Author(s)

Michael Dellogono¹, Lyra Clark¹, Mahdi Garelnabi^1,2, Thomas A. Wilson^1,2*

¹Biomedical Engineering and Biotechnology Program, University of Massachusetts Lowell, Lowell, MA, USA.
²Department of Biomedical and Nutritional Sciences, University of Massachusetts Lowell, Lowell, MA, USA.

Athletes often use branched-chain amino acid (BCAAs) supplements with a ratio of 2:1:1 (leucine:isoleucine:valine) for their impact on muscle building. Research suggests that by altering the ratio, an improvement in glucose metabolism might be possible. The purpose of this study was to examine how isoleucine would influence glucose tolerance. We recruited healthy male (n = 13) and female (n = 5) participants who were asked to fast for 12 hours before coming to the laboratory. A fasting blood sample was collected, followed by the subjects consuming a breakfast containing 113 g carbohydrates, 8 g protein, 1.5 g fat, and BCAA powder in the 2:1:1 ratio (Control) or BCAA powder enriched with Isoleucine (2:6:1), both added to orange juice. The opposite meal was consumed on a second visit one week apart. Blood was collected at 30, 60, 90, and 120 minutes post-meal. No differences were observed between the Control and Isoleucine for changes in serum glucose or insulin response when examining all subjects together. However, when comparing between genders, males tended to have a significantly lower serum glucose response compared to females when consuming the Isoleucine, with no difference between the genders when consuming the Control. Also, males had significantly lower serum glucose responses when consuming the Isoleucine compared to when they consumed the Control, while females had significantly higher serum glucose responses when consuming the Isoleucine compared to when they consumed the Control. In general, males tended to have a lower serum insulin response than females when consuming both the Control and the Isoleucine. Our study indicates a significant difference in the way genders respond to BCAA supplementation, where isoleucine may improve glucose tolerance and insulin response in males but not females.

Isoleucine, Branched-Chain Amino Acids, Glucose Tolerance, Insulin

Dellogono, M. , Clark, L. , Garelnabi, M. and Wilson, T. (2025) Isoleucine Enriched Branched-Chain Amino Acid Supplement Improves Glucose and Insulin Sensitivity in Healthy College-Age Males but Not in Females. Food and Nutrition Sciences, 16, 137-152. doi: 10.4236/fns.2025.161008.