Vitamin D Deficiency Worsens Breast Cancer?
Inadequate Levels of Vitamin D Linked to Sharply Increased Odds of Cancer Spread, Death
May 16, 2008 -- Vitamin D deficiency is common among women diagnosed with breast cancer, and it may raise
the risk of cancer spread and death, researchers report.
In a new study, women with vitamin D deficiency at the time of breast
cancer diagnosis were 94% more likely to experience cancer spread and 73%
more likely to die over the next 10 years, compared to women with
adequate vitamin D levels.
More than 1 in 3 women studied had a vitamin D deficiency.
The study is the first to suggest a link between vitamin D deficiency and
breast cancer progression, but it doesn't prove cause and effect. And it's too
soon to recommend that all women with breast cancer start taking supplements to improve their outlook, says study head
Pamela Goodwin, MD, professor of medicine at the University of Toronto.
But "women with breast cancer may want to get their vitamin D levels
checked in a blood test and get them into the healthy optimal range," she
The findings are scheduled to be reported at the annual meeting of the
American Society of Clinical Oncology in Chicago.
Vitamin D Puts Brakes on Breast Cancer
Vitamin D is found in some foods, especially milk and fortified cereals, and
is made by the body after exposure to sunlight. It is necessary for bone
health, and some studies suggest that it may protect women from developing
breast cancer in the first place.
From a biological point of view, it makes sense that vitamin D would put the
brakes on breast cancer development and spread, Goodwin says.
"Breast cancer cells have vitamin D receptors, and when these receptors
are activated by vitamin D, it triggers a series of molecular changes that can
slow down cell growth, cause cells to die, and make the cancer less
aggressive," she says.
For the new study, Goodwin and colleagues measured vitamin D levels in the
blood of 512 women diagnosed with breast cancer in Toronto between 1989 and
1995. They were followed for a median of 12 years.
Only 24% had adequate levels of vitamin D when they were diagnosed with
cancer. A total of 37.5% were deficient in vitamin D. The other 38.5% had
insufficient levels of vitamin D.
Of note, Goodwin says, is that women with vitamin D deficiency were more
likely to have aggressive cancers than those with sufficient levels.
Vitamin D Deficiency Linked to Poor Breast Cancer Prognosis
After 10 years, 83% of women with adequate levels were alive without signs
of cancer spread (metastasis) vs. only 69% of women with vitamin D deficiency.
Most of the deaths were from breast cancer.
For women with insufficient levels of vitamin D, there was a slightly
increased risk of cