Healthy diet from whole fruits & veg, not just vitamins in them

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February 17, 2009

WELL

Vitamin Pills: A False Hope?

By TARA PARKER-POPE

Ever since the Nobel Prize-winning biochemist Linus Pauling first

promoted " megadoses " of essential nutrients 40 years ago, Americans

have been devoted to their vitamins. Today about half of all adults

use some form of dietary supplement, at a cost of $23 billion a

year.

But are vitamins worth it? In the past few years, several high-

quality studies have failed to show that extra vitamins, at least in

pill form, help prevent chronic disease or prolong life.

The latest news came last week after researchers in the Women's

Health Initiative study tracked eight years of multivitamin use

among more than 161,000 older women. Despite earlier findings

suggesting that multivitamins might lower the risk for heart disease

and certain cancers, the study, published in The Archives of

Internal Medicine, found no such benefit.

Last year, a study that tracked almost 15,000 male physicians for a

decade reported no differences in cancer or heart disease rates

among those using vitamins E and C compared with those taking a

placebo. And in October, a study of 35,000 men dashed hopes that

high doses of vitamin E and selenium could lower the risk of

prostate cancer.

Of course, consumers are regularly subjected to conflicting reports

and claims about the benefits of vitamins, and they seem undeterred

by the news — to the dismay of some experts.

" I'm puzzled why the public in general ignores the results of well-

done trials, " said Dr. Eric Klein, national study coordinator for

the prostate cancer trial and chairman of the Cleveland Clinic's

Glickman Urological and Kidney Institute. " The public's belief in

the benefits of vitamins and nutrients is not supported by the

available scientific data. "

Everyone needs vitamins, which are essential nutrients that the body

can't produce on its own. Inadequate vitamin C leads to scurvy, for

instance, and a lack of vitamin D can cause rickets.

But a balanced diet typically provides an adequate level of these

nutrients, and today many popular foods are fortified with extra

vitamins and minerals. As a result, diseases caused by nutrient

deficiency are rare in the United States.

In any event, most major vitamin studies in recent years have

focused not on deficiencies but on whether high doses of vitamins

can prevent or treat a host of chronic illnesses. While people who

eat lots of nutrient-rich fruits and vegetables have long been known

to have lower rates of heart disease and cancer, it hasn't been

clear whether ingesting high doses of those same nutrients in pill

form results in a similar benefit.

In January, an editorial in The Journal of the National Cancer

Institute noted that most trials had shown no cancer benefits from

vitamins — with a few exceptions, like a finding that calcium

appeared to lower the recurrence of precancerous colon polyps by 15

percent.

But some vitamin studies have also shown unexpected harm, like

higher lung cancer rates in two studies of beta carotene use.

Another study suggested a higher risk of precancerous polyps among

users of folic acid compared with those in a placebo group.

In 2007, The Journal of the American Medical Association reviewed

mortality rates in randomized trials of antioxidant supplements. In

47 trials of 181,000 participants, the rate was 5 percent higher

among the antioxidant users. The main culprits were vitamin A, beta

carotene and vitamin E; vitamin C and selenium seemed to have no

meaningful effect.

" We call them essential nutrients because they are, " said Marian L.

Neuhouser, an associate member in cancer prevention at the Fred

Hutchinson Cancer Research Center in Seattle. " But there has been a

leap into thinking that vitamins and minerals can prevent anything

from fatigue to cancer to Alzheimer's. That's where the science

didn't pan out. "

Everyone is struggling to make sense of the conflicting data, said

Andrew Shao, vice president for scientific and regulatory affairs at

the Council for Responsible Nutrition, a vitamin industry trade

group. Consumers and researchers need to " redefine our expectations

for these nutrients, " he said. " They aren't magic bullets. "

Part of the problem, he said, may stem from an inherent flaw in the

way vitamins are studied. With drugs, the gold standard for research

is a randomized clinical trial in which some patients take a drug

and others a placebo. But vitamins are essential nutrients that

people ingest in their daily diets; there is no way to withhold them

altogether from research subjects.

Vitamins given in high doses may also have effects that science is

only beginning to understand. In a test tube, cancer cells gobble up

vitamin C, and studies have shown far higher levels of vitamin C in

tumor cells than are found in normal tissue.

The selling point of antioxidant vitamins is that they mop up free

radicals, the damaging molecular fragments linked to aging and

disease. But some free radicals are essential to proper immune

function, and wiping them out may inadvertently cause harm.

In a study at the University of North Carolina, mice with brain

cancer were given both normal and vitamin-depleted diets. The ones

who were deprived of antioxidants had smaller tumors, and 20 percent

of the tumor cells were undergoing a type of cell death called

apoptosis, which is fueled by free radicals. In the fully nourished

mice, only 3 percent of tumor cells were dying.

" Most antioxidants are also pro-oxidants, " said Dr. Peter H. Gann,

professor and director of research in the department of pathology at

the University of Illinois at Chicago. " In the right context and the

right dose, they may be able to cause problems rather than prevent

them. "

Scientists suspect that the benefits of a healthful diet come from

eating the whole fruit or vegetable, not just the individual

vitamins found in it. " There may not be a single component of

broccoli or green leafy vegetables that is responsible for the

health benefits, " Dr. Gann said. " Why are we taking a reductionist

approach and plucking out one or two chemicals given in isolation? "

Even so, some individual vitamin research is continuing. Scientists

are beginning to study whether high doses of whole-food extracts can

replicate the benefits of a vegetable-rich diet. And Harvard

researchers are planning to study whether higher doses of vitamin D

in 20,000 men and women can lower risk for cancer and other chronic

diseases.

" Vitamin D looks really promising, " said Dr. JoAnn E. Manson, the

chief of preventive medicine at Brigham and Women's Hospital and an

investigator on several Harvard vitamin studies. " But we need to

learn the lessons from the past. We should wait for large-scale

clinical trials before jumping on the vitamin bandwagon and taking

high doses. "

http://www.nytimes.com/2009/02/17/health/17well.html