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Thursday June 14 3:11 PM ET

Vitamin C Found to Promote Cancer-Causing Agents

By Will Dunham

WASHINGTON (Reuters) - Vitamin C, an essential nutrient found in fruits and vegetables and taken in large doses by many people as a dietary supplement, is a double-edged sword, providing benefits but also inducing the production of compounds associated with cancer, researchers said on Thursday.

Researchers at the University of Pennsylvania added vitamin C, also known as ascorbic acid, to solutions of a degraded version of an important fatty acid found in blood, and found that it triggered the production of DNA-damaging agents known to cause mutations associated with a variety of cancers.

Lead researcher Ian Blair of the university's Center for Cancer Pharmacology cautioned that the study was conducted in a test tube and not with living human cells or in actual people.

``Absolutely for God's sake don't say vitamin C causes cancer,'' Blair said in a telephone interview.

``The key finding is that vitamin C can do good things and bad things. And we've figured out what the bad ones are. In terms of the impact, I think it just redirects people's attention to the fact that you can't replace a good diet with magic bullets such as vitamin C.''

The value of vitamin C has been the subject of a long and heated debate in the scientific community. One of the leading scientists of the 20th century, Linus Pauling, who died at age 93 in 1994, championed it as a tool for fighting cancer.

But skeptics argued that numerous studies have found that vitamin C produced no benefit in combating cancer, and that taking supplements actually could have negative consequences. The new study appears to add weight to those concerns.

CAUTION URGED ON DIETARY SUPPLEMENTS

``Far more caution should be taken in the use of dietary supplements -- and an insistence on real proof that there's a benefit before undertaking any of them,'' said Dr. Arthur Grollman, director of the Laboratory for Chemical Biology at the State University of New York at Stony Brook.

``The real, serious implication is that it (vitamin C) could contribute to DNA damage that could cause cancer,'' added Grollman, an expert in cancer causes who was not involved in the study. ``It just adds more evidence that there could be a significant risk to ascorbic acid.''

Blair said the study, which appears in the journal Science, may explain why vitamin C has shown little effectiveness at preventing cancer in clinical trials.

Vitamin C is a water-soluble vitamin that is important for bone and connective tissue growth, wound repair and the function of blood vessels. It is abundant in citrus fruits, green peppers, tomatoes, cabbage and potatoes. The recommended U.S. adult dietary allowance for vitamin C is 60 milligrams daily. Most supplements contain many times that amount.

Dr. Garret FitzGerald, director of the University of Pennsylvania's Center for Experimental Therapeutics, pointed to evidence of a benefit from an overall healthy diet rather than taking supplements on any particular nutrient.

``We have very clear evidence that eating a diet rich in vegetables and fruits is a healthy thing in terms of it being associated with a reduced incidence of cancer and, indeed, heart disease, for that matter,'' FitzGerald said.

``On the one hand, I would say to people there's no evidence to stop taking vitamin C on the basis of these observations at this point in time. On the other hand, I'd say consider very carefully what the evidence is for taking vitamin C, which is nonexistent. The better part of valor is: save your money.''

VITAMIN C IS AN ANTIOXIDANT

Vitamin C acts as an antioxidant protecting against damage by ``free radicals'' -- highly reactive ions produced by the breakdown of oxygen in cells. In addition to damaging DNA directly, free radicals also can act indirectly.

They begin by converting linoleic acid, the major polyunsaturated fatty acid in human blood plasma and the key polyunsaturated fatty acid in certain cooking oils, into another compound called a lipid hydroperoxide.

When certain metal ions are present as catalysts, the compound degrades into DNA-damaging agents called genotoxins, which cause mutations that have been found in human tumors.

Blair said he had a hunch that vitamin C might be capable of changing lipid hydroperoxides into genotoxins. He added vitamin C to test tube solutions of lipid hydroperoxides, using concentrations comparable to those found in the human body if a person were taking 200 milligrams a day.

The study found that vitamin C was more than twice as efficient as transition metal ions at inducing the formation of genotoxins, including a particularly potent variety.

-- (in@health.news), June 15, 2001

Answers

I don't know if anyone remembers Adelle Davis. She wrote a number of books, beginning, perhaps, with Let's Eat Right to Keep Fit. She was convinced that her diet would not only provide a healthy body, but resistance to cancer. She was pretty devastated when she was diagnosed with cancer, and died from that disease.

