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Antioxidants Are Good, Free Radicals Are Bad, Right?


Health & Wellness  (tags: cancer, diet, disease, environment, food, health, humans, illness, medicine, nutrition, prevention, research, risks, protection, safety, science, study, drugs, exercise, society, treatment, death, AlternativeMed, healthcare )

Michael
- 972 days ago - montrealgazette.com
One thing we know for sure about antioxidants, those superheroes that wage war against evil free radicals that conspire to rob us of our health and youth, is that they sell products. Unfortunately what we don't have is compelling evidence to support them.



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Michael O. (172)
Saturday January 21, 2012, 8:03 am
by Joe Schwarcz, Director of McGill University's Office for Science and Society (OSS.McGill.ca)

There is one thing we know for sure about antioxidants. They sell products. Unfortunately that is just about the only thing we know for sure about this fascinating class of chemicals. In the public mind, though, antioxidants are superheroes that wage war against those evil free radicals that conspire to rob us of our health and our youth. And according to a variety of marketers, the antioxidants that are naturally present in our food supply are not enough to protect us from the free radical onslaught. We need reinforcements in the form of whatever pill, capsule or potion they have concocted. And these usually come with plenty of testimonials about lives turned around. But what they do not come with is compelling evidence.

The story usually goes something like this: We need oxygen to live. Any student who has studied glycolysis and the dreaded Krebs cycle will recall the critical role that oxygen plays in the production of cellular energy. Basically, glucose reacts with oxygen to yield carbon dioxide, water and energy. But there are also some by-products. These are the notorious free radicals, also referred to as "reactive oxygen species." And they are reactive. Should they take aim at important biomolecules, such as proteins, fats or nucleic acids, they can wreak molecular havoc.

Our body, however, doesn't just stand by as the electron deficient free radicals try to satisfy their hunger for electrons by ripping essential molecules apart. It musters its defences. And those defences are the "antioxidants," a wide array of compounds linked by the ability to neutralize reactive oxygen species. They encompass enzymes such as superoxide dismutase, vitamins A, C and E, and various "polyphenols" derived from plant products in our diet. Since plants produce oxygen through photosynthesis, they have had to evolve protective mechanisms to deal with oxidation. We can benefit from the antioxidants they churn out. So far, so good.

Populations that consume more fruits and vegetables are healthier. That is also more or less correct. But why is this the case? The seductive argument is that produce is loaded with antioxidants and that these chemicals are responsible for the health benefits by scavenging free radicals. A simple formula emerged: Free radicals are bad, antioxidants are good. And the marketers ran with that one. Fast enough to blur the facts.

Any substance that demonstrated antioxidant properties in the laboratory became a quasi drug. Shelves sagged under the weight of exotic juices, green tea and pine bark concoctions, various carotenoids and of course vitamins C and E. The contest was on for the antioxidant championship. Products vied with each other to claim the highest "oxygen radical absorption capacity," or ORAC rating. ORAC is a measure of the ability of a sample to neutralize free radicals in a test tube. But the body is not a giant test tube, and ORAC values do not necessarily translate into biological significance. Many polyphenols that can put on an impressive antioxidant performance in the test tube may not even be absorbed from the digestive tract.

Vitamins C and E, along with beta carotene, readily wiped out free radicals in lab experiments and became the poster boys for antioxidant supplements. But when researchers got around to carrying out clinical studies, the results were disappointing. Most found no benefit. One actually showed an increase in lung cancer risk in smokers taking beta carotene supplements. Some studies even claimed an increased risk of premature mortality in people who regularly supplemented with antioxidants. Could it possibly be that free radicals are not the villains they have been made out to be? As is so often the case in science, issues that seem straightforward on the surface become more complicated with a little digging. So let's dig a little.

It turns out that white blood cells generate and unleash free radicals in their fight against bacteria and viruses. So clearly, in the right quantities, at the right time, free radicals can be health-enhancing. Furthermore, the production of free radicals for such defence purposes is sensed by other cells that then fire up their internal defences and produce enzymes such as catalase and superoxide dismutase that can deal with larger amounts of potentially dangerous free radicals. Sort of like exposure to a small amount of toxin prompts the system to deal with larger insults.

One interesting theory suggests that antioxidants in food may actually work by generating health-promoting quantities of free radicals. When an antioxidant neutralizes a free radical by donating an electron, it itself becomes a free radical, but a potentially much less damaging one. Still, it might be threatening enough to stimulate the body's own antioxidant defences. Antioxidant supplements might not work as well as antioxidants in food because the doses are too high, and they may suppress free radical formation excessively. Sounds farfetched? Well, consider this:

It is well known that exercise improves insulin sensitivity, which in turn helps manage Type 2 diabetes. But exercise also increases the formation of reactive oxygen species as cells gear up to generate the energy needed. In a German study, 40 healthy young men were given an exercise regimen to follow for four weeks. Half the subjects were asked to take a daily supplement of 1,000 mg of vitamin C and 400 IU of vitamin E. Surprisingly, insulin sensitivity improved only in those not taking the supplements! Furthermore, production of superoxide dismutase and glutathione peroxidase, the enzymes that protect against free radicals, was increased by exercise, but again only in the subjects not taking the supplements. It seems that the free radicals produced by exercise-induced oxidative stress provide the signal for increased insulin sensitivity and for revving up antioxidant defences. The researchers concluded "that supplementation with antioxidants may preclude these health-promoting effects of exercise in humans." I think I'll stick to getting my antioxidants from my daily five-to-seven servings of fruits and vegetables.

Life sure is complicated. There are no simple solutions. As H.L. Mencken said, "For every complex problem there is a solution that is simple, neat and wrong." And the relationship of diet and supplements to health is indeed a complex problem.
 

Carmen S. (611)
Saturday January 21, 2012, 11:43 am
noted, thanks Michael for this information
 
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