During periods of stress, hypermetabolism may result in the excessive catabolism of protein and lean body mass. An example of such a condition is severe thermal injury, whereby the protein requirements may be much greater than normal. Because whey proteins contain high concentrations of branched-chain amino acids (BCAAs), a comparison was made between different levels of dietary whey versus different levels of BCAAs on the recovery from severe burns in guinea pig Guinea pigs were divided into six groups.
Each group received either 10%, 20%, or 30% of their calories from whey or BCAAs. Although rates of protein synthesis were not measured in this study, the cumulative effects of nitrogen balance and mortality were significantly better in the whey protein groups than the BCAA groups. This provides evidence that WPC may prove superior to BCAAs in recovery from thermal stress because it provides other EAAs in addition to the BCAAs. The availability of other amino acids may allow whey to stimulate protein synthesis in which BCAAs may be limited due to rate-limiting amino acids.
Research on protein synthesis in humans incorporates the use of infused radiolabeled tracers under near-steady-state conditions by the additional infusion of nasogastric or nasojejunal feedings This practical application of this approach has been questioned because feeding is not constant in normal humans and the steady state may overshadow acute initial events. In addition, the plasma amino acid and hormone levels are different between single meal and constant feeding
Given this scenario, an appropriate study would be to investigate the effects of feeding an intrinsically labeled whey protein meal (no carbohydrates or fats present) on whole-body protein synthesis. Boirie et al. gave 30 g of a radio labeled whey protein to ten male subjects. The subjects had fasted overnight before receiving the tracer proteins. The results demonstrated an increase in wholebody protein synthesis, with little inhibition of protein breakdown. The investigators concluded that it appears dietary amino acids are geared toward protein synthesis and the formation of new amino acids, while old amino acids may be geared toward oxidation. In a later study by the same group, the digestion and absorption of whey were compared with casein.
Labeled casein and whey proteins were ingested as liquid meals without any carbohydrates or fats after a 10-hour fast. Whey protein ingestion resulted in a rapid, transient elevation of the plasma levels of amino acids. The sudden surge of amino acids results in an increased rate of protein synthesis and oxidation with little to no change in protein breakdown. These results were obtained after a 10-hour fast, which is not typical of normal human feeding patterns. The effects of a normal feeding pattern (i. e. , three meals plus snacks or several small meals) on protein metabolism would offer tremendous insight to the mechanisms behind protein accretion Nonetheless, it should be pointed out that there is no direct evidence in humans that shows that whey protein by itself can promote gains in lean body mass. And certainly, it would be difficult to perform a study in which whey protein could serve as the sole source of protein. However, the animal data are intriguing enough that further study on whey is warranted.
Safety and Toxicity
Research on the use of a whey protein concentrate in HIV/AIDS and cancer patients reports no side effects and an improved sense of well-being. Whey protein has also been used to treat cystic fibrosis in infants and cirrhosis in children, with positive results. However, the concern with ingestion of any type of protein concentrate or hydrolysate is the occurrence of an allergic reaction. In addition, whey protein ingested as an AAM could result in osmotic diarrhea if the oral dose is too high. This is a temporary event and can be dealt with by decreasing the dose.
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