Effects of branched-chain amino acid supplementation on plasma concentrations of free amino acids, insulin, and energy substrates in young men
Zhang Y, Kobayashi H, Mawatari K, Sato J, Bajotto G, Kitaura Y, & Shimomura Y
Journal Title (Medline/Pubmed accepted abbreviation): J. Nutr. Sci. Vitaminol.
Year: 2011
Volume: 57
Page numbers: 114-117
doi (if applicable):
Summary of Background and Research Design
Background: Branched-chain amino acids (BCAAs; leucine, valine, and isoleucine) are essential amino acids that stimulate muscle synthesis and contribute to the amino acid pool for building muscle proteins. Preliminary research showed that ingestion of BCAAs can decrease the blood concentration of other amino acids in women, but it is unknown if this effect holds true in men.
Hypothesis/purpose of study: How does the ingestion of BCAAs affect the blood concentration of all the amino acids, glucose, insulin, free fatty acids, and urea nitrogen?
Subjects: A total of 5 males, age 22-25 yrs.
Experimental design: Repeated measures design in which subjects participated in both treatments (there was no control treatment in this study)
Treatments and protocol: On the first day, the participants arrived at the laboratory after an overnight fast. A baseline blood samples was acquired and then the subjects consumed the beverage with 1 g of BCAAs. Seven additional blood samples were acquired during the subsequent 3 hrs. Five days later, the same participants repeated the procedure with a beverage containing 5 g BCAAs.
Summary of research findings
- Appropriately, a spike in BCAA concentration was noted in the blood after ingestion of the BCAAs, with the percent increase being proportional to the dose.
- Decreases in blood concentrations were noted in the amino acids methionine, phenylalanine, tryptophan, tyrosine, and arginine. These results were similar to what they observed in females.
- Plasma insulin levels transiently spiked after BCAA ingestion.
- There were significant changes in blood levels of glucose, insulin, free fatty acids, and urea nitrogen that occurred over time within each treatment.
Interpretation of findings/Key practice applications
When amino acid levels in the blood rise, it is expected for the body to take the amino acids into the tissues, break them down, and/or utilize them. The authors seemed to imply that the decrease in plasma concentration of some amino acids was negative, but it can not be ruled out that the decline in the plasma concentrations of these amino acids could have been due to a positive outcome, such as increased protein synthesis. From the data presented, it is not possible to determine an explanation for the declines in plasma amino acids that were observed.
Limitations
It is unclear why no true control treatment arm (e.g., water, isocaloric glucose, isocaloric/isonitrogenous amino acids) was included. In addition, the 1-way ANOVA analysis utilized only showed that there was a significant change in at least one of the amino acid concentrations within a particular treatment over the time periods at which samples were collected. Use of a repeated measures type of ANOVA that included factors such as time and treatment, along with appropriate posthoc tests, would have provided a great deal more information on how the 1- and 5-g treatments differed from each other and at what specific time points. Some changes in both the experimental design and statistical analysis might have rendered these findings more useful.
