The Korean crossover trial evaluated the supplement’s effects on aerobic exercise capacity and oxidative stress responses in male elite athletes and found that beneficial performance effects were evident after one week but not after a single intake.
“These findings support the potential benefits of one-week SLAB51 supplementation for exercise duration in elite athletes,” wrote researchers at Korea National Sport University in Nutrients.
However, given the study methods, they noted that these initial results warrant cautious interpretation and require further studies to clarify the mechanisms.
Probiotics and exercise performance
Aerobic energy production during exercise breaks down nutrients in the presence of oxygen to generate adenosine triphosphate (ATP), the body’s primary energy source. Increased oxygen consumption also leads to higher levels of reactive oxygen species (ROS) and oxidative stress, which can contribute to muscle fatigue and delay recovery.
However, ROS can also be beneficial, acting as signals that prompt the body to adapt to exercise, generate endogenous antioxidants, and increase endurance or strength.
Therefore, maintaining an appropriate balance between ROS production and antioxidant activity is fundamental to exercise performance and recovery.
Research suggests that by improving gut microbiota composition and intestinal integrity, probiotics can improve antioxidant defenses and can be considered antioxidant agents. The current study notes that previous evidence suggests that SLAB51 may influence physiological processes related to oxygenation and redox regulation, but there is a lack of studies determining its effects on exercise performance.
Study details
The study involved 36 male elite athletes who were randomly allocated into two groups to receive SLAB51, a multi-strain probiotic, or placebo for one week each. They crossed over into the other group after a two-week washout period.
Researchers performed assessments at the start of the study, after a single intake, and after one week of taking the supplement. They evaluated exercise performance using a treadmill-based Bruce protocol, measured markers of physiological and oxidative stress using blood samples, and analyzed the data using appropriate statistical methods.
The results revealed that both the supplement and placebo groups increased exercise duration from baseline, which the researchers noted could be due to repeated exposure to the treadmill test improving tolerance.
However, they observed a significant treatment condition × measurement time interaction for exercise duration “indicating that the pattern of change differed between the SLAB51 and placebo conditions,” they wrote.
Additionally, exercise duration continued to increase after week 1 of SLAB51 supplementation, whereas the placebo improvement was more limited.
The RER (Respiratory Exchange Ratio) indicated that participants taking the supplement may have been able to maintain exercise for a longer period after RER exceeded 1.0. RER 1.0 means that the body is relying on carbohydrates as a fuel source, having reached the anaerobic threshold.
However, the researchers noted that the performance results should account for the lack of significant differences in VO2max and for some measurements that the study didn’t assess.
The SOD activity suggested that “short-term SLAB51 supplementation may be associated with a favorable change in pre-exercise antioxidant-related physiological status,” the researchers wrote.
The researchers recommended further studies to confirm their findings and clarify the underlying mechanisms.
Source: Nutrients 2026, 18(19), 3299; https://doi.org/10.3390/nu18193299, “The Effects of Multi-Strain Probiotic SLAB51 Intake on Aerobic Performance and Oxidative Stress Responses in Elite Athletes: A Randomized Crossover Trial.” Authors: S-Y. Lee et al.
