April 19, 2010 (Washington, D.C.) -- Multivitamins and calcium supplements
may help protect women against breast cancer, new research suggests.
In a study of more than 700 women, taking multivitamin tablets in the
past five years was associated with 31% lower odds of having breast cancer. The
use of calcium supplements was linked to a 40% reduced risk.
The study involved 268 women with breast cancer and 457 women without breast
cancer, all in Puerto Rico. The women filled out detailed questionnaires asking
which supplements they took during the past five years, how frequently they
took them, and whether they still took them.
The women also gave blood samples so the researchers could measure the
ability of their DNA to repair damage, a complex biological process that is
critical to preventing cancer.
The findings were presented at the annual meeting of the American
Association for Cancer Research.
The study showed that older age, reduced DNA repair capacity, a family
history of breast cancer, and not breastfeeding all raised the risk of breast
When DNA repair capacity was taken into consideration, calcium was no longer
protective against breast cancer, suggesting that calcium supplements act to
enhance DNA repair, says Jaime Matta, PhD, professor of pharmacology,
physiology and toxicology at Ponce School of Medicine in Ponce, Puerto
Multivitamins remained protective even after taking into account DNA repair,
however, suggesting it is associated with other anticancer benefits as well, he
Taking supplements of vitamins A, E, or C alone was associated with a
slightly lower risk of breast cancer, but the finding could have been due to
All the analyses were adjusted to take into account the effect of other
breast cancer risk factors such as age, family history, and having been
Matta tells WebMD the finding suggests that vitamins may work better
together than individually to lower cancer risk.
Other studies have had conflicting results. Some have suggested that
supplement forms of single vitamins such as A and E don't protect against
breast cancer. Others have suggested that vitamins are protective.
"The jury is still out," says Victoria Seewaldt, MD, director of the Duke
Early Protection Program at Duke University in Durham, N.C.
The dose and timing may explain the disparity, she tells WebMD. "It could be
that taking high doses later in life gives very different effects than taking
the recommended amount of vitamins earlier on," Seewaldt says. Most of the
women in the study were aged 41 to 60.
One weakness of the study is that the researchers asked women to recall
their vitamin intake instead of measuring vitamin levels in the blood.
Another drawback, Matta says, is that "we don't know the exact dose that
women took. But generally women told us that they took the inexpensive
one-a-day supplements you get at your local drug store."
Also, even though the researchers tried to adjust for risk factors, women
who take supplements may be more likely to engage in behaviors such as eating
right and exercising that are associated with a lower risk of breast
Still, Matta says there's no harm in taking a daily multivitamin. "If it
comes with calcium, even better."
"There's no toxicity at normal doses and it may help protect against
cancer," Matta says.
Seewaldt cautions against making recommendations based on one study
"The importance of the study is that it's addressing normal doses, the
recommended amount of vitamins, not high-dose supplements. It underscores the
role good nutrition plays in cancer prevention," she says.