Quantitative Analysis of Branched-chain Amino Acids in Five Nutritional Supplements Using a Leucine Dehydrogenase Assay (P23-004-19)

Abstract

ObjectivesThe objective of this experiment was to determine the branched-chain amino acid (BCAA) content in five different sport nutrition supplements compared to the amount claimed on the label. MethodsTo measure the BCAA content of five nutritional supplements, a leucine dehydrogenase enzyme assay was used. This enzyme catalyzes the reaction of turning the given BCAA (L-leucine, L-valine, and L-isoleucine), water, and NAD+ into their respective metabolite, NH3, NADH, and H+. Ultraviolet-visible light spectrophotometry (UV/Vis) was used at 340 nm to create a standard curve. This curve uses the Beer-Lambert Law to measure NADH concentration from absorbance. NADH is in a 1:1 ratio with each BCAA molecule thus relaying the content of the given sample. The assay is specific to the three BCAAs in their free form. Other amino acids, as well as BCAAs in oligopeptides, do not interfere with this experiment. Products including oligo- and polypeptides were not included for testing. The assay was performed for each product and ran against a known standard (≥98% L-leucine) for validation. Due to different supplements having different BCAA amounts per serving, % content of the claimed amount was measured. ResultsCompared to the amount provided by the labels of each supplement, BCAA content was on average only 61% of the manufacturer claims when compared to ≥98% L-leucine. This shows that these BCAA supplements do not meet label claims for BCAA content (P < 0.01). ConclusionsThe five tested nutritional supplements contain significantly less branched-chain amino acid content than claimed on the label. This experiment can be expanded on in the future to test content of other BCAA containing supplements to determine how common underdosing is in the industry as a whole. Funding SourcesThe author claims no funding sources.