A group of researchers analysed 44 randomised controlled trials particularly looking at the important role vitamin E plays in attenuating muscle damage caused by antioxidative stress and inflammation.
They said: “Despite the beneficial effects from antioxidant supplementation, effects of antioxidants on exercise-induced muscle damage are still unclear.”
The aim of the meta-analysis was to look at the effects of vitamin E throughout a range of trials and the quality of those trials was assessed using a collaboration risk of bias tool.
The research team discovered that dietary vitamin E supplementation had a protective effect on muscle damage represented by creatine kinase (CK) and lactate dehydrogenase and that muscle damage was more reduced when CK was measured immediately after exercise and those tested were athletes.
“Vitamin E supplementation when it was lower than 500 IU had more beneficial effects on exercise-induced muscle damage measured by CK,” they added
The findings in the studies, say the researchers, demonstrate the protective role of vitamin E when exercise causes damage to muscles.
They wrote: “Interestingly, beneficial effects of vitamin E supplementation on muscle damage showed singularity of optimal dosage or had different patterns between athletes and non-athletes.”
Dietary vitamin E more evidently decreased exercise-induced muscle damage immediately after exercise, demonstrated by CK. Given that CK concentrations typically peak within 24 hours of exercise the results suggested that vitamin E protected muscle damage more effectively at an early stage. Interestingly, the protective effects of vitamin E supplementation on exercise-induced muscle damage was relatively clear with lower dosage and atheletes. When compared to non-athletes, athletes who exercise on a regular basis have stronger antioxidant defense systems and lower oxidative stress. implying that vitamin E might work better at a certain dosage or propel a well-constructed antioxidant defense system.
The researchers said: “The current meta-analysis found that vitamin E had a protective effect on exercise-induced muscle damage and oxidative stress. It is worth noting that a previous meta-analysis reported that total mortality increased with a higher dosage of vitamin E supplementation. As a result, people who consumed low doses of vitamin E and exercised were expected to have beneficial effects on exercise-induced muscle damage and oxidative stress.”
Optimal vitamin E
Although there have been several studies, this one provides distinct perspectives on optimal vitamin E supplementation. First it considered the dosage effect and divided it into high and low dosages based in median value (500 IU) and the effects were analysed on exercise-induced muscle damage (CK) and oxidative stress.
“The results in this study showed that lower dosages based on the median value had greater protective effects. Our results showed a complementary relationship among exercise-induced muscle damage, oxidative stress and inflammations by confirming the results at once.”
The team did acknowledge some limitations in the study saying that other markers could not be analysed because of an insufficient number of studies especially when using vitamin E alone as a supplement. They said that although particular markers were extensively analysed, additional studies should be performed to look at more biomarkers to achieve more solid results. They also noticed several differences among the studies used in the meta-analysis.
“Despite subgroup analysis of time-point, daily dose and type of subject, differences in exercise types and intensities and duration of supplementation could be attributed to high heterogeneity and discrepancy of results among the studies.”
Can Low-Dose of Dietary Vitamin E Supplementation Reduce Exercise-Induced Muscle Damage and Oxidative Stress? A Meta-Analysis of Randomized Controlled Trials
Authors: Myunghee Kim et al