So this "more antioxidants are better for you" theory? May have holes.

[brooksmoses]

I recently came across this interesting blog post on a medical-chemistry blog I read ("In the Pipeline", by Derek Lowe), which is reporting on a recent paper in Proceedings of the National Academy of Sciences, entitled Antioxidants prevent health-promoting effects of physical exercise in humans (full-text freely available online).

In short, half the test subjects in a four-week exercise program took 1000mg of Vitamin C (that is, one typical large vitamin C pill, though it's about 1200%-1700% of the daily RDA depending on which numbers one uses), and 400 IU of Vitamin E (again, one large supplement pill, 1333% of the daily RDA) per day. The results of comparing the two groups indicated that the "antioxidant supplements appear to cancel out many of the beneficial effects of exercise". In particular, it appears that the oxidants released in the bloodstream by exercise are a key part of the pathway by which exercise affects glucose uptake and insulin sensitivity, and dietary antioxidants block that pathway. This is particularly important with regards to type-II diabetes; those effects of exercise are important to preventing it and can in mild cases even reverse it if it occurs.

Moreover, the blog post references another paper in American Journal of Clinical Nutrition, which "showed that vitamin C supplementation seemed to decrease the development of endurance capacity during an exercise program."

As Derek says, "there's enough evidence to go ahead and say it: exercise and antioxidants work against each other. The whole take-antioxidants-for-better-health idea, which has been taking some hits in recent years, has just taken another big one."

Comments

[prus.livejournal.com]

Interesting. Are there any supposed benefits of antioxidants that exercise cannot give? Or exercise is just better overall? If one really has to spend a hour per day doing exercise-that-is-not-walking, that's disappointing. (Not that I take either vitamic C or E at present)

[eagle]

It's scientifically unclear whether taking more antioxidants than are necessary for basic nutritional needs do anything for you at all. Clearly, you don't want to get scurvy, so there's a certain minimum that you need, but a good diet delivers that relatively easily.

Outside of that, the only truly confirmed scientific research that I've seen says that large doses of vitamin C does mildly reduce the duration (but not the chances of contracting) a cold.

Antioxidants do a lot of things your body related to aging and cell breakdown, but as with anything in nutrition, just because they're very important in your body doesn't mean that you have a deficit or taking in more of them will do more of the good thing.

[prus.livejournal.com]

Just googled on vitamin C and cold -- the reduction of duration by 'half-a-day' is a bit funny. And that's for common cold. Guess I should plan on flu shot next year.

[johnpalmer.livejournal.com]

Well, a lot of cell damage and aging wear-down is oxidation based. So, in theory, reducing oxidation reactions must be reallyreallygood for you.

In theory.

There are circumstances in which antioxidants are good for you. I've been told that a largeish dose of vitamin C helps post-surgical healing, for example.

I'd also heard that vitamin E (2-400 IU, IIRC) helps post exercise muscle healing. Of course, maybe that's part of the point... maybe you don't want to speed that healing up.

I'm only a layman in these matters, though, so I'm not even 100% sure of those two items.

[whispercricket]

Very interesting study. I like to rip journal articles apart, so take the following for what you will.

Paper #1:
1) Very small sample (40 subjects, all "healthy young men") - from looking at their study design, they only ended up with 6 subjects in each of the 4 double-blind placebo-controlled groups.

2) Ascorbic acid and d-alpha-tocopherol aren't the only antioxidants that exist. :} I'd prefer them to be more precise as to what they studied, although I guess "Ascorbic acid and d-alpha-tocopherol lower exercise benefits for type-2 diabetes markers" wouldn't have the same effect. *sigh*

(From what I read, the data on glucose sensitivity was pretty clear, but the data on endogenous antioxidant production showed that at least a couple of them weren't as affected as others, plus they were focusing on diabetes- related benefits overall.)

3) I'm generally pretty picky about the supplements used for these sorts of studies- at least this study states exactly what it uses. For vitamin C, they only used ascorbic acid - there are differences between how the body handles that versus mineral ascorbates versus either + cofactors (bioflavonoids etc.). For vitamin E, they only used d-alpha tocopherol - there have been studies showing that supplementing with alpha-tocopherol can lower gamma-tocopherol, etc., and that we really don't have a clear picture of how the tocopherols / tocotrienols work together.

(Early study on ascorbic acid + cofactors on guinea pigs)

(From my reading on natural supplementation, I've come to the personal conclusion that I'd prefer to take a natural vitamin C supplement in a lower dosage - something based off of amla or camu-camu, for instance - and have sodium ascorbate on hand for higher dosage in the case of suspected viruses or if needing another immune system boost like with vaccinations, with the natural C serving to provide bioflavonoids. Bleeding gums also can be a sign of a subclinical vitamin C deficiency, I believe.)

4) The study does note that there have been conflicting studies previously, and one possible explanation "may be that those studies suggesting an inverse relation between ROS and insulin sensitivity were obtained in models of continuous exposure to increased levels of ROS [...] whereas our current findings and those of other studies [...] may reflect transient increases in ROS during limited periods of physical exercise only."
- So I read this to say that for people with continuous oxidative stress (getting sick, perhaps, or having a chronic condition), the mechanism of ROS -> enhanced body functioning (improved glucose sensitivity + creation of antioxidants) very well may work differently.

So this study does not appear to dispute the fact that antioxidant supplementation may have some uses, especially for people who may not be in condition to get the benefits of aerobic exercise. The assertion that if you're trying to improve your glucose sensitivity, then you want to watch your external antioxidant supplement intake, however, is definitely interesting.

5) In reading the summary, I found it interesting that they stated "Molecular mediators of endogenous ROS defense (superoxide dismutases 1 and 2; glutathione peroxidase) were also induced by exercise, and this effect too was blocked by antioxidant supplementation" - this appears to show that in a healthy body, there is a balance between the potential damage and repair capabilities (which does make some sense if you assume healthy bodies know what they're doing :) ). Since I've seen some references to glutathione at least being helpful for a healthy immune system, it shows that exercise may be able to help you keep from getting sick as well (to be extremely general).

[whispercricket]

Forgot to add that I'm looking at vitamin C supplementation partially because of taking medication that can diminish the body's supply of vitamin C - e.g. as listed at whfoods - so for a reason specific to me, not to all people. :)

(My preference generally is to get necessary vitamins and minerals from foods or at least sourced from foods, since I think there are a lot of synergistic compounds that get left behind when the isolates are lab-created.)

[whispercricket]

And now I've read the abstract for the second study (even smaller sample size than the first study, sadly). Not being a focused exercise supplement type of person, I wasn't aware that people were taking somewhat high supplemental amounts of ascorbic acid specifically to try and counteract some of the (theoretically negative) effects of exercise.

I'm finding it both fascinating and somehow not surprising that basically shortcircuiting the body's internal adaptations to normal physical stress (i.e. exercise) isn't very helpful. :)