Are Antioxidants 'Bad' For You?

by Dr. Jason Barker February 20, 2014

Are Antioxidants 'Bad' For You?

Hmmm. So another study damning the use of antioxidants in exercise is afloat.

Like those previous to it, this study has been promoted with eye-catching headlines like “vitamins may be bad for your workout” and “antioxidants are harmful for exercise.”

This study (and it's predecessors) have looked at the use of antioxidants (most typically vitamins C and E) during exercise training to see what effect they have on training benefits, such as performance and recovery.

Without even mentioning that media-sourced headlines are almost always written to ‘shock’ you, I wouldn’t say that antioxidants are ‘bad’ or ‘dangerous’ after reading this latest study, as the headlines would have you believe.

Here’s what the study looked at:

54 men and women took either 1000 mg vitamin C plus 235 mg vitamin E OR a placebo during the course of an 11-week training cycle consisting of 3-4x weekly sessions of mixed high intensity and endurance-pace running.

They then measured the fitness indices of maximal oxygen uptake (VO2 max) and running performance.

Here’s what they found:

Max VO2 and running performance increased equally in both the antioxidant and placebo group. But, they found lower levels of specific biochemical markers that signify growth in numbers of mitochondria in the antioxidant-taking group. (Mitochondria are the powerhouses of our cells and their numbers increase with fitness.) Note that they didn’t actually count and compare the numbers of mitochondria in muscle biopsies; they only looked for chemical evidence of increases in mitochondrial ‘growth’.

And here’s where the problems lie:

First and foremost, the bias in this (and other antioxidant-exercise studies) is that ‘taking antioxidants will shortchange your performance gains from exercise’.  Yet, here’s a direct quote from the study’s conclusions: (italics are mine)

“Daily vitamin C and E supplementation attenuated increases in markers of mitochondrial biogenesis following endurance training. However, no clear interactions were detected for improvements in VO2max and running performance. Consequently, vitamin C and E supplementation hampered cellular adaptions in the exercised muscles, and although this was not translated to the performance tests applied in this study, we advocate caution when considering antioxidant supplementation combined with endurance exercise.

So what they’re saying is that despite taking antioxidants, those athletes experienced the same gains in fitness as the placebo group. Yet their conclusion is “… we advocate caution when considering antioxidant supplementation combined with endurance exercise”. Why?

They made that conclusion on not finding chemicals that feed mitochondria. So they’ve associated a lack of biochemical markers responsible for mitochondrial growth with poor performance gains, which weren't recorded at the end of the study! The lack of chemical markers is interesting, but it doesn’t mean anything because we didn’t see it translated to poorer performance.

The researchers didn’t actually compare the numbers of mitochondria in the antioxidant vs. placebo groups (that would be a better study parameter). Yet they caution against the use of antioxidants, even though after 11 weeks of training both groups of athletes were found to be equally fit.

So I guess I’m a little confused, because I’m not seeing how the antioxidants were detrimental to training. And by the way, changes in MaxVo2 are a great way to evaluate gains in fitness.

The second big problem with this study is the theme; antioxidants aren’t meant to be performance enhancers anyway. At least in my mind, I wouldn’t recommend an athlete supplement with them to increase performance - that isn't how they work.

Rather, we recommend antioxidants to limit the overwhelming amount of oxidants that are produced in excessive exercise (such as endurance training. A person who exercises a few times a week really doesn’t need to supplement beyond a healthful diet. However, if you’re training for an ultra run or Ironman, that’s a different story). Antioxidants are useful to limit long-term damage from oxidation, which is cumulatively known as ‘aging’.

A better study would be to measure aging endpoints, such as actual mitochondria counts or perhaps telomere length (which is directly associated with aging and life expectancy).

Don’t let this study scare you away from taking antioxidants. They are important nutrients that offset the negative effects of exercise. And, there are numerous examples of antioxidants protecting against specific oxidant-induced health conditions.

When my training load is heavy, you can bet I’ll still take my antioxidants.

Dr. Jason Barker
Dr. Jason Barker


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