Vitamins linked to breast cancer
April 18, 2010 - 9:07AM/the AGE
A major study has revealed that women who take a daily multi-vitamin pill are nearly 20 per cent more likely to develop breast cancer.
The shock finding has rattled Australia's $2.5 billion complementary health industry, which is urging consumers not to panic, according to News Ltd reports.
In a 10-year study of more than 35,000 women, researchers discovered those who regularly took a multi-vitamin pill increased the risk of developing a tumour by 19 per cent.
They said the result was concerning and needed investigation as many women use multi-vitamins in the belief they prevent chronic diseases such as cancer. A "biologically plausible" explanation is that taking vitamin and mineral supplements significantly increases the density of breast tissue, a strong risk factor for breast cancer. Folic acid, often present in a potent form in multi-vitamins, may also accelerate tumour growth.
The study, conducted by Sweden's Karolinska Institute and published in the American Journal of Clinical Nutrition, has been greeted with interest and caution by Australian experts. Women who took a multi-vitamin pill in the study had higher breast tissue density than those who took no vitamin supplements.
"Results from this prospective study suggest that the use of multivitamins may increase the risk of breast cancer," the lead author of the study, Susanna Larrson, said.
Karolinska Institutet (often translated from Swedish into English as the Karolinska Institute, and in older texts often as the Royal Caroline Institute) is one of Europe's largest medical universities.
It was founded in 1810 on Kungsholmen island on the west side of Stockholm. Its main campus was moved decades later and located in Solna, just outside Stockholm, and a second campus more recently in Flemingsberg/Huddinge south of Stockholm.
A committee of the institute appoints the laureates for the Nobel Prize in Physiology or Medicine. ...<cont>
The New York Times
May 15, 2008, 2:26 pm
Multivitamins Linked With Breast Density
By TARA PARKER-POPE
Breast density, which is increasingly used as a marker of breast cancer risk, is associated with the use of multivitamins, a new study shows.
Regular mammograms may be especially important in women with dense breasts. (Mary Haggerty/The New York Times)The report, published this month in The American Journal of Clinical Nutrition, raises questions about advice routinely given to women to take a multivitamin. However, because the study is not a randomized clinical trial, it’s not clear if multivitamin use contributes to a woman’s breast density. It may be that the type of woman who takes multivitamins is more likely to have other risks factors linked to dense breasts.
Breast density describes the relative amount of different tissues present in the breast. A dense breast has less fat than glandular and connective tissue. On a mammogram, a dense breast looks mostly white, whereas a fatty breast looks dark gray.
Numerous studies have shown that breast density is an important breast cancer risk factor, and women with extreme density may have a two- to six-fold increased risk of breast cancer. In addition to its role in breast cancer risk, breast density makes it difficult to identify cancer on a mammogram, potentially increasing the risk that cancer will be diagnosed at a later stage.
The latest study, from Quebec researchers, studied multivitamin use among nearly 1,600 women, half of whom had not yet reached menopause. About 22 percent of the women used multivitamin and mineral supplements, and use was almost evenly distributed among women who had or had not reached menopause. Premenopausal women who were currently using multivitamin and mineral supplements had, on average, about 5 percent more breast density than women who had never taken multivitamins, a finding that was statistically meaningful. There were no statistically meaningful differences among those who did or did not use multivitamins after menopause.
The findings don’t mean that women using multivitamins should stop taking them, particularly if their doctors have prescribed the supplements. However, women with dense breasts should be aware of it and seek regular mammograms and possibly additional ultrasound scans. A recent study showed that using ultrasound with mammography helped doctors spot significantly more breast cancers in high-risk women with dense breasts but also resulted in four times as many false alarms
Could Multivitamins Raise Breast Cancer Risk?
Tuesday , March 30, 2010
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.
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. Susanna 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.
Taking certain vitamin supplements may adversely affect people's lifespan, researchers have suggested.
Millions worldwide use antioxidant supplements such as vitamins A and E, and beta-carotene.
Looking at dozens of previous studies, Copenhagen University researchers suggested these appeared to raise, not lower, the risk of early death.
The Copenhagen team reviewed more than 815 clinical trials into the benefits of vitamins A, E, and C, alongside beta-carotene and selenium - all commonly-used supplements.
They selected 68 whose methods were more likely to produce an accurate picture of vitamin benefits, then added their results together to form one, large-scale study.
This overview suggested that taking antioxidant supplements neither increased, nor reduced, the risk of early death.
However, when the researchers eliminated a further 21 trials which had a slightly higher possibility of producing a skewed result, the picture changed considerably.
While the risk of death was unchanged among selenium and vitamin C users, a statistically significant increase in risk emerged for the other three supplements.
Beta-carotene produced an approximate 7% increased risk, vitamin E a 4% increase and vitamin A, a 16% increase.
The researchers wrote: "Our findings contradict the findings of observational studies claiming that antioxidants improve health.
"Considering that 10% to 20% of the adult population in Europe and North America may consume the supplements, the public health consequences may be substantial."
They said there were several different explanations for this increase in risk - and suggested that knocking out 'free radicals' might actually interfere with a natural defence mechanism within the body.
The team called for more research into the effects of vitamin supplements on health.