A supplement you can buy over the counter may be the hack older adults need to get better results from exercise. A study of two groups of 70-year-olds found that branched-chain amino acids (BCAAs) combined with exercise improve physical function and quality of life. Exercise alone did not.
“I was a little surprised,” said study co-author Jason O’Connor, an associate professor in the Department of Pharmacology at UT Health San Antonio. “I expected exercise alone to be a primary driver of any benefit that we observed. The fact that we saw bigger effects and more positive, statistically significant improvement in the supplement plus exercise group suggests that it works.”
Amino acids are small molecules that are the building blocks for proteins and muscle. The supplement used in the study is a combination of specific amino acids called branched-chain amino acids (BCAAs), named for their molecular structure, that you can only get from your diet. But O’Connor, who also has a joint appointment at the Veterans Affairs system through the Geriatric Research Education and Clinical Center, wasn’t interested in them for their potential muscle-building properties, at least not exclusively. He was interested in them because of the pathway they use to get into the brain. It’s called the kynurenine pathway, which is also used by an amino acid with which many may be more familiar, called tryptophan.
“Tryptophan is the amino acid that most people would recognize as being the one that makes us sleepy after Thanksgiving dinner,” O’Connor said. As people age, the breakdown of tryptophan produces metabolites that are linked to fatigue and cognitive decline.
O’Connor wondered if the pathway used by tryptophan was blocked because BCAA were already using it; would that limit the production of damaging tryptophan metabolites that cause fatigue and that could interfere with regular exercise in older adults?
“We talk about this as restricting fuel to the fire,” O’Connor explained. “So if what we’re trying to effectively accomplish is to slow down that production of bad metabolites, one way that we’re trying to do that is by restricting the molecule.”
francescoridolfi.com/Getty Images/iStockphoto
/
iStockphoto
So that’s what O’Connor and his team did. They enrolled 20 men and women with obesity and an average age of 70 in a pilot study, randomly dividing them into two groups. Both groups were asked to complete eight weeks of moderate aerobic exercise and strength training. Both groups were asked to consume a beverage every day. One group received beverages with a BCAA supplement, and the other group received beverages with a placebo.
The results surprised everyone.
“We actually saw bigger and better effects than we were predicting,” O’Connor said. “Most notably, they improved in physical performance across the board. Every measure of physical performance was better.”
There were also dramatic improvements in cognitive assessments, but only for the group that consumed BCAAs along with exercise. The placebo group essentially saw no benefit. “So when we compared where they started to where they were eight weeks later after having finished the intervention, by and large supplementation in combination with exercise was superior to exercise alone,” O’Connor said.
Older adults often struggle to get the amount of exercise they need to make a difference in their overall physical and mental health. “The degree and level of exercise that’s required is probably more extreme than we are going to be able to attain in older individuals who have physical limitations on what they can do and how they can do it,” he said. But if a daily supplement could help them see results more quickly and with less effort, it could be a game-changer for this age group.
“If the amount of exercise that’s required to achieve benefit is lower, or if you feel the benefit of exercise sooner,” O’Connor said, “that is something that I think could move the needle.”
While this pilot study, which was published in Dietetics in August 2025, is exciting, it’s small. “We had 10 individuals in each group for our pilot study. That’s a very, very small sample size. We really want to see if this replicates in a bigger group,” O’Connor said.
Science & Medicine is a collaboration between TPR and The University of Texas Health Science Center at San Antonio that explores how scientific discovery in San Antonio advances the way medicine is practiced everywhere.