Benefits of vitamin supplements questioned

[Guest guest]

http://www.stuff.co.nz/stuff/print/0,1478,3676360a7144,00.html

TUESDAY , 23 MAY 2006

Americans may be taking too many vitamin supplements in the hope of

staying healthy and living longer, a panel of US experts have said.

Some people clearly need supplements, the panel said - for instance,

older women benefit from taking calcium and vitamin D to strengthen

their bones, and younger women need to take folic acid to reduce birth

defects in any children they may have.

But no studies show strongly that people prosper from popping

multivitamin and mineral supplements and some suggest that eating

healthily and exercising provide more benefit, the panel said.

" Half of American adults are taking multivitamins and minerals and the

bottom line is that we don't know for sure that they're benefiting

from them, " said Dr J McGinnis, a senior scholar with the

Institute of Medicine, who chaired the panel.

" In fact, we're concerned that some people may be getting too much of

certain nutrients, " added McGinnis, whose organisation advises the

federal government on health issues.

The 13-member panel included experts in nutrition, biostatistics,

biochemistry, toxicology, geriatric medicine, family medicine,

pediatrics, cancer prevention, consumer protection and other fields.

They said much more study was needed on what vitamins Americans lacked

in their diets and whether taking supplements provided actual benefit.

Many people may assume that because vitamins and minerals are vital

for health, that more is better. But some are toxic at high levels,

including vitamin A and iron, and others are simply excreted in the

urine.

Beta-carotene was shown in a surprise study to raise the risk of lung

cancer in smokers.

The panel said anti-oxidant vitamins and zinc might help nonsmoking

adults with early stage, age-related macular degeneration, which can

cause blindness.

But many foods are fortified with vitamins and minerals, so the value

of supplements is often questioned.

There are no good studies showing people who take multivitamin or

mineral supplements can prevent chronic diseases such as cancer and

heart disease.

Many of the studies that suggest a protective effect also show that

people who take vitamins tend to take care of their health in other

ways, such as eating plenty of fruits and vegetables, exercising and

not smoking, so it is difficult to determine whether the vitamins were

responsible for health benefits.