In an effort to provide glutamine to TPN patients in a form that can remain stable in liquid, the amino acid has been bonded with other amino acids, such as the dipeptide alanyl-glutamine.
Recent evidence regarding the cardioprotective benefits of soy isoflavones has stimulated an increase in consumption of soy protein powders. Although consumers are most likely ingesting soy powders for the isoflavones present, they will also benefit from the protein itself. Studies on nitrogen balance in man indicate that isolated soy is comparable to that of animal proteins The effects of a soy-based diet versus an animal protein-based diet on whole-body protein turnover was evaluated using two groups of six males. The rates of protein synthesis and protein breakdown were similar in both groups. However, more recent research compared soy with casein on net protein retention in pigs. Constant infusions of either casein or soy were performed with measurements taken postabsorptively and 2-6 hours after the enteral feeding. Amino acid and urea kinetics were assessed using a primed-constant infusion protocol with L- [ring-2,63H]phenylalanine, L-[3,4-3H]valine and [15N-15N]urea. During the meal, the appearance of amino acids into the portal vein and their uptake by the liver was lower with the casein infusion. Muscle uptake did not differ between the casein or soy infusions. The soy infusion stimulated a lower rate of gut protein synthesis and higher rate of muscle protein turnover. The casein infusion stimulated a higher rate of liver protein synthesis and degradation. In the postabsorptive condition, casein infusion did not alter liver urea production, whereas soy infusion significantly increased it. The researchers concluded that the soy protein is an inferior quality in comparison to that of casein protein. Soy is well tolerated and there are no adverse effects associated with its use. Soy stimulates lower rates of liver protein synthesis and degradation, therefore, future research on the combinations of soy with other proteins may prove insightful in providing a protein that not only lowers the risk for cardiovascular disease, but also maintains higher levels of protein synthesis and lower levels of protein degradation.Glutamine- Promotes Muscle Glycogen Storage In this study, seven male subjects of average physical fitness took part in three different trials. First, subjects performed bicycle exercise designed to deplete their fast and slow-twitch fibers of muscle glycogen. Then they received either An 18.5% solution of glucose polymer, 8 g of glutamine, or An 18.5% solution of glucose polymer plus 8 g of glutamine. During the three trials, they also received a continuous infusion of glucose for 2 hours. Plasma glutamine concentration increased dramatically after the ingestion of glutamine alone or with the glucose polymer. Glutamine concentrations were approximately 70% higher than baseline 30-45 minutes after glutamine ingestion. Moreover, glutamine ingestion had no effect on insulin levels. As expected glucose polymer ingestion (with or without glutamine) produced a substantive rise in insulin that lasted 30-90 minutes. Glutamine was as effective as the glucose polymer solution in increasing muscle glycogen after the glycogen-depleting exercise bout . According to the investigators, "Oral glutamine alone promoted storage of muscle glycogen to an extent similar to oral glucose polymer. Ingestion of glutamine and glucose polymer together promoted the storage of carbohydrate outside of skeletal muscle, the most feasible site being the liver."