Examine publishes rigorous, unbiased analysis of the latest and most important nutrition and supplementation studies each month, available to all Examine Members. Click here to learn more or log in.

In this article

Antioxidants, anti-adaptations?

We’ve covered antioxidants and strength training before. This study is a bit different — it investigates whether vitamin C and vitamin E might impact adaptations to endurance exercise.

Study under review: Vitamin C and E supplementation prevents some of the cellular adaptations to endurance-training in humans

Introduction

Antioxidants are substances that protect cells from oxidizing chemicals, such as free radicals. High levels of free radicals, particularly from dietary sources and pollution, cause cellular damage and may contribute to cancer[1], heart disease[2], and other disorders. However, low to moderate levels of free radicals are produced[3] by moderate to intense physical exercise and can help cells to adapt to increased physical stress, as shown in Figure 1. On the other end of the scale, overtraining without the appropriate physical adaptations can overwhelm[4] the body’s ability to respond to the high levels of free radicals produced, and can damage the body in similar ways to other sources of free radicals. Vitamins A, C, and E are the primary dietary antioxidants.

Figure 1: How ROS may help muscle endurance and antioxidants may hinder it

Over 40% of the general population[5] and over 50% of elite athletes[6] in endurance sports take multivitamins and other dietary supplements. Due to the prevalence of supplements, particularly vitamins C and E, the question has been raised as to whether these supplements have a negative effect on endurance training and the mechanisms through which the body adapts to the cellular stress of endurance training. As previously mentioned, the body responds to the moderate levels of free radical production produced by endurance training by adapting at the cellular level. Over time[7], the body can sustain higher and higher levels of free radical production because it improves muscular function and increases its natural antioxidant responses. Thus, it’s possible that taking antioxidant supplements could neutralize the free radicals produced by the body in response to exercise, thus hindering the body’s ability to adapt to progressively higher levels of free radicals.

Most previous research attempting to investigate the role of vitamin C and E supplementation has focused on endurance training alone by testing participants before and after the endurance training period. The study under review was designed to examine not only endurance training, but also the effects on an acute exercise session before and after the endurance training protocol. The hypothesis is that some long-term cellular adaptations to training are partly due to the effects of transient responses immediately following an exercise session. Several previous studies also assessed a lower dose of 500 milligrams a day of vitamin C, whereas this study looked at a higher dose of 1000 milligrams a day.

Common dietary antioxidants include vitamins C and E, which help neutralize free radical molecules in the body. They are supplemented by a large portion of the population, including more than half of endurance athletes. Because it is believed that free radicals contribute to the training adaptation resulting from endurance training, researchers hypothesized that antioxidant supplementation might reduce this adaptive response.

Who and what was studied?

Become an Examine Member to read the full article.

Becoming an Examine Member will keep you on the cutting edge of health research with access to in-depth analyses such as this article.

You also unlock a big picture view of 400+ supplements and 600+ health topics, as well as actionable study summaries delivered to you every month across 25 health categories.

Stop wasting time and energy — we make it easy for you to stay on top of nutrition research.

Try free for two weeks

Already a member? Please login to read this article.

What were the findings?

Become an Examine Member to unlock this article.

Already a member? Please login to read this article.

What does the study really tell us?

Become an Examine Member to unlock this article.

Already a member? Please login to read this article.

The big picture

Become an Examine Member to unlock this article.

Already a member? Please login to read this article.

Frequently Asked Questions

Become an Examine Member to unlock this article.

Already a member? Please login to read this article.

What should I know?

Become an Examine Member to unlock this article.

Free 2-week trial »

Already a member? Please login to read this article.

Other Articles in Issue #14 (December 2015)

  • Investigating vitamin D as a performance enhancer
    Having sufficient vitamin D levels has been associated with better muscle recovery. This trial not only looks at the question of causality, but also addresses some potential mechanisms of vitamin D’s benefit for exercise.
  • Trans fats: “natural” might not mean “healthy”
    In the nutrition community, a common message has been that artificial trans fats are bad, however natural trans fats are not only okay but beneficial. This trial on blood lipids puts that to the test.
  • High versus low fat diets for insulin sensitivity
    More body weight means more risk for metabolic syndrome. But the question of whether more fat (and especially saturated fat) impacts insulin sensitivity hasn’t been adequately addressed until now.
  • Exercise, with a (tart) cherry on top!
    Berries have burst onto the research scene in recent years. Tart cherries have shown some of the most promise in certain areas, leading to this study of powdered tart cherry on exercise recovery.
  • Interview: Dan Pardi MS PhD(c)
    Dan Pardi is an entrepreneur and researcher whose life’s work is centered on how to facilitate health behaviors in others.
  • Root rage: The impact of ashwagandha on muscle
    So called “adaptogens” like ashwagandha are typically studied for stress-easing potential. A randomized trial looked into this popular herb for a different purpose: bolstering adaptations to weight training.
  • Does the Food Guide make my butt get fat?
    By Francy Pillo-Blocka, RD
  • I <3 green tea
    When it comes to curbing cardiovascular disease, it’s not all about reducing cholesterol. Green tea may help prevent oxidation of LDL, as is explored in this trial looking at green tea catechins both in vivo and in vitro.
  • Investigating slow carbs for metabolic rate
    Glycemic index, glycemic load, insulin index: only one of these is widely known by the public. But when it comes to keeping weight off, does glycemic index and total carb content actually have any impact?