In my search for information regarding Vitamin C and its negative effect on the kidneys, I came across this interesting article:
Vitamin C? Gene damage?
How do you make sense of the research?
Bad studies may be more dangerous than vitamins...
Does Vitamin C Really Damage DNA?
Commentary © 1998 by Jack Challem, The Nutrition Reporterô
Updated on April 12, 1998
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First, it was beta-carotene. Now it's vitamin C. Next it will probably be vitamin E.
The question: are dietary supplements safe?
A study in the April 9, 1998, journal Nature (1) reported that 500 mg of vitamin C daily causes damage to DNA, the complex protein that forms your genes. Gene damage makes people edgy because it sometimes leads to cancer.
But all of the headlines could just as well have stated that vitamin C supplements prevented DNA damage. That's because the same study also found that vitamin C did that as well.
Confused? You should be! Almost every week, you're pulled in contrary directions with positive and negative studies on vitamins, drugs, and most other things.
Take the beta-carotene studies. They showed that long-term smokers had a slightly greater risk of developing lung cancer if they took beta-carotene supplements. But the same data also found that smokers had better lung function with beta-carotene, and that former smokers had a lower risk of lung cancer with beta-carotene.
Another analysis of the data found that beta-carotene reduced the risk of prostate cancer among these smokers, but only if they didn't drink alcohol. If they did drink, the beta-carotene increased the risk of prostate cancer.
All this soon starts to sound like a Three Stooges routine, with supplements being good if you take them on Tuesdays under a full moon while standing on one foot. But if you take them on Wednesdays under a half moon while standing on both feet, forget it.
That brings me, in a circular way, back to the vitamin C study.
This study, which has alarmed so many people, was described as "scientific correspondence" ≠ essentially, a letter to the editor ≠ in Nature. The researchers measured only two of the 20 markers of free radical damage to DNA. We have no idea how vitamin C affected the other 18 markers of DNA damage.
If we applied the same standard of DNA damage to foods we regularly eat, we would probably ban hamburgers, hot dogs, steaks, sausages, bacon, and ham sandwiches. That's because cooking meat generates chemicals called heterocyclic amines, well documented for their ability to damage DNA.
Bruce N. Ames, Ph.D., of the University of California, Berkeley, has often pointed out that about half of all chemicals, natural and synthetic, cause DNA damage. He notes that naturally occurring compounds in alfalfa sprouts (canavanine), broccoli (isothiocyanate), potato (solanine), celery (psoralen), and onion (quercetin), and most fruits and vegetables cause DNA damage.
But no one warns us to stay away from such foods because their benefits far outweigh their risks. And, as Ames has also pointed out, the body's DNA repair enzymes ≠ which are largely dependent on the B vitamins ≠ fix nearly all of the damage.
The totality of the scientific evidence supports the view that relatively high levels of vitamin C are good for health and relatively low levels are bad for health.
Just about any cell biologist or biochemist will tell you that every antioxidant ≠ of which vitamin C is one ≠ becomes a weak free radical (or pro-oxidant) when it quenches free radicals, molecules known to damage and break DNA and set the stage for cancer and coronary heart disease.
But, as Lester Packer, Ph.D., also of the University of California, Berkeley, has frequently pointed out, antioxidants also work as a team and recycle each other back to full-bodied antioxidants, ready to scour more free radicals.
Still other researchers have reported that high doses of vitamin C protect against DNA damage in blood cells, eye lenses, and sperm. Some studies have even shown that too little vitamin C causes DNA damage.
Balz Frei, Ph.D., director of the Linus Pauling Institute at Oregon State University, Corvallis, has pointed out that other studies directly contradict the findings of the Nature study.
Furthermore, Frei, Ames, and Packer quickly went on record criticizing the Nature study's methodology. Ames, one of the most distinguished scientists in the world, bluntly called it "bad science."
We could have a tug of war with every new study. After all, it's easy to marshal evidence in support of one theory or another. Scientists do it all the time.
But I have a better idea. Let's just slow down, get a few more facts, and provide a larger context for such research. Otherwise, we're doomed to always have six studies of one view and six of another ≠ and no way to make sense of any of them.
(1) Researchers at the University of Leicester, England, gave 30 healthy subjects 500 mg of vitamin C daily for six weeks. They measured the DNA in peripheral blood lymphocytes for damage. They noted a significant increase in 8-oxoadenine levels, a marker of DNA damage and a significant decrease in 8-oxoguanine levels, another (and better established) marker of DNA damage. Podmore ID, et al., "Vitamin C exhibits pro-oxidant properties," Nature, April 9, 1998;392:559.
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