Friday, January 25, 2008

Antioxidants - do more harm than good?


This one is really going to sound heretical.

While we are often told to eat lots of veggies, red tea, green tea and chocolate to benefit from their antioxidants. In the past I've pointed to a couple of studies (here and here) that raised some questions about the supposed benefits of antioxidants in the diet.

This week I've spotted two new studies that indicate that taking supplementary antioxidants - including the popular Vitamin C - can actually interfere with your body's own antioxidant processes - especially in the context of exercise. Maybe chalk up another one for the high fat, low carb boys?

Here are the abstracts:

Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance
Background: Exercise practitioners often take vitamin C supplements because intense muscular contractile activity can result in oxidative stress, as indicated by altered muscle and blood glutathione concentrations and increases in protein, DNA, and lipid peroxidation. There is, however, considerable debate regarding the beneficial health effects of vitamin C supplementation.

Objective: This study was designed to study the effect of vitamin C on training efficiency in rats and in humans.

Design: The human study was double-blind and randomized. Fourteen men (27–36 y old) were trained for 8 wk. Five of the men were supplemented daily with an oral dose of 1 g vitamin C. In the animal study, 24 male Wistar rats were exercised under 2 different protocols for 3 and 6 wk. Twelve of the rats were treated with a daily dose of vitamin C (0.24 mg/cm2 body surface area).

Results: The administration of vitamin C significantly (P = 0.014) hampered endurance capacity. The adverse effects of vitamin C may result from its capacity to reduce the exercise-induced expression of key transcription factors involved in mitochondrial biogenesis. These factors are peroxisome proliferator–activated receptor co-activator 1, nuclear respiratory factor 1, and mitochondrial transcription factor A. Vitamin C also prevented the exercise-induced expression of cytochrome C (a marker of mitochondrial content) and of the antioxidant enzymes superoxide dismutase and glutathione peroxidase.

Conclusion: Vitamin C supplementation decreases training efficiency because it prevents some cellular adaptations to exercise.



Moderate exercise is an antioxidant: Upregulation of antioxidant genes by training.

Exercise causes oxidative stress only when exhaustive. Strenuous exercise causes oxidation of glutathione, release of cytosolic enzymes, and other signs of cell damage. However, there is increasing evidence that reactive oxygen species (ROS) not only are toxic but also play an important role in cell signaling and in the regulation of gene expression.

Xanthine oxidase is involved in the generation of superoxide associated with exhaustive exercise. Allopurinol (an inhibitor of this enzyme) prevents muscle damage after exhaustive exercise, but also modifies cell signaling pathways associated with both moderate and exhaustive exercise in rats and humans.

In gastrocnemius muscle from rats, exercise caused an activation of MAP kinases. This in turn activated the NF-kappaB pathway and consequently the expression of important enzymes associated with defense against ROS (superoxide dismutase) and adaptation to exercise (eNOS and iNOS). All these changes were abolished when ROS production was prevented by allopurinol.

Thus ROS act as signals in exercise because decreasing their formation prevents activation of important signaling pathways that cause useful adaptations in cells. Because these signals result in an upregulation of powerful antioxidant enzymes, exercise itself can be considered an antioxidant. We have found that interfering with free radical metabolism with antioxidants may hamper useful adaptations to training.


So don't take that Vitamin C - exercise itself is an antioxidant and taking antioxidants prevents useful benefits to training! I told you it was heresy!

I have said before that:

It is also worth pointing out that Vilhjalmur Stefansson lived for years on the traditional Eskimo diet of fat and meat....no veggies.......and was, like the Eskimos he was living with, exceptionally healthy. Gary Taubes in his new and excellent book Good Calories, Bad Calories suggests that scurvy and other vitamin deficiency diseases are actually only found when people are eating diets low in meat, eggs and dairy. It seems to be the high levels of carbs that prompt the need for all the vitamins in the veggies.....

12 comments:

rnikoley said...

