The importance of protein in nutrition is momentous to ones health. Dietary proteins are essentially nutritional because of their constituent amino acids, which the body uses to synthesize its own proteins, as well as nitrogen-containing molecules that are essential for life. The Recommended Dietary Allowance (RDA) for daily protein intake in healthy adults is 0.8 g/kgBW/day. Younger individuals who participate in recreational or competitive activities, however, often attempt to go beyond the RDA by using protein supplements to help increase performance. For example, it was demonstrated that protein supplementation in conjunction with an eight-week resistance-training program elicited greater improvements in muscle hypertrophy and strength when compared to carbohydrate supplementation in untrained men. There were 3.2 to 17.5% increases in muscle cross-sectional area of the quadriceps femoris musculature and 14.5 to 30.3% strength gains in the leg extensors. Furthermore, several expert groups have recently advocated that certain individuals, such as older persons, should increase their daily intake to 1.0 to 1.5 g/kgBW/day to support the preservation of muscle and function. Other conditions also place greater than normal demands on amino acids, such as hypercatabolic stressed states, like that experienced by burn patients who's muscle protein breakdown rate increases by impairment to inward transmembrane transport of circulating blood amino acids. It was also found that an experimental enriched protein "medical food" comprised of 27% of calories as total protein resulted in postprandial increases in MPS rates for 5 hours by ∼33% (0.073 ± 0.023%∙h-1 to 0.097 ± 0.033%∙h-1) in advanced cancer patients. Thus, continually reassessing new and innovative nutrient therapies is necessary for extending the findings of existing studies after technological advances, and for providing nutritional support-to-support health.

It is well known that dietary protein is a powerful transient stimulator of the muscle protein synthetic rate (MPS) whereby changes in MPS in response to feeding may be regulated by specific downstream target proteins of mammalian target of rapamycin signaling, such as S6K1, rpS6, and eIF2B. A meal deficient in protein, however, does not increase the rate of MPS because a rise in the bioavailability of amino acids does not occur. In addition, the source of dietary proteins has been shown to impact postprandial blood levels of amino acids. The concept that certain types of proteins are "fast acting" or "slow acting" has been shown to affect the postprandial profile of amino acids appearing in the systemic circulation. Native whey and micellar casein are both dairy proteins that contain a similar amount of essential (EAA), but blood EAA levels increase faster and to a higher level after the consumption of whey protein. Differences in gastric emptying, digestion and absorption kinetics between micellar casein and native whey are suggested to be the underlying factors. Nonetheless, micellar casein protein has been shown to protract MPS in humans. Despite the significant amount of information gained with respect to both of these protein sources, the effects of combinatorial formulations on the postprandial profile of amino acids appearing in the blood is less well known. The purpose of the present study is to test a novel blend of micellar casein combined with native whey to determine post-ingestion aminoacidemia, glycemia, and insulinemia in young adult men.