Published in the Journal of Dietary Supplements, the study tested 12 mg of astaxanthin (AX) per day in 20 women and found a lower respiratory exchange ratio (RER) during a 30-minute cycling test compared to placebo.
A lower RER suggests the body is relying more on fat and less on carbohydrates for energy.
“Two weeks of AX supplementation lowered RER values in an active female cohort, indicating a shift toward a greater reliance on lipid-dominant substrate preference at specific submaximal intensities,” the researchers wrote.
No differences were recorded for heart rate, blood lactate or perceived exertion.
Why women?
Previous studies investigating astaxanthin and fat use during exercise have reported mixed results, but most have focused on men.
The researchers turned their attention to women because they typically rely more heavily on fat during exercise, raising the possibility that they may respond differently to astaxanthin.
“Women represent a major consumer segment for nutritional supplements such as astaxanthin, yet the evidence base has been largely derived from male populations,” Dr. Karen Hecht, vice president of AstaReal, told NutraIngredients.
The participants had an average age of 22 and were recreationally active. Each took astaxanthin for two weeks and placebo for two weeks, with a two-week washout period in between.
Because all 20 women received both treatments, each participant acted as her own comparison.
“Unlike many previous parallel-group studies, this crossover design allowed each participant to serve as her own control, reducing inter-individual variability,” Hecht said.
“This increases the ability to detect subtle changes in metabolism and may help explain why we observed a significant effect on fat oxidation in this female cohort,” she added.
Astaxanthin and fuel use
For the exercise test, the women cycled continuously for 30 minutes as the intensity increased from 40% to 65% of their maximum power.
Researchers measured RER during the test alongside heart rate, blood lactate and perceived exertion.
Overall RER was lower following astaxanthin supplementation than placebo. The difference was significant across the cycling session, although the effect did not significantly differ by exercise intensity.
Susan Hamrahi, scientific communications specialist at AstaReal, said the lack of changes in the other measures was also of interest.
“The study results suggest that astaxanthin didn’t change how hard participants were working or how hard the exercise felt,” she told NI.
“Heart rate, blood lactate, and perceived exertion all remained unchanged. What did change was how the muscles fueled the work,” she continued.
The study did not measure whether that difference in fuel use translated to improved cycling performance or endurance.
The researchers also stopped short of explaining why astaxanthin produced the change, noting that the underlying cellular mechanisms still need to be established.
Two weeks of supplementation
The supplementation period was shorter than the four weeks or more used in some previous astaxanthin studies.
Hecht pointed to other recent research reporting effects following shorter periods of use.
“Several recent studies have reported effects of astaxanthin as soon as 4–14 days of supplementation,” she said.
“This suggests that astaxanthin benefits may be leveraged for situational or event-specific use rather than limited to sustained daily supplementation,” she added.
Whether a longer supplementation period would produce different results was not tested in the current study.
The researchers also noted the small sample size and limited population. The participants were young, recreationally active women, and the exercise protocol only tested submaximal cycling.
AstaReal supplied the astaxanthin and placebo capsules but did not fund the study, according to the authors.
Hunter Waldman, an associate professor of kinesiology at the University of North Alabama and one of the study authors, disclosed that he serves as an adviser to AstaReal and has previously received funding for astaxanthin research.
Source: Journal of Dietary Supplements. doi: 10.1080/19390211.2026.2705844. “Astaxanthin Supplementation Lowers Respiratory Exchange Ratio During Submaximal Cycling in Females: A Randomized, Double-Blind, Placebo-Controlled Crossover Trial”. Authors: G.A. Barker et al.
