Update: More Studies Show Vitamin C & E May Reduce Endurance Capacity & Performance

Updated March 28, 2017

It has been 3 years since we first released the discussion on the effects of Vitamin C and E on endurance capacity and performance. At that time, this was a relatively “young” concept and went against the norm.

In situations involving a controversial discovery such as this, it is important to continue to pay attention to related research to make sure the concept continues to be supported. If not, it is time to adapt your practices! However, in this circumstance, the research has continued to support our position that antioxidant supplementation hinders adaptation to endurance exercise. You can see the original discussion below, but we thought it pertinent to provide a brief update on recent research on this topic.

In a 2015 article, Morrison et al. found that Vitamin C and E supplementation did not attenuate skeletal muscle oxidative stress or gene expression, however it did hinder other skeletal muscle adaptation in young healthy males (such as superoxide dismutase and mitochondrial transcription factor A). Santos et al. also confirmed that taking a vitamin E supplement 1 hour prior to exercise at elevation reduced inflammation markers. As covered in the discussion below, these inflammation markers are what lead to cellular adaptation. Bjornsen and colleagues looked at the effects of Vitamin C and E supplementation on lean muscle mass. Their findings follow suit with all research included in the original pos. They found that antioxidant supplementation slowed increases in lean body mass as a result of strength training.

It is important to point out that you should not avoid all foods that are sources of vitamins C and E. Paschalis et al. found that individuals who had low levels of vitamin C values showed decreased performance in aerobic exercise as well as increased oxidative stress. This does not support the need to supplement certain antioxidants. Rather, it supports the need for a well-balanced diet composed primarily of whole foods. I expect research to continue on this topic, and we will do our best to keep you all updated with any changes. However, at this point in time, our position that vitamin C and E supplementation hinders adaptation to endurance exercise continues to be supported.

Note: We removed vitamin C from EFS & Ultragen when this research was published in 2014.  EFS and EFS-PRO are one of the few during exercise drink mixes free from Vitamin C.

————Original Article———–

Antioxidant use has long been incorporated into the regular routines of numerous athletes. Historically, this has been especially true for endurance athletes. Antioxidants such as vitamins A, C, and E as well as Beta Carotene have long been suggested to protect active people from oxidative tissue damage. Although most evidence suggests non-athletes consuming a balanced diet do not benefit from additional antioxidant supplementation, numerous authors have encouraged endurance athletes to take supplemental antioxidants due to the increased oxidative damage which occurs as result of sustained physical activity. However, recent evidence suggests that antioxidant supplementation during endurance activity may actually hinder athletic performance.

labLet’s take a few steps back. Antioxidants are nutrients that act to prevent oxidative damage resulting from free radical formation. A free radical is a molecule that has an unpaired electron in its outer orbit making it highly reactive. They often react with a stable compound in order to pair its unpaired electron. Free radicals are believed to be produced in numerous ways. The most commonly cited mechanism of exercise related production is mitochondrial leak due to the increased oxygen flux to the mitochondria during exercise. Jenkins and Goldfarb (1993) estimated that 4-5% of the oxygen consumed in mitochondrial oxidation would eventually form oxygen species with unpaired electrons. More recent evidence suggests that other mechanisms may contribute more free radicals than mitochondrial leak including the inflammatory response, auto-oxidation of heme proteins, and ischemia-reperfusion. Regardless of how they are created, when free radicals are produced in excess, cellular damage can occur. Antioxidants can scavenge free radicals, bind metal ions to prevent them from reacting with reactive species, and even repair damage resulting from oxidation.

As previously suggested, antioxidant supplementation has become a commonplace with endurance athletes. Knez and Peake (2010) assessed the nutrition records of 37 ultraendurance triathletes for one week and found that all included subjects met or exceeded dietary reference intakes for all vitamins with the exception of Vitamin D. Over 60% of the athletes included in the study took vitamin supplements although only one athlete was recommended to do so based on formal medical advice. The most common supplements were Vitamin C (96%) and Vitamin E (80%), both antioxidants. The inherent dangers of this practice are relatively slim as most common antioxidant supplements are not toxic even at relatively high levels of supplementation. However, the overall benefits may not be all they have been purported to be and indeed may even hinder performance if taken at the wrong time.

