Vitamins: Separating Fact From Fiction

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Vitamins: Separating Fact From Fiction

Experts cut through the hype about the health benefits of vitamin

supplements By SIne, Reviewed By Louise Chang, MD

There are enough myths around vitamins to make an ancient Greek

blush, and it's easy to see why.

We all know that vitamins and minerals are essential to good health -

- it says so right there on the cereal box. And we live in the more-

is-better era of Hummers, Big Gulps, and McMansions. Which raises

the obvious question: if taking 100% of the Recommended Dietary

Allowance (RDA) of, say, vitamin C is good enough to keep us going

through the day, then why shouldn't taking 1,000% be enough to melt

our fat, cure our blues, and let us leap tall buildings in a single

bound?

Meanwhile, the $19 billion-a-year dietary supplement industry

continually reminds us that we can get our vitamins from a pill.

Which invites yet another question: Why should we bother choking

down bushels of brussels sprouts when we could get the same effect

by sprinkling supplement shavings over our Boston cream pie?

If life were only that easy. The broad consensus from nutrition

experts -- or at least the ones who aren't buying Hummers with the

proceeds from supplement sales -- is that while vitamins are indeed

essential, big doses are usually pointless and can even be harmful.

And no pill is likely to ever adequately substitute for a healthy

diet.

Why They Matter

Why They Matter

Vitamins and minerals are substances your body needs for normal

growth and functioning. Some facilitate crucial chemical reactions,

while others act as building blocks for the body.

Nutritionists call vitamins and minerals " micronutrients " to

distinguish them from the macronutrients such as proteins,

carbohydrates, and fats that make up the bulk of our food. While

micronutrients are vital for the proper processing of

macronutrients, they're needed in smaller quantities. Think of it

this way: If macronutrients are the gas in your engine, then

micronutrients are like the motor oil, coolant, and battery fluid.

Micronutrient deficiency can lead to acute diseases with exotic

names like scurvy, pellagra, and beriberi. Deficiency diseases were

common in the U.S. until the 1940s, when the FDA-mandated

fortification of common foods like bread and milk. These diseases

are still common in many poorer countries.

Maintaining a Healthy Diet

It's easy to get enough micronutrients from your food if you

maintain a healthy diet, Audrey Cross, PhD, associate clinical

professor of nutrition at Columbia's School of Public Health, tells

WebMD. But most people fail that test; they'll eat two or three

servings of fruits and veggies per day rather than the recommended

five. That's why Cross (and many other nutritionists) suggest a

multivitamin as a sort of nutritional safety net for many of their

patients.

But it's just a safety net. So-called " whole foods " like veggies and

whole grains contain fiber and a host of other important nutrients

that can't be adequately delivered through pills. In fact,

scientists are still finding new " trace elements " in whole foods

that may someday be labeled essential to health -- but aren't found

in any pill.

" There are literally thousands of these compounds, and we're just

scratching the surface on knowing what their role is, " says

Grotto, a registered dietitian and spokesman for the American

Dietetic Association. " We're sending the wrong message if people

believe they've got everything under control and if they're taking

vitamins while eating a horrible diet. "

Choosing a Supplement

Choosing a Supplement

It's easy to become overwhelmed when looking at the dietary

supplement shelves of a health food store or even your local

supermarket. While many of the health claims are unproven or

downright bogus, some supplements may be useful for some groups.

Major multivitamin makers typically produce different varieties for

men, women, children and older folks. Picking a pill that fits your

group makes sense, says dietitian Grotto, as the optimal level of

various nutrients varies by age and sex. For example, premenopausal

women need more iron than children or the elderly, he says.

But the elderly have a harder time obtaining adequate amounts of

vitamin B-12 from natural sources, so the need for supplementation

may increase with age, says Lynn , a University of Florida

nutritionist who teaches courses on vitamins.

Folate, or folic acid, is key to preventing birth defects (such as

spina bifida), says. says all women of childbearing

age should ensure they get 100% of the RDA of folic acid through

fortified food or a multivitamin.

