Whey is a natural byproduct of the cheese-making process (from milk). Approximately 20 percent of the protein found in milk is whey protein. Whey is rich in branch chain amino acids, lactose, minerals, and vitamins and contains lactalbumin (similar to serum albumin) and traces of fat.
Whey protein has been shown to increase protein synthesis. Some studies have also indicated that whey contributes to immune function among others.
Whey has also shown powerful antioxidant effects as it enhances glutathione levels. Glutathione is a tri-peptide that contains one amino acid residue from each of the following: glutamic acid, cysteine, and glycine. Glutathione occurs widely in plant and animal tissues and plays a major role in protecting skeletal muscle and other body tissues from oxidative damage.
Glutathione helps maintain compounds such as iron in its proper oxidation state in hemoglobin. Protein sources containing high levels of cysteine (whey contains 2-2.5 percent cysteine) may be effective in maintaining or replenishing whole blood glutathione.
Whey Protein Supplements
Whey protein isolate is the most pure and concentrated form of whey protein available. It contains 90 percent or more protein and very little (if any) fat and lactose. Whey protein concentrate has anywhere between 29-89 percent protein depending upon the product.
As the protein level in whey protein concentrate decreases, the amounts of fat and/or lactose usually increases. Another type of whey protein supplement is whey protein hydrolysates, meaning that the whey is predigested into peptides (small chains of amino acids). These supposedly help the protein be absorbed better.
Increased protein synthesis, enhanced immune function and antioxidant activity, and fast absorption.
It has not been shown to be effective at decreasing protein degradation (in most cases).
This is excellent to consume around workout time due to its fast absorption rate. Consume it pre-, during, or immediately post-workout.
Casein Versus Whey
There seems to be a great deal of controversy over which one is better. I get the question all the time. From the information above, you can see that each offers distinct advantages and disadvantages. Below is information that directly compares casein and whey.
A study conducted by Yves Boirie looked at healthy subjects with a normal protein intake. They fasted for ten hours then were either given 30 grams of whey protein or 30 grams of casein (milk) protein.
The study showed blood leucine levels peaked in one hour after ingestion of whey or casein. However, the whey group peaked at higher levels and returned to baseline after four hours. The casein group peaked at a lower level but didn't return to baseline until seven hours later.
Whey protein enhanced protein synthesis (postprandial protein synthesis was stimulated by 68 percent with the whey protein), but did not effect protein degradation. Casein decreased protein degradation, (protein breakdown was inhibited by 34 percent after casein ingestion) but did not effect protein synthesis.
Postprandial whole body leucine oxidation over seven hours was lower with casein. Leucine intake was identical in both meals. Therefore, the net leucine balance over the seven hours after the meal was more positive with casein than with whey.
The study conducted by Boirie points out the benefits of both proteins as we mentioned earlier. Keep in mind that a mixed protein meal would have a different absorption rate that might change the effects on protein synthesis and breakdown. With the information from the study above, we must question the old saying, "We need to eat every three hours or we will lose muscle" (probably started by a supplement company).
A study by Tipton concluded that the acute ingestion of both whey and casein after exercise resulted in similar increases (no significant differences) in muscle protein net balance, resulting in net muscle protein synthesis despite different patterns of blood amino acid responses.
On a final note, one study indicated that whey protein might be more beneficial than casein in elderly subjects to limit body protein loss. However, more long-term studies are needed to confirm this age-related effect.