We all know that exercising is good for us. Countless studies have shown that exercise helps with weight management, insulin sensitivity, mood, cholesterol control, and even the immune system.
But what you might not know is that you could be ingesting ingredients right now that are actually blocking the benefits of exercise.
And what is worse, you have probably been told these ingredients make you healthier.
The ingredients are vitamin C and vitamin E, both of which fall under the “antioxidant” category of nutrients.
You might be thinking I am crazy; how in the world could these two vitamins negate the positive effects of exercise?
I was surprised as well, so let me take you through a recent study1 that just might change the way we look at our supplements.
The Surprising Study About How Antioxidants Can Block The Benefits of Exercise
The study, published in The Proceedings of the National Academy of Sciences, took 40 people and divided them into two main groups.
One group was given 1000mg of vitamin C and 400IU of vitamin E daily, while the other group was given a placebo.
Both groups were then subjected to an aggressive 4-week training routine that included 20 minutes of biking or running, 45 minutes of circuit training, and a 20-minute warm-up and cool-down, five consecutive days per week.
Everything else remained identical, the only difference being the addition of the antioxidants in half of the participants.
Also important, before the 4-week training routine began, blood tests were drawn from all participants to establish baseline levels of glucose metabolism, insulin sensitivity, adiponectin and oxidative stress.
The Antioxidant Effect
After four weeks, final blood tests were taken to determine if there was an antioxidant effect.
In the group that received the placebo, the 4-week exercise program increased glucose metabolism, adiponectin levels and insulin sensitivity. It also increased the body’s production of its own antioxidants – glutathione and superoxide dismutase.
This is extremely positive information, reaffirming the benefits of exercising on a regular basis. It’s especially interesting that exercise increases adiponectin because high levels of this hormone are absolutely essential for fat burning.
So what happened to the group that consumed the antioxidants (vitamins C & E)? The short answer is, “Nothing”.
After the 4-week exercise program, the people in this group did not show any increase in glucose metabolism, adiponectin levels or insulin sensitivity. They also did not show an increase in the body’s production of its own antioxidants (glutathione and superoxide dismutase).
Well, I shouldn’t say absolutely nothing happened; the oxidative stress in the antioxidant group was in fact lower than the placebo group’s. One would think this would be a good thing, yet it appears to be precisely the reason why these antioxidants blocked the positive effects of exercise.
What is Behind the Antioxidant Effect?
Let’s explore oxidative stress, free radicals, antioxidants, and how they relate to exercise in a little more detail.
When you exercise, you increase your metabolism, creating oxidative stress in the form of reactive oxygen species (ROS), or free radicals, that attack our tissues at the cellular level. On the other hand, antioxidants have the opposite effect. They eliminate the kinds of free radicals that result from oxidative stress.
What the study demonstrates is that the formation of free radicals during and after exercise is a crucial mechanism that signals your body to increase glucose metabolism, adiponectin levels and insulin sensitivity, while also causing your body to produce more of its own antioxidants – glutathione and superoxide dismutase.
And by taking even relatively small amounts of antioxidants, like 1000mg of vitamin C and 400IU of vitamin E daily, you are eliminating the oxidative stress that is triggering this highly beneficial health cascade.
It appears more beneficial to allow your body to recover from the free radicals created by oxidative stress naturally than to interfere with this process by taking these particular antioxidants.
It’s similar in a way to testosterone replacement therapy. Once you replace your body’s natural testosterone with outside sources, you body stops producing its own. This is why responsible doctors are reticent to prescribe this therapy unless one’s testosterone levels are extremely low.
Should I Swear Off Antioxidants?
The obvious question is what to do with this information. As with any new research, it brings up more questions than answers.
We do not know whether this information extends to other antioxidants or just vitamin C and vitamin E. So let’s talk about just these two vitamins for now.
The recommended daily intake (RDI) for vitamin C is 75 mg. Studies show that a daily dose of 200mg fully saturates tissues, and higher dosages have shown few increased benefits.2 I don’t see a big reason to supplement for this vitamin because it is very easy to get 75mg to 200mg from natural food sources. For example, just one orange will provide you with around 100mg of vitamin C.
The RDI for vitamin E is 22.5 IU, and studies show that mega doses (averaging 400 IU) can actually lead to increased mortality3. Again, it’s easier and safer to get vitamin E from natural food sources like spinach, almonds, eggs, and olive oil.
A recurring theme in medicine is that “more is often less”. Just because an ingredient has a positive effect does not mean taking more will magnify the positive result. And just like with the exercise study, taking more vitamins can lead to worse (not better) results.
I will be diving much deeper into this topic because of the many unanswered questions. I would appreciate your questions and insights below.
I know it would be easy to jump to conclusions here, but I believe it is wiser to wait for more evidence. So for now, I would simply lower your dosage of vitamins C & E to the RDI if you plan on embarking on a vigorous exercise program.
Until next time,
Steve Sisskind, M.D.
Hi, I'm Dr. Steve Sisskind, Chief Medical Officer & Founder at RealDose Nutrition.
As a young physician, I struggled because my patients came to me with serious health issues, but I didn't have the right tools to help them. Medical school taught me how to put "band aids" on their symptoms with drugs and surgery, but not how to address the root causes of their problems.
Years later I discovered a better approach... based on the fundamental idea that the power of nutrition can transform your health and vitality. But there's a lot of confusion... What foods should I eat? Which supplements should I take? What does the science say?
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1. Michael Ristow, Kim Zarsea, Andreas Oberbachc, Nora Kloting, Marc Birringer, Michael Kiehntopf, Michael Stumvoll, C. Ronald Kahn, and Matthias Bluher. Antioxidants prevent health-promoting effects of physical exercise in humans. PNAS 2009 May;106(21):8665–8670.
2. Sebastian J. Padayatty, MRCP, PhD, Arie Katz, MD, Yaohui Wang, MD, Peter Eck, PhD, Oran Kwon, PhD, Je-Hyuk Lee, PhD, Shenglin Chen, PhD, Christopher Corpe, PhD, Anand Dutta, BS, Sudhir K Dutta, MD, FACN, and Mark Levine, MD, FACN. Vitamin C as an Antioxidant: Evaluation of Its Role in Disease Prevention. Journal of the American College of Nutrition, Vol. 22, No. 1, 18–35 (2003).
3. Miller Er, 3.; Pastor-Barriuso, R.; Dalal, D.; Riemersma, R. A.; Appel, L. J.; Guallar, E. (2005). “Meta-analysis: High-dosage vitamin E supplementation may increase all-cause mortality”. Annals of internal medicine 142 (1): 37–46.