Credit: Pixabay/CC0 Public Domain
It is often said that exercise is the best medicine, but for many older adults, it can be a prescription that is increasingly difficult to take. Age-related physical and mental health challenges frequently make regular activity hard to sustain.
A study published in Dietetics by scientists at UT Health San Antonio, the clinical enterprise of The University of Texas at San Antonio, has explored whether adding branched-chain amino acids (BCAAs) to an exercise program could improve outcomes for older adults. In a small, randomized, double-blind, placebo-controlled trial, the team found that BCAA supplementation improved performance, reduced fatigue, and alleviated depression symptoms for many participants.
Inflammation and amino acids
“We’ve been studying for years how inflammation contributes to functional decline with normal aging or during disease, and among the many factors implicated in this process, the metabolism of amino acids appears to play an important role,” said study co-author Jason O’Connor, Ph.D., an associate professor in the Department of Pharmacology who also has a joint appointment at the Veterans Administration through the Geriatric Research Education and Clinical Center.
His research focuses on how inflammation impairs central nervous system function. BCAAs—leucine, isoleucine, and valine—are essential amino acids that not only serve as the building blocks of protein and muscle but also appear to play specific roles in inflammation and brain health.
“During inflammation, the metabolism of amino acids changes in a way that directly and indirectly impacts other processes. We are interested in getting some additional clarity about the brain-based component of fatigue versus the physical factors,” O’Connor said.
The complexity of fatigue
Rather than merely introducing a sense of tiredness, fatigue is a complex and debilitating condition. It can stem from muscle weakness, called motor fatigue, but can also involve the brain, called central fatigue, where the perception of fatigue resides. This brain-based contribution to fatigue is not particularly well understood, but many factors can contribute to it, including disturbed sleep, cardiovascular disease, or chronic inflammation.
While exercise is one of the most effective ways to counteract fatigue, many older adults find it hard to maintain consistent activity, particularly if one or more of these other factors are present.
“Fatigue has the capacity to spiral. An individual may be physically capable of cleaning out the garage, for instance, but they don’t feel like they have the energy to do it. They feel fatigued, or their motivational state is suppressed. Then they feel guilty about not doing it. They ask others for help with the task, then feel guilty about that,” O’Connor said.
“When we think about mental health, the spiral is real. Individuals can find it very difficult to get ‘unstuck.” What if we could put the brakes on that spiral and provide an off-ramp to help individuals improve their quality of life?”
Short- and long-term benefits
BCAAs may have both short- and long-term benefits. In the short term, they may influence brain pathways that reduce mental fatigue and promote well-being. They may also aid recovery by reducing muscle breakdown and damage. In the long term, BCAAs can activate cellular pathways within the muscle tissue, such as the mammalian target of rapamycin (mTOR) signaling pathway, which supports protein building and prevents muscle breakdown.
Why older adults?
Previous research on the anabolic effects of BCAAs in younger populations has produced mixed results. Some studies show benefits, while others do not. O’Connor said that it was important to investigate supplementation in older adults, who are more vulnerable to both physical and mental fatigue.
“Our prior work suggests that inflammation—and more recently, aging—disrupts the amino acid balance in a way that can alter how these essential molecules enter the brain. In some studies, lower levels of these amino acids are associated with fatigue, particularly central fatigue,” O’Connor said.
“Through supplementation, we thought perhaps we could restore balance and reduce the burden of central fatigue, while also providing a boost to the physical benefits of exercise that results in a greater synergistic effect.”
The pilot study enrolled 20 men and women with obesity and an average age of 70. Participants were randomized into two groups and asked to complete eight weeks of moderate aerobic exercise and strength training. One group received a placebo beverage, while the other consumed a BCAA beverage in a 2:1:1 ratio, emphasizing leucine.
“In our evidence and from literature, these amino acids do more than just serve as building blocks for protein. They have direct effects. Leucine has an effect on skeletal muscle and interplays with other amino acids transported into the brain that potentially have an effect on mental fatigue,” O’Connor said.
After eight weeks, the results surprised the team.
“We had predicted that exercise alone was going to have a positive effect that supplementation would further enhance, but the effects of exercise alone were very modest. If this is representative of what happens in real life, it may help explain why many individuals have a hard time complying with exercise if they are not feeling a benefit,” O’Connor said.
After eight weeks, the exercise-only placebo group showed very modest or insignificant changes in strength and endurance, a 5% increase in fatigue, and scores on the depression scale increased. By contrast, the BCAA group showed a modest increase in strength and endurance, a 45% decrease in fatigue and a 29% reduction in depressive symptom scores.
O’Connor hopes to expand the research to larger clinical trials, particularly with military veterans.
“There is an unmet need to address fatigue and frailty in our veteran population. This population is aging, and they often have more secondary health complications than the general population,” he said.
In addition, his team is finishing work on a study testing the effects of supplemental leucine on physical and cognitive performance in aged mouse models. O’Connor said the preliminary results look promising in terms of supplemental leucine enhancing the effects of exercise alone.
“There is a general notion that getting older also entails having more inflammation. In follow-up studies, we plan to analyze biological parameters to see if there is a relationship between the functional changes that we saw with physical performance and mental health measures and changes in the immune system,” O’Connor said.
More information:
Ronna Robbins et al, Branched-Chain Amino Acids Combined with Exercise Improves Physical Function and Quality of Life in Older Adults: Results from a Pilot Randomized Controlled Trial, Dietetics (2025). DOI: 10.3390/dietetics4030032
Provided by
University of Texas at San Antonio
Citation:
Amino acid supplement may boost exercise benefits for older adults (2025, October 30)
retrieved 2 November 2025
from https://medicalxpress.com/news/2025-10-amino-acid-supplement-boost-benefits.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.