It was noted that those consuming the combined supplement had significantly lowered carbon dioxide output (VCO2), respiratory exchange ratio (RER), heart rate (HR), and blood lactate levels, when compared with the placebo and vitamin C or GSK taken alone.
Furthermore, O2pulse, total haemoglobin and myoglobin in skeletal muscle tissue (tHb), and biological antioxidant potential (BAP) were increased in those consuming the combined supplement.
“In conclusion, combined vitamin C and glutathione supplementation was more effective in improving metabolic function, skeletal oxygenation, cardiac function, and antioxidant function during prolonged submaximal exercise in middle-aged triathletes,” the Korean researchers emphasise.
They add: “These findings could be valuable in guiding supplementation and optimizing performance strategies for middle-aged triathletes and potentially other athletes with similar exercise demands and physiological profiles.”
Stress and athletic performance
It has been established that excessive reactive oxygen species (ROS), resulting in oxidative stress within the body, can occur following elevated high-intensity exercise. In addition, proinflammatory cytokines, causing inflammation and muscle damage, can contribute to a decreased exercise performance.
Previous research has shown that increased intakes of antioxidants, such as vitamins A and C, and glutathione, can prevent the accumulation of free radicals and thereby reduce oxidative stress. Thus, there is potential for antioxidant supplementation to enhance exercise capacity and recovery.
Studies investigating this effect using vitamin C and GSK have still remained inconclusive, which may result from significant inter-study heterogeneity.
Thus, the researchers conducted the randomised controlled trial to investigate GSK and vitamin C derived from yeast fermentation, and the effects on metabolic, cardiovascular, and antioxidant function during prolonged exercise.
The RCT utilised 12 middle-aged triathlon athletes, with an average age of 49. The participants completed a 90-minute submaximal cycling trial, corresponding to a 70% maximal oxygen intake. This followed intake of supplements containing either vitamin C and GSK, GSK, vitamin C, or a placebo.
The supplements contained 110 mg of vitamin C and 252 mg of food-grade GSK extracted from yeast (ActiveNrich).
It was reported that VCO2, RER, HR, and blood lactate after exercise were all significantly lower within the group supplemented with both vitamin C and GSK, suggesting improvements in skeletal and cardiac functionality.
In addition, it was noted that O2pulse, tHb, and BAP were significantly higher within this group, highlighting further potential benefits to antioxidant function.
The study suggests a substantial benefit to various parameters of health during and following the performance of sub-maximal exercise.
Regarding the observed effect on cardiac function, the researchers explain the significance of these findings: “A lower HR at the same intensity is thought to indicate an improvement in exercise economy. This can be attributed to the altered myocardial cellular metabolism, which may result in more efficient energy production or utilization, leading to improved energy efficiency.”
“Antioxidant supplementation can remove excess ROS, reduce inflammation, and stabilize the oxidative-reductive environment, thereby improving skeletal muscle blood flow and oxygen utilization capacity,” they add, explaining the hypothesised mechanism for improved antioxidative capacity.
Yet, they emphasise the need for further research to validate and established specific dosing recommendations to achieve optimal health outcomes, whilst assessing the long-term effects for athletes.
“Enhancing Supplemental Effects of Acute Natural Antioxidant Derived from Yeast Fermentation and Vitamin C on Sports Performance in Triathlon Athletes: A Randomized, Double-Blinded, Placebo-Controlled, Crossover Trial”
by Eunjoo Lee, Hun-Young Park, Sung-Woo Kim, Yerin Sun, Jae-Ho Choi, Jisoo Seo, Yanghoon Peter Jung, Ah-Jin Kim, Jisu Kim and Kiwon Lim