I'm going to try to get a post up this weekend about how fasting (2 x 30-hr per week) has completely and totally altered my appetite.

The short version: If I just listen to my own body, i.e., what I desire, it's meat and fat. I have lost all appetite for fruit. I do still like salads, but with blue cheese dressing. Veggies, a bit. Nuts, if they're around, but what I find myself craving are huge rib steaks or prime rib, and I now enjoy eating whatever strip of fat it might come with.

CR said...

There's actually a fair amount of research accumulating that taking large amounts of individual antioxidants is not only not helpful, it can be harmful So this may be heresy, but it seems to be backed up by the science.

There was that study a few years ago, for instance, that showed an increase of cancer when taking beta-carotene and vitamin A.

I think that in 10 years we're going to be shocked by the difference between what we think is healthy and what is actually is healthy.

CR said...

"I'm going to try to get a post up this weekend about how fasting (2 x 30-hr per week) has completely and totally altered my appetite...The short version: If I just listen to my own body, i.e., what I desire, it's meat and fat."
--rnikloey

Interesting, and there are a couple of ways to interpret that. One, that you have re-tuned your internal messaging system, and you are getting better messages, and receiving them more clearly.

The other is that your body is famished, and needs to rebuild with macro amounts of macro nutrients. And it's saving it's calories for rebuilding, not for protecting what it already has.

I'd hope (and lean towards) for the former, but be concerned about the latter. So it will be interesting to see what happens over time.

Are you building muscle at the same time?

Chris said...

CR - thanks for the comments.

"I think that in 10 years we're going to be shocked by the difference between what we think is healthy and what is actually is healthy."

I think you are right. Maybe the heretics will come out on top!

Chris said...

Richard - thanks for dropping by.

I must admit that when I first stated eating low carb / paleo I was keen to ensure that I got lots of salads and fruit. As time has gone on meat and eggs (especialy the yolks!) have really become the staples of my diet, with a few veggies and little fruit. Not sure if IF has contributed to this shift or not!

Richard Nikoley said...

CR:

Well, a bit of history is in order. I began this quest last May, with average BP reaings in the 150-160 / 95 - 105. Scary. at 5'10" and 230 pounds, my body fat was probably more than 30%. I began pushing weights (short; very intense) and watched the carbs a bit. I got stronger and bigger quickly, and my BP dropped within a couple of weeks to the 130-140 / 85-95 range, and has continued so that now I'm normal whenever I test.

By October I had lost about 6 or 7 pounds net, and that's when I got more serious about Art's style of eating. Lost a few more pounds. By Christmas I had discovered IF, and since the first of the year have lost about 10 pounds net while getting stronger virtually every workout.

I do intend to back off the fasting a bit once I get my body fat down, and then I'll overfeed a bit on the non-fast days to make up for the deficit.

But all in all, I feel strong, much lighter, high energy, my gluttonous appetite that got me so fat is gone completely, I look forward to and really enjoy the clarity of the fasts, I sleep like a baby, more hours than since I was a teenager.

I'm turning 47 in a few days and for the first time in 20 years I am 100% confident I'm going to regain my youthful physique without any health compromises I can see. Quite the contrary, I think. It's a wonderful place to be, for me, and I'll all because of guys like Art, Chris here, Mark Sisson, Rob Wolfe, Brad Pilon, and all right here on the web, where honesty and reality can finally be asserted over hype, fad, and marketing.

Anonymous said...

One of the good things about fasting that I found is that it really eliminates my desire for carb-rich food. After 20+ hours of fasting, I naturally go the meat way. You can put chocolate cake in front me and I wouldn't even think to touch it.

chalacuna said...

Our body is like a machine the more we use it, the faster it wears out. We should take care of our body with proper diet and exercise.

But sometimes we are taking in toxins unconciously through the air we breath and our food intakes. We have to drink antioxidants to expel these harmful chemicals.


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It's a matter of common sense: an excess of antioxidants may harm you so regulate it's amount is the wise option.

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