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On the dietary supplement stage, vitamin C is the one-note supporting cast member elevated to stardom. It's got talent, but not nearly enough to match its glorified image and big box-office numbers.
Long touted as a cold-buster and cure-all, vitamin C equals good health in the public imagination like no other nutrient. But scientists are far less enthusiastic in their assessment of vitamin C, which hasn't panned out as a powerful panacea against everything from the common cold to cancer. Despite lukewarm reviews, vitamin C remains one of the most popular supplements on the market.
It's still one of the top sellers in the country,'' says Dr. Michael Hirt, director of the Center for Integrative Medicine at Encino-Tarzana Regional Medical Center.There are spotty areas where vitamin C can be helpful, but not across the spectrum of health like we had hoped.''
Walk into a drugstore and you'll find vitamin C supplements at a range of doses, often starting at 250 milligrams, already more than double the recommended daily allowance of 75 milligrams for women and 90 milligrams for men. Vitamin C also is prominent on the cold medications aisle, where it's packaged as citrus-flavored drops and lozenges.
At best, the nutrient has a modest impact on the severity of symptoms and can shave about a day off the duration of the cold, says Balz Frei, director of the Linus Pauling Institute and professor of biochemistry at Oregon State University.
EARLY HYPE
So how did vitamin C steal the spotlight from the other 12 vitamins essential to human health? Linus Pauling, awarded the Nobel Prize in chemistry in 1954, is credited with giving vitamin C mainstream appeal. In 1970, he wrote a best-selling book called ``Vitamin C and the Common Cold,'' advocating mega-doses of the vitamin. But subsequent research failed to bolster the case.
Linus Pauling was a very smart man and incredibly knowledgeable,'' Frei says.Some of his ideas turned out to be incorrect, and some correct. With respect to the common cold, there's no concrete evidence that vitamin C can prevent it.''
Though vitamin C has been victim to hype, there's no denying that it plays an important role in the body. An antioxidant, vitamin C assists in disease prevention by reversing cell damage caused by unstable oxygen molecules called free radicals. It also helps to produce collagen, a component needed for blood vessels, cartilage, bone and muscle.
Studies on vitamin C's ability to prevent heart disease have been mixed. But in patients already suffering from conditions such as hardening of the arteries, high cholesterol and hypertension, a daily 500-milligram dose of vitamin C helps to dilate blood vessels, which reduces the risk of heart attack and stroke. Vitamin C also decreases the risk of gastrointestinal cancers, Frei says.
We know it's a very good antioxidant and that oxidative stress plays a role in disease,'' he says.The main evidence is really for heart disease and stroke and certain cancers, which are killers in the U.S.''
THE EYES NEED IT
Vitamin C also shows promise in the area of eye health. A recent study by the Johns Hopkins' Wilmer Eye Institute found that taking vitamin C, vitamin E, beta carotene and zinc helped to prevent age-related macular degeneration, the most common cause of blindness in Americans over the age of 60.
There's a potential positive impact on public health that runs a nose in front of the other suggested and studied effects of vitamin C,'' says Dr. Constantine Gean, clinical director of employee health at Valley Presbyterian Hospital in Van Nuys and lead author ofThe Pocket Drug Guide.''
The American Dietetic Association suggests that people get their vitamin C intake by eating at least five servings of fruits and vegetables per day. The powerful mix of antioxidants, phytochemicals and fiber contained in fruits and vegetables is preferred to an isolated supplement, says Bettye Nowlin, a Calabasas-based registered dietitian and association spokeswoman. Green and red peppers, broccoli, oranges, dark leafy greens, and strawberries are all good sources of vitamin C.
Those with greater vitamin C needs - smokers, pregnant women and breast-feeding women - should consider a supplement or fortified foods, Nowlin said.
MIX IT UP
Hirt of Encino-Tarzana is skeptical that Americans will eat the recommended servings of fruit and vegetables - especially since french fries and iceberg lettuce don't count. At the same time, Hirt doesn't recommend vitamin C by itself. He likes to see vitamin C combined with small doses of other antioxidants. The editors of the Berkeley Wellness Letter also recommend an antioxidant supplement of vitamins C and E.
Even if people consume high doses - anything over 1,000 milligrams - the vast majority don't need to worry about toxic effects. Since vitamin C is water-soluble, the body excretes what it doesn't need. The most common fear, the risk of developing kidney stones from regular high doses, only occurs in rare cases, said John Hathcock, vice president of scientific and international affairs for the Council for Responsible Nutrition, a trade organization for the dietary supplements industry in Washington, D.C.
Vitamin C has been the subject of a lot of speculation for adverse effects,'' Hathcock says.Almost all of those have been found in great detail (to be) nonsense.''
Although vitamin C isn't a medical blockbuster, it still plays a valuable role in maintaining good health.
``It's not ready for the nutrition pile of lost, forever-forgotten vitamins,'' Hirt says.
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c.2003 Los Angeles Daily News
