Study: Could multivitamins / supplements raise breast cancer risk?

[Guest guest]

Has anyone seem this yet?

Hmmm. I wish that it was as easy as easy 'as eating a healthy and varied diet'.

P xo

http://www.reuters.com/article/idUSTRE62S4F520100329

Could multivitamins raise breast cancer risk?

Amy Norton

Mon Mar 29, 2010 2:17pm EDT

NEW YORK (Reuters Health) - Many people take multivitamins in the hopes of

thwarting disease, but a new study finds that older women who use multivitamins

may be more likely than non-users to develop breast cancer.

Health

The study, reported in the American Journal of Clinical Nutrition, points only

to an association between multivitamin use and breast cancer. It does not prove

that the supplements directly contribute to the disease.

However, the researchers say, it's biologically plausible that multivitamins

could have such an effect, and the potential link " merits further

investigation. "

The findings come from a decade-long study of more than 35,000 Swedish women who

were between the ages of 49 and 83 and cancer-free at the outset. Over an

average of 10 years, 974 women were diagnosed with breast cancer.

Researchers found that women who reported multivitamin use at the study's start

were 19 percent more likely than non-users to develop breast cancer. That was

with factors like age, family history of breast cancer, weight, fruit and

vegetable intake, and exercise, smoking and drinking habits taken into account.

Still, the large majority of multivitamin users did not develop breast cancer

during the study period. Of 9,017 users, 293 were diagnosed with the disease, as

were 681 women among the 26,000-plus who did not use multivitamins.

And while the study points to a generally higher risk of breast cancer among

multivitamin users as a whole, the risks to any individual woman would likely be

small.

" If the association is causal, using multivitamins would have a modest effect on

breast cancer risk for any one woman, " lead researcher Dr. na C. Larsson,

of the Karolinska Institute in Stockholm, told Reuters Health in an email.

But given the widespread use of multivitamins, any potential risks are of " great

public health importance, " the researchers say.

In the U.S., for example, it's estimated that half of adults routinely use a

dietary supplement, often a multivitamin. And studies show that one of the

primary motivations is the belief that supplements will protect them from

chronic diseases.

But a recent study of more than 160,000 older U.S. women found that over eight

years, those who took multivitamins were no less likely than non-users to die of

heart disease or cancer, with all cancers lumped together in a group.

The current study included more than 35,000 women who were surveyed about their

multivitamin use, as well as a number of other health and lifestyle factors.

It's possible, according to Larsson, that factors the study did not measure

could explain the association between multivitamins and breast cancer.

On the other hand, there are biologically plausible reasons that multivitamins

themselves could be to blame, the researcher said. A recent study found that

among premenopausal women, multivitamin users tended to have greater breast

density than non-users -- meaning the breasts have relatively less fat and more

glandular and connective tissue. Greater breast density is linked to a

relatively higher risk of breast cancer.

It's not clear from that study, however, whether multivitamins themselves

somehow boost breast density.

Another possibility, according to Larsson's team, could be the B vitamin folic

acid, which animal research has linked to breast cancer. Human studies, however,

have come to various conclusions; while one found a higher risk of breast cancer

among women who took folic acid supplements, others have linked the vitamin to

either no effect on breast cancer risk, or a decreased risk.

Since multivitamins are, by definition, a mix of vitamins and minerals, it is

difficult to pinpoint which nutrient, of combination of nutrients, may be

particularly tied to breast cancer risk, the researchers point out.

Until more is known, a woman's best bet is to get her vitamins and minerals from

a well-balanced diet rather than pills, Larsson advised.

" If you eat a healthy and varied diet, " she said, " there is no need to use

multivitamins. "

SOURCE: American Journal of Clinical Nutrition, online March 24, 2010.