Calcium and Vitamin D

Calcium supplements are also important for certain age groups,

says. The Institute of Medicine, part of the National Academy

of Sciences, recommends that adolescents get 1,300 milligrams of

calcium a day. One cup of milk or calcium-fortified orange juice

contains about 300 milligrams of calcium.

Other sources of calcium include cheese, tofu, yogurt, vegetables,

and beans. A typical calcium supplement may contain 500 milligrams

or 600 milligrams of calcium. gives her 15-year-old son a

daily calcium supplement at dinnertime. People over 50 should get

1,200 milligrams a day of calcium to ward off osteoporosis (thinning

of the bones), says.

Federal dietary guidelines recommend that the elderly, the

homebound, and people with dark skin boost their vitamin D intake

with both fortified foods and supplements to reduce the risk of bone

loss. Vitamin D helps with absorption of calcium; often calcium

supplements will also contain vitamin D. (The full federal

guidelines, updated in 2005, are available at

www.health.gov/dietaryguidelines.)

Special groups such as smokers, pregnant women, or people recovering

from traumatic injury may need additional supplements, Cross says.

Decisions to take supplements beyond a multivitamin are best made

with your doctor or registered dietitian, she says.

The evidence is strong that a healthy diet can ward off chronic

diseases like cancer and heart disease. What's less clear is if big

intakes of particular micronutrients can boost that preventive

effect further.

There is promising evidence that the mineral selenium could prevent

a variety of cancers, says Alan Kristal, DrPh, associate chief of

cancer prevention at the Fred Hutchinson Cancer Research Center in

Seattle. But beyond selenium, the data aren't promising, Kristal

says. For example, there's no solid evidence that taking large doses

of antioxidants like vitamins B or C have any beneficial effect.

Controversial Health Claims

Controversial Health Claims

As you seek the proper multivitamin or dietary supplement, it's best

to keep your guard up. The supplement industry is relatively

unregulated, and you can injure or even kill yourself with " natural "

products bought at your neighborhood supplement store.

Many health claims attached to multivitamin formulations are

doubtful, but harmless. Some men's multivitamins contain extra

lycopene, a substance once thought to prevent prostate cancer. But

Kristal, the cancer specialist, says support for that claim is

waning. " If indeed lycopene did anything, [supplements] don't have

enough to make a difference, " he says. Multivitamins aimed at women

are often spiked with green tea or ginseng extract; the effect of

these on weight control is yet unproven.

More dangerous are recommendations of vitamin megadoses to treat

obesity, depression, carpal tunnel syndrome or other problems. At

best, megadoses are a distraction from real treatments for these

problems, experts say. At worst, they can cause injury or death.

So-called fat-soluble vitamins -- that is, vitamins A, D, E, and K --

accumulate in the body, making overdosing a real threat. Vitamin

overdoses have been associated with liver problems, weakened bones,

cancers, and premature mortality.

Until recently, water-soluble vitamins such as B and C were

considered nontoxic, even at high doses. But now evidence is

emerging that B-6 megadoses can cause serious nerve damage,

tells WebMD.

Despite the warnings, the quest for a magic pill plunges ahead.

Cross chuckles when patients show her weight loss supplements that

claim wondrous effects " when taken in combination with a sensible

diet and exercise. " Her response: Wouldn't a sensible diet and

exercise do the trick even without the supplement?

SOURCES: Harvard School of Public Health web site: " Vitamins. " Mayo

Clinic web site: " Vitamin and mineral supplements: Use with care. "

U.S. Department of Health and Human Services: " Dietary Guidelines

for Americans 2005. " Lynn B. , professor of human nutrition,

food science and human nutrition, University of Florida,

Gainesville. Audrey Cross, PhD, associate clinical professor of

nutrition, Mailman School of Public Health, Columbia University.

Grotto, registered dietitian; spokesman, American Dietetic

Association. Alan Kristal, DrPh, professor of epidemiology,

University of Washington; associate director of cancer prevention,

Fred Hutchinson Cancer Research Center.