The benefits of an antioxidant rich diet on enhancing the immune system have been well supported in literature. However, the benefits of antioxidant supplementation on performance are poorly understood. Numerous supplement companies suggest that antioxidant supplementation may possibly delay fatigue and improve endurance performance, however the scientific documentation supporting these claims have been lacking. In fact, recent evidence suggests it may be counterproductive to take antioxidants during endurance activities. Braakhuis and colleagues (2013) found that an antioxidant rich diet had no effect on performance in competitive rowers which was also the finding in Keith (2006). No evidence has been found supporting the use of vitamin E as an ergogenic aid either. According to Rokitzki et al. (1994) and Tidus et al. (1995), vitamin E supplementation had no performance effect in swimming, submaximal cycling, cycling to exhaustion, hockey, and marathon running.  Furthermore, in a separate 2013 study, the Braakhuis et al. found that consuming a beverage containing vitamin C during performance actually hinders performance in female distance runners. This supported the findings by Ristow et al. (2009) who suggested high levels of vitamins E and C led to a retard of training adaptations during exercise and was further supported by Gomez-Cabrera et al. (2008) who found high levels of vitamin C decreased endurance capacity.

Darcy AfricaThe fact that evidence now suggests the use of vitamin C during physical actually hindering performance may require a bit more explanation. There is a growing body of literature which supports the NEED for free radicals during exercise in order to enjoy the benefits of training adaptations. Reactive oxygen species have been shown to serve as a signal to promote the expression of skeletal muscle proteins, mitochondrial proteins, and heat shock proteins. Oral supplementation of Vitamin C has been shown to blunt the body’s natural ability to fight inflammation thus further limiting overall training adaptations. Furthermore, evidence suggests that endurance training promotes increased endogenous antioxidants in muscle fibers increasing the natural level of protection against exercise-mediated oxidative damage. Finally, it has been reported that vitamin C prevented expression of transcription factors which are involved in biogenesis which is consistent with the previous suggestions that vitamin C supplementation reduced training-induced adaptations. According to Braakhuis et al. (2013) training status appeared to have a greater impact on antioxidant mobilization after exercise than diet in elite athletes.

It is without a doubt that more research will be performed over this area in the future. Braakhuis et al. (2013) claimed to be the first to investigate the relationships between diet, exercise training, performance, and antioxidant status in elite athletes. Surely many more studies will follow. Based on the available evidence, it seems that a few conclusions can be made. First, most endurance athletes are already getting sufficient levels of most vitamins, including vitamins C and E. Endurance athletes with diets containing antioxidant levels which  exceed the dietary reference intakes will not likely improve performance. However, there may be an associated reduced risk for upper respiratory tract infections as well an increased ability to sustain iron status and heme proteins through the processes noted above. A final conclusion is that consuming antioxidants during endurance exercise may have a negative effect on performance. Athletes should focus first on gaining antioxidants through a balanced diet. However the addition of low level supplemental antioxidants may still provide health benefits.

Antioxidant References

Braakhius, A., Hopkins, W. G., & Lowe, T. E. (2013). Effects of dietary antioxidants and performance in female runners. European Journal of Sports Science,

Braakhius, A., Hopkins, W. G., & Lowe, T. E. (2013). Effect of dietary antioxidants, training, and performance correlates on antioxidant status in competitive rowers. International Journal of Sports Physiology and Performance, 8, 565-572.

Faff, J. (2001). Effects of the antioxidant supplementation in athletes on the exercise-induced oxidative stress. Biology of Sport, 18(1), 3-20.

Gomez-Cabrerra, M. C., Domenech, E., Romagnoli, M. Et al. (2008). Oral administration of vitamin C decreases mitochondrial biogenesis and hampers training-induced adaptations in endurance performance. American Journal of clinical nutrition, 87, 142-149.

Jenkins, R. R., & Goldfarb, A. (1993). Introduction: Oxidant stress, aging, and exercise. Medical Science Sports Exercise, 25(2), 210-212.

Keith, R. E. (2006). Sport nutrition: Vitamins and trace minerals. CRC Press: Boca Raton, FL.