I must admit that I adhered to some of her theories for several years. Actually, I still sear liver instead of cooking it for a long time, at her recommend. Her recommends on millet and wheat germ also gave me boundless energy. It wasn't until one friend asked, "Anita, are you still eating health foods?" that I reconsidered her dietary recommendations. This friend said that I was getting REALLY skinny.

Moderation in everything seems to be the key in maintaining a healthy weight and a healthy body. Supplements can help if one isn't obtaining enough in the diet, but vitamins and minerals need to be balanced like everything else. Too much of one and not enough of another can cause problems.

-- Anita (Anita_S3@hotmail.com), June 15, 2001.

The reaction to this study shows how failing to place observations in their proper context can lead to unsound conclusions.

The article states that free radicals convert linoleic acid to lipid hydroperoxides (Step One), and that Vitamin C can convert the latter into genotoxins (Step Two). But it also states that Vitamin C inhibits free radicals from causing damage.

So putting two and two together, Vitamin C, by inhibiting free radicals from producing hydroperoxides, indirectly prevents the formation of genotoxins. Therefore, assessing the net effect of Vitamin C on genotoxin production requires comparing its ability to inhibit Step One against its ability to promote Step Two.

For example, if taking a given amount of Vitamin C would inhibit free radical damage by a factor of ten, then its net effect is to greatly reduce, not increase, genotoxin production.

-- David L (bumpkin@dnet.net), June 15, 2001.

By the way, the reference to "reaction to this study" which starts my previous answer is directed at the "experts" quoted in the article, and not at Anita.

-- David L (bumpkin@dnet.net), June 15, 2001.

Word, Anita, word!

-- Billy Ray (the@phantom.mullet), June 16, 2001.

David--

I take it you are not alarmed by this data. I've taken 3 grams/day of C since 1975 and it hasn't killed me yet. Has it helped? I don't know. I don't get many colds but then I'm not around kids every day either.

What do you think of grape seed extract?

Anita--

I remember Adelle Davis. I think she died in her early 60s? Remember Jim Fixx?

-- Lars (larsguy@yahoo.com), June 16, 2001.

Lars: I don't think I've ever heard of Jim Fixx. I still have my original paperback copy of Adelle's Let's Eat Right to Keep Fit. It's yellowed with age, but is in good shape. I think of her every time I eat black olives. My second daughter and I can go through an entire can of black olives in one sitting. They offer absolutely nothing, nutritionally, but we enjoy the taste.

-- Anita (Anita_S3@hotmail.com), June 16, 2001.

Since the men in my family all tend to die of heart disease, and vitamin C promotes vascular health and inhibits plaque formation (hardening of the arteries), I guess I'll stick with it and take my chances with cancer.

-- Little Nipper (canis@minor.net), June 16, 2001.

"Remember Jim Fixx?"

Started the jogging craze. Died in his mid-forties I think. The poor guy's obituaries were just dripping with irony supplied by overfed, underexercised reporters.

-- Miserable SOB (misery@misery.com), June 16, 2001.

Lars,
I've read that grape seed extract is an antioxidant and is also good for the cardiovascular system. I probably have a reference sitting around, I just can't put my hands on it at the moment.

I remember Jim Fixx. It is often noted that despite his earnest pursuit of health (including lots of running), he died of heart disease in his early fifties. But it is rarely noted that he outlived many of his relatives by at least ten years. So he actually did much to offset a very unfavorable genetic makeup.

-- David L (bumpkin@dnet.net), June 16, 2001.

Lars, indeed I am not alarmed by this data. Based on the observations I shared earlier, the practical significance of this study is zilch.

-- David L (bumpkin@dnet.net), June 16, 2001.

David--

I'm not going to sweat the C either until there is much more data. There is so much fad in all this nutritional stuff, in all directions.

How do Eskimos survive for example. Traditional Eskimo diet must be very low on green veggies and very high on fats. Of course, I have no idea of the life expectancy of traditional Eskimos.

I have taken 200 mg of grape seed extract daily, for the last 4 years. Who knows? I have already outlived me dad by 5 years but have 22 years left to outlive his older brother. My dad was an alcoholic, his brother did not drink.

I am a moderate consumer.

-- Lars (larsguy@yahoo.com), June 16, 2001.