isolate is a rich source and easy way to cover your bases.
Bottom line? To get the most benefit from your EnergyFirst whey protein isolate powder 1) take it all at once, 2) take at least 25 grams of fast-digesting whey protein, 3) consume it immediately after your workout.
1. Am J Clin Nutr. 2011 Sep;94(3):795-803. doi: 10.3945/ajcn.111.013722. Epub 2011 Jul 27
2. Am J Clin Nutr 2011;94:809–18
3. Nutr Metab (Lond). 2012 Jul 20;9(1):67. doi: 10.1186/1743-7075-9-67.
4. Norton LE et al. Nutr Metab. 2012. 20;9(1):67.