Ingesting ascorbic acid, or vitamin C, before a single bout of exercise “increases antioxidant power in [blood] and appears to mitigate the exercise-induced increase in superoxide dismutase activity,” wrote researchers from Chiang Mai University in Thailand.
Superoxide dismutase activity, they explained, is a marker of stress in the body. They found that this activity was significantly elevated after exercise paired with ingesting a placebo pill, but suppressed when the participants ingested the ascorbic acid pill.
Vitamin C is an antioxidant. The researchers argued that efficacy of vitamin C supplementation on exercise-induced oxidative stress remains unclear, with “some studies demonstrating no effect, and others reporting a reduction in oxidative stress markers following exercise.”
Their goal for this study was to evaluate whether ascorbic acid supplementation before exercise may acutely support antioxidant defenses and glucose metabolism. They also sought to explore if ingesting ascorbic acid before a single bout of exercise in untrained healthy adults may prevent muscle damage.
For the latter objective, the researchers found no link in their present study. “Supplementation with ascorbic acid prior exercise improves antioxidant power but does not prevent muscle damage,” they wrote.
The results were published last week in the Journal of the International Society of Sports Nutrition.
Nineteen healthy women aged between 22 and 25 years participated in the study.
“It has been suggested that antioxidant supplementation may only improve performance when endogenous levels are already depleted, and after reaching normal concentrations, no further benefit is seen,” the researchers wrote, citing a 2007 study published in The Journal of Nutritional Biochemistry.
Hence, the participants they recruited were women who were sedentary and had not participated in any regular exercise training program for at least one year.
The study had a crossover design, which meant that the participants ingested one capsule for one exercise day, either a placebo or 1000mg of ascorbic acid supplied by The Government Pharmaceutical Organization of Thailand. Then, they wen through a week-long ‘wash-out’ period before visiting the lab again, ingesting a different capsule, and going through the same exercise and blood analysis protocol.
Blood samples were taken immediately before, immediately after and 30 minutes post-exercise to determine plasma albumin, total protein, glucose, oxidative stress and muscle damage markers.
There were several limitations in the study design, the researchers admitted. For example, the participants exercised in a fasted state, which means it is difficult to extrapolate these results to normal sporting conditions when athletes usually do not fast.
“Further investigation on ascorbic acid supplement during exercise is required to fully understand its interaction with other molecules,” they added.
Source: Journal of the International Society of Sports Nutrition
Published online, https://jissn.biomedcentral.com/articles/10.1186/s12970-019-0269-8
“Effects of ascorbic acid supplementation on oxidative stress markers in healthy women following a single bout of exercise”
Authors: Manita Yimcharoen, et al.