Knez, W. L. & Peake, J. M. (2010). The prevalence of vitamin supplementation in ultraendurance triathletes. International Journal of Sport Nutrition and Exercise Metabolism, 20, 507-514.

Powers, S., Nelson, W. B., Larson-Meyer, E. (2011). Antioxidant and vitamin d supplements for athletes: Sense or nonsense?. Journal of Sports Sciences, 29(S1), S47-S55.

Ristow, M., Zarse, K., Oberback, A., Kloting, N., et al. (2009). Antioxidants prevent health-promoting effects of physical exercise in humans. Proceedings of the National Academy of Sciences of the United States of America, 106(21), 321-333.

Robson, P. J., Bouic, J. D., Myburgh, K. H. (2003). Antioxidant supplementation enhances neutrophil oxidative burst in trained runners following prolonged exercise. International Journal of Sport Nutrition and Exercise Metabolism, 13, 369-381.

Rokitzki, L., Logemann, E., Huber, G., et al. (1994). Alpha-tocopherol supplementation in racing cyclists during extreme endurance training. International Journal of Sports Nutrition, 4, 253-264.

Tidus, P. M., & Houston, M. E. (1995). Vitamin E status and response to exercise training. Sports Medicine, 18, 1079-1086.

—–New Studies Supporting Article Update—

Bjornsen, T., Salvesen, S., Berntsen, S….& Paulsen, G. (2016). Vitamin C and E supplementation blunts increases in total lean body mass in elderly men after strength training. Scandinavian Journal of Medicine and Science in Sports, 26(7), 755-764.

Morrison, D. Hughes, J, Della Gatta, P.A., Mason, S., Lamon, S., Russell, A.P., & Wadley, G.D. (2015). Vitamin C and E supplementation prevents some of the cellular adaptations to endurance-training in humans. Free Radical Biology Medicine 89, 852-862.

Paschalis, V. Theodorou, A, Kaparos, A…& Nicolaidis, M. (2016). Low vitamin C values are linked with decreased physical performance and increased oxidative stress: Reversal by vitamin C supplementation. European Journal of Nutrition, 55(1), 45-54.

Santos, S.A., Silva, E. T., Caris, A. V., Lira, F. S., Tufik, S., & Santos, R. V. (2016). Vitamin E supplementation inhibits muscle damage and inflammation after moderate exercise in hypoxia. Journal of Human Nutrition and Dietetics, 29(4), 516-523.


13 replies
  1. Greg
    Greg says:

    MultiV contains >600%DV each of Vitamin C and E, and the recommendation is to take it 1-2 hours before excercise/race. This seems to contradict the research above in both absolute levels of supplementation and supplement timing. Is the new “HP” version going to be more consistent with the above? And I’m going to put in one vote to please not increase the price for a new version….

  2. Robert Kunz
    Robert Kunz says:

    This is a great question. The MultiV formula contains 400mg Vitamin C and 200IU Vitamin E. Historically high levels of Vitamin C were used to combat oxidative damage and as well as upper respiratory tract infections following exhaustive exercise. We still believe this to be true, however is it at the expense of training adaptation?
    There is a good basis of new research trying to determine the exact mechanism and impact of using Vitamin C & E during exercise, however all questions have not yet been answered. A meta-analysis of the current research indicates that high levels (1g+ Vitamin C & 800IU Vitamin E) supplementation DURING exercise may hinder performance and training adaptations. Moderate to low levels of these nutrients do not seem to have the same effect. The 2013 Braakhius showed that consuming low levels vitamin C (15mg with other anthocyanidins actually improved performance in female runners whereas those consuming 1g vitamin C had a detrimental effect on performance. A study using 250mg VitC and 400IU vitamin E showed no significant difference as compared to a placebo.

    Due to this research we removed Vitamin C from EFS drink to assure our athletes were not consuming this antioxidant DURING exercise and to assure our athletes were no longer consuming over 1g.

    The take away message and our recommendation which is based on the body of evidence available today is that consuming low levels of Vitamin C & E during the day or post exercise still offers some benefit. We do not recommend athletes consume any drink or supplement containing Vitamin C & E DURING exercise, nor do we recommend consuming high levels of these nutrients.

    Our new MultiV-HP will be FREE of Vitamin C & E, however it will also contain a well research 1,3-1,6 Beta-Glucan that has impressive clinical research on its ability to ward off upper respiratory infections and improve immune response. The formula also has a strong blend of polyphenols and anthocyanidins from varied fruit extracts. This will allow athletes to gain the benefits of strong immune function without the possible detriment of high level Vitamin C & E supplementation. Our athletes will have a choice to use MultiV with low to moderate levels Vitamin C & E OR MultiV-HP which will be free of Vitamin C & E.

  3. Gi
    Gi says:

    Multi-V also contains a mixture that achieves 8,000 ORAC will this be present in the new blend? How about the effects of Coq10 and astaxanthin since both are considered antioxidants too. Are you planning to create a night time product that contains antioxidants and other items that should not be consumed pre or post workout? The article mentions how the antioxidants impact inflammation response. Omega3 and GLA (Omega 6) tend to impact inflammation too. Any correlation?

    • Robert Kunz
      Robert Kunz says:

      Currently the detriment is specific to high levels of Vitamin C & E. Again in the 2013 Braakhius study one group consumed 15mg Vitamin C along with blackcurrant and found this group improved peak running speed. So the research indicates that fruit extract anthocyanidins like those found in our ORAC blend don’t seem to elicit the same response as Vitamin C & E at high doses. Remember that the research is looking at Vitamin C & E consumption DURING exercise and has not shown any clear evidence that taking these supplement at other times of the day has any negative impact.

  4. John
    John says:


    What I’ve always liked about First Endurance is that your products actually work. Continually looking to better your products and doing the research necessary, really shows. There are lots of products out there to help endurance athletes but your products have always performed better than anyone else.

    Doing the research to validate what is discussed above and altering your products, if necessary, just shows that you’re committed to producing the best product.

    • Gil
      Gil says:

      I agree. First Endurance relies on actual clinical results and adjusts products as new results become available. There’s a lot of mis-information about supplements, but the claimed benefits and clinical results typically don’t match. First Endurance approach is a refreshing change.

      • Robert Kunz
        Robert Kunz says:

        To that point, several articles have already been written about vitamin c & e where the author concluded/recommended athletes not use these vitamins. Clearly the research did not show that vitamin c & e need to be completely removed. The research only indicated that at HIGH levels of these two vitamins taken DURING exercise may have detrimental effects. Often conclusions are taken too far and recommendations are made that are too broad.

  5. Robert Kunz MS
    Robert Kunz MS says:

    With several new studies further supporting the mechanism that vitamin c & e hinders endurance gains, First Endurance has upgraded their products to assure our athletes get them most out of their training. EFS, EFS liquid shot and EFS-PRO are all free of vitamin c & e, making these one of the few during exercise drinks on the market without these vitamins. In addition MultiVPRO is the only Multivitamin free of vitamins c & e. Ultragen is also free of vitamin c & e.

  6. Thomas Hoffman
    Thomas Hoffman says:

    Dr Gregor from NutritionFacts.org has covered this topic in the past. What he reported from the results is inline with this in that supplementation does in fact hinder adaptations. However, getting your vit C and E from food does NOT hinder adaptations. Bottom line, get your antioxidants from your food, not a pill.

    (it gets relevant after about minute 3)

    • Robert Kunz MS
      Robert Kunz MS says:

      Correct, though we have to be careful stating antioxidants versus vitamin c/e. Certainly we can assume that all antioxidants might work as such, but the reality is that we ONLY know that consuming vitamin c/e during exercise hinders adaptation.

  7. Gary
    Gary says:

    But using the drink for a long competitiion say 24 to 48 hour adventure race means you would want the antioxidents during competition just not training. You also might want to have the anitoxidnets during a taper leading up to a A race???


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  1. […] From this comparison you can clearly see that if EFS Drink is used at 1/2 strength, it yields more electrolytes, more amino acids, less total sugar and hence a lower osmolality all at a significantly lower cost.    EFS is also the only drink without vitamin C, because the latest research shows it may compromise endurance and performance. […]

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