It can be a bit confusing trying to work whether you want to go with Whey protein or Casein protein powders - especially considering there can be so many.
Firstly however you need to realise that although there are differences between these products, it is not going to be a major disaster and a cause for anguish, if you happen to use one product instead of another. It is difficult to make any 'cut and dried' rules because everyone's body is different and what may work well for one person may not work as well for some someone else. It's basically a case of - do whatever works for you!
There has however, been some research done in these areas that may help give us some concrete information to use in making our decisions. Whey Protein and Casein Protein are the two most common ingredients of protein powders in the marketplace. If you understand something about the way both of these extracts work then you can readily assess what a particular product may do for you. Boirie et al 1997 decided to investigate the effects of ingesting these two different types of milk protein extracts on post meal blood amino acid levels and muscle gain or loss.
They noticed that post meal blood amino acid levels differ a lot depending on the mode of administration of a dietary protein; a single protein meal results in an acute but transient peak of amino acids whereas the same amount of the same protein given in a continuous manner over a number of smaller meals, which mimics a slow absorption, induces a smaller but prolonged increase. (Amino acids are potent modulators of protein synthesis, breakdown, and oxidation, so such different patterns of postprandial amino acidemia might well result in different postprandial protein kinetics and gains). Of interest, whole body leucine balance, an index of protein deposition, was shown previously to differ by El-Khoury et al 1995 under these two circumstances.
Therefore, Boirie's hypothesis was that the speed of absorption by the gut of amino acids derived from dietary proteins might affect whole body protein synthesis, breakdown, and oxidation, which in turn control protein deposition. To test this hypothesis, they compared those parameters, assessed by leucine kinetics, after ingestion of a single meal containing either whey protein concentrate (WPC) or casein (CAS), taken as paradigms for "fast" and "slow" proteins, respectively. Indeed, WPC is a soluble protein whereas CAS clots into the stomach, which delays its gastric emptying and thus probably results in a slower release of amino acids. Speed of amino acid absorption was directly assessed by using a newly developed tracer, ie., milk protein fractions intrinsically labelled with L-[1-13C]leucine . Leucine kinetics were modelized by using non-steady-state equations as recently described research by Boirie et al in 1996.
The two protein meals were matched for leucine content but were not isonitrogenous, and amino acid intake was higher with CAS. (The researchers gave the subjects 30g of Whey Protein and 40 g of Casein Protein). Despite this higher amino acid intake, amino acid concentrations increased less with CAS than with WP at 100 min. By contrast, at 300 min, most amino acids remained at higher concentrations with CAS whereas they returned to basal levels with WPC.
After WPC ingestion, the plasma appearance of dietary amino acids is fast, high, and transient. This amino acid pattern is associated with an increased protein synthesis and oxidation and no change in protein breakdown. By contrast, the plasma appearance of dietary amino acids after a CAS meal is slower, lower, and prolonged with a different whole body metabolic response: Protein synthesis slightly increases, oxidation is moderately stimulated, but protein breakdown is markedly inhibited. The latter metabolic profile results in a better leucine balance.
WPC induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia, probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not after WPC ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 ? 91 ?mol?kg-1) than with WP (373 ? 56 ?mol?kg-1). Leucine intake was identical in both meals (380 ?mol?kg-1). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP (P
This study demonstrates that dietary amino acid absorption is faster with WPC than with CAS. Their methodology did not allow identification of the rate limiting step(s) that might be gastric emptying and/or luminal hydrolysis and/or amino acid mucosal absorption. It is very likely, however, that a slower gastric emptying was mostly responsible for the slower appearance of amino acids into the plasma. Indeed, CAS clots into the stomach whereas WPC is rapidly emptied from the stomach into the duodenum . Mahe et al 1996 investigated the flow rates across the intestine of both Whey Protein and Casein Protein and found that the jejunal flow rate of 400ml of liquid whey protein was 7.27ml/min and peaked at the 0-20mins range and that of a casein solution 5.69 ml/min peaked at the 20-40 min period. This proved that whey does absorb faster.
Thus, after WPC ingestion, large amounts of dietary amino acids flood the small body pool
in a short time, resulting in a dramatic increase in amino acid concentrations. By contrast, with CAS, plasma amino acid concentrations are lower, resulting in a lower oxidation and in a lesser increase of protein synthesis but also in an inhibition of protein breakdown.
Their results demonstrated that amino acids derived from CAS are indeed slowly released from the gut and that slow and fast proteins differently modulate postprandial changes of whole body protein synthesis, breakdown, oxidation, and deposition. The slowly absorbed CAS promotes postprandial protein deposition by an inhibition of protein breakdown without excessive increase in amino acid concentration; by contrast, a fast dietary protein stimulates protein synthesis but also oxidation.
The experimenters commented that the impact of amino acid absorption speed on protein metabolism is true when proteins are given alone, but as for carbohydrate, this might be blunted in more complex meals that could affect gastric emptying (lipids) and/or insulin response (carbohydrate); thus, further studies are needed to confirm the specific roles of non-protein substrates on whole body protein metabolism. This means that unless we are eating a meal based purely on protein, we have to take into account the effects that carbohydrates and fats can have on protein metabolism. We must also realise that this study was based on the ingestion of a single meal of liquid protein.
Based on these studies we can however conclude that if you are looking for fast delivery of aminos and proteins into your tissues to increase protein synthesis and recovery, you should use a Whey Protein such as WPC 85+, or WPI Ionised Whey Protein. Basically it goes in with a rush does its job, but its energy is expended. If you are looking to inhibit protein and muscle breakdown you will be better to use the 92% protein which has Calcium Caseinate in it, it 'keeps on keeping on' and breaks down slowly giving your muscles a 'trickle feed' much like some of those garden watering devices.
This applies for a single protein meal, but you can still get around this one if you want to keep using your Whey Protein shake at regular intervals every 2 hrs, you will just have to remember to keep 'topping it up'. You could on the other hand, get very clever and take a WPC or WPI after training and then use your 92% during the day or better still before bed.
Article source: Musashi UK
