Research Spotlight: Resistance training boosts your antioxidant system more than vitamin D supplementation

Research Spotlight articles share concise breakdowns of interesting studies. The study reviewed is "Elastic resistance training is more effective than vitamin D3 supplementation in reducing oxidative stress and strengthen antioxidant enzymes in healthy men" by Kalvandi et al. (2021)
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Vitamin D serves a plethora of functions in the human body, but one of its major functions is to regulate the endogenous antioxidant system. When most people think of antioxidants, they immediately think of vitamins that directly scavenge free radicals (vitamins C and E, in particular), or possibly phytochemicals with antioxidant properties. However, much of your body’s antioxidant capacity comes from its own endogenous antioxidant system – proteins and compounds your body produces, which scavenge free radicals.

Vitamin D is far from the only thing that influences your endogenous antioxidant system. Importantly, exercise plays an important role as well. As part of the adaptive response to exercise-induced inflammation, your body ramps up endogenous antioxidant production, so that subsequent exercise bouts will cause less oxidative stress.

With that in mind, a recent study set out to compare the effects of vitamin D3 supplementation and resistance training on oxidative stress and antioxidant capacity. Researchers recruited 40 young men with low vitamin D levels (their 25(OH)D levels averaged ~21ng/mL at the start of the study) to participate. Subjects were randomized into four groups. One group performed resistance training while supplementing with vitamin D3 (50,000IU, once per fortnight), one group performed resistance training while supplementing with a placebo, one group supplemented with vitamin D3 without performing resistance training, and the final group served as a control group (placebo supplement, and no resistance training). Resistance training consisted of band-resisted exercises for most major muscle groups, performed for 3-4 sets of 10-15 reps, three times per week for eight weeks.

Before and after the eight-week intervention, blood draws were performed to assess malondialdehyde (MDA; a marker of oxidative stress), superoxide dismutase (SOD; an endogenous antioxidant), total antioxidant capacity (TAC), glutathione peroxidase (GPX; another endogenous antioxidant), creatine kinase (CK; a marker of muscle damage), and serum vitamin D levels.

With the exception of creatine kinase (which didn’t change much in any group), and vitamin D levels (which obviously increased the most in the two groups supplementing with vitamin D3), beneficial changes were larger in the two exercise groups than the control group and the group just supplementing with vitamin D. Some of the changes in the group supplementing with vitamin D and performing resistance training may have been significantly larger than the changes in the group that just performed exercise, but the authors didn’t report results of statistical tests that would be necessary to make that determination (much like the partial range of motion study I reviewed this month, their post-hoc testing left a lot to be desired). However, the decreases in MDA, and increases in SOD, TAC, and GPX were all larger in the group that only performed resistance training, than the group that only supplemented with vitamin D3.

Overall, this study suggests that resistance training – even fairly easy resistance training – can improve the functioning of your endogenous antioxidant system to a greater extent than supplementing with vitamin D3, even if your vitamin D levels are quite low. To be clear, I’m not suggesting that there aren’t other good reasons to keep your vitamin D levels in the recommended range (above 32 ng/mL, or 80 nmol/L) – the benefits of vitamin D go well beyond its impact on your endogenous antioxidant system. Rather, I just wanted to use this opportunity to point out one of the benefits of resistance training that’s easy to overlook or forget about.

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