Antioxidant supplementation has been shown in several studies to hinder training improvements. For example, researchers compared an antioxidant supplement to a placebo among multisport athletes and soccer players. They found the placebo group experienced a 5.6% increase in VO2 max – a measure of aerobic fitness – compared to a 0% change in the antioxidant supplement group. This led authors to believe that the antioxidant supplement led to fewer training adaptations. (1)
A similar study was conducted among middle aged men doing high intensity exercise training using a specific antioxidant, resveratrol. Those taking the placebo experienced a 45% greater increase in VO2 max after an 8 week training program compared to the antioxidant group. (2) And a 3rd study found that another type of antioxidant supplement interfered with muscle repair and recovery after eccentric contractions (where the muscle lengthens while experiencing tension – think downhill running as an example). (3) Even a review from the an author from the US Olympic Committee questions the role of Vitamin C supplementation, noting controversial research and potential impaired sports performance. (4)
Our advice? Get your antioxidants through a diet rich in plant-based foods. I have not seen any research showing a negative effect of an overall balanced diet on athletic performance. Components of food may interact synergistically with one and other or may have a different effect in the body compared to supplements.
Protein Powders - Possibly Contaminated
My biggest concern with protein powders stems from the lack of regulation regarding purity – not the protein itself. For example, a 2010 Consumer Reports test found that several commercial protein powders and shakes were contaminated with higher-than-recommended levels of heavy metals, including arsenic and cadmium. (5) A 2013 Consumer Labs examination found certain brands had differing nutrition profiles than listed on the label (6). Last year, a line of Vega protein powders were recalled due to antibiotic contamination (7).
Most concerning for athletes is the possibility that these powders are contaminated with prohibited substances, or those that have a similar chemical structure to prohibited substances, which may trigger a positive test. For college and professional athletes, even unintentional consumption of these substances through supplements can lead to a temporary or permanent ban from competition.
Our advice? Try to meet your protein needs through real foods. These can come from animal-based sources, like chicken, beef, fish, and dairy products, or plant-based sources like tofu, edamame, nuts, seeds, beans, and lentils. While protein powders can be a logical dietary addition for athletes struggling to meet their needs, it’s important to research and select reputable brands.
Vitamin D2 Supplements - Questions About Muscle Damage
Vitamin D2 supplements caused increased muscle damage among NASCAR pit crew athletes. These athletes were given either a Vitamin D2 supplement or a placebo over a 6 week period, and those taking the D2 supplement experienced significantly increased muscle damage. (8) Note that this is the first study of it's kind using D2 and looking at muscle damage, so more research is needed before we can draw a definitive conclusion.
Our advice? Aim to get Vitamin D through dietary sources, short exposure to sunlight, or a Vitamin D3 supplement. Dietary sources of Vitamin D include egg yolks, fatty fish, and fortified dairy products. In the past, I have promoted Vitamin D2 as a good supplement for vegan athletes (Vitamin D3 is not vegan), especially those with darker skin who have decreased Vitamin D production from sunlight. Given this study, it will be important to continue to monitor the research to see if additional research supports the damaging effects to the muscle, and if there is a dosage threshold. The dose used in this study – 3800 IU – may be responsible for the damage, but perhaps lower doses are helpful.
Our advice is not a substitute for one-on-one advice from a medical doctor. If you have concerns about your supplement choices, please talk to your physician.
(1) Skaug A1, Sveen O, Raastad T. An antioxidant and multivitamin supplement reduced improvements in VO2max. J Sports Med Phys Fitness. 2014 Feb;54(1):63-9.
(2) Gliemann L1, Schmidt JF, Olesen J, Biensø RS, Peronard SL, Grandjean SU, Mortensen SP, Nyberg M, Bangsbo J, Pilegaard H, Hellsten Y. Resveratrol blunts the positive effects of exercise training on cardiovascular health in aged men. J Physiol. 2013 Oct 15;591(Pt 20):5047-59.
(3) Michailidis Y1, Karagounis LG, Terzis G, Jamurtas AZ, Spengos K, Tsoukas D, Chatzinikolaou A, Mandalidis D, Stefanetti RJ, Papassotiriou I, Athanasopoulos S, Hawley JA, Russell AP, Fatouros IG. Thiol-based antioxidant supplementation alters human skeletal muscle signaling and attenuates its inflammatory response and recovery after intense eccentric exercise. Am J Clin Nutr. 2013 Jul;98(1):233-45.
(4) Braakhuis AJ. Effect of vitamin C supplements on physical performance. Curr Sports Med Rep. 2012 Jul-Aug;11(4):180-4.
(5) Consumer Reports. What our tests found. 2010. http://www.consumerreports.org/cro/magazine-archive/2010/july/food/protein-drinks/what-our-tests-found/index.htm
(6) Consumer Labs. 31% of Protein Powders and Drinks Fail Tests by ConsumerLab.com. 2013. https://www.consumerlab.com/news/Protein_Powders_Reviewed/06_11_2013/
(7) FDA. Vega Issues Voluntary Withdrawal of Vega One Nutritional Shakes and Vega Sport Performance Protein Product Due to Traces of the Antibiotic Chloramphenicol. 2013. http://www.fda.gov/Safety/Recalls/ucm374392.htm
(8) Nieman DC1, Gillitt ND, Shanely RA, Dew D, Meaney MP, Luo B. Vitamin D2 supplementation amplifies eccentric exercise-induced muscle damage in NASCAR pit crew athletes. Nutrients. 2013 Dec 20;6(1):63-75.