Oxidative stress might be involved in the mechanism of exercise-induced fatigue and mental stress in otherwise healthy individuals, as well as the pathophysiology of prolonged fatigue, or chronic fatigue syndrome.
Based on this, researchers in Japan conducted a study to assess the effect of two food-derived antioxidants, astaxanthin and sesamin (AS), on fatigue.
They recruited 24 healthy volunteers and supplemented them with either AS or a placebo for four weeks, after which they were given an ergometer task to induce physical and a visual display terminal (VDT) task to induce mental fatigue.
Testing the mind and body
The researchers then measured their subjective fatigue with a visual analogue scale during and after both tasks, and used a questionnaire to evaluate their daily subjective fatigue.
Secondary outcomes included work efficiency, autonomic nerve activity, levels of an oxidative stress marker (plasma phosphatidylcholine hydroperoxide or PCOOH), safety, and other subjective feelings.
They reported that the participants who had been supplemented with AS saw "significantly improved recovery" from mental fatigue when compared with those who had been given a placebo, and did not experience any adverse effects.
In addition, heightened PCOOH levels observed during both the physical and mental tasks were diminished by AS supplementation.
However, when it came to the secondary outcomes, the researchers did not detect any differences between the participants who had received AS supplementation and those who had taken a placebo.
They reported the study's limitations, which included its small sample size.
There was also a carry-over effect observed in AS supplementation due to the mental and physical tasks being performed on two consecutive days, which prevented the researchers from determining the impact of AS on physical fatigue.
At the same time, because they did not measure the concentration of sesamin in plasma, the link between sesamin and subjective fatigue was unknown.
Furthermore, they only evaluated the continuous ingestion of AS, so they could not determine whether their findings were the result of continuous or single ingestion.
In conclusion, the researchers wrote: "As a result of this four-week randomised, double-blind, placebo-controlled, two-way crossover study, AS supplementation exhibited the effect of promoting recovery from VDT-induced mental fatigue.
"The increase in PCOOH during mental and physical tasks was attenuated by AS supplementation. Thus, anti-oxidative activity exhibited by AS could be a possible mechanism for its anti-fatigue effect.
"Our results suggest the novel possibility that supplementation with AS may reduce subjective fatigue in healthy subjects. The safety of a four-week AS supplementation period was also confirmed."
"Effects of Dietary Supplementation of Astaxanthin and Sesamin on Daily Fatigue: A Randomized, Double-Blind, Placebo-Controlled, Two-Way Crossover Study"
Authors: Ayano Imai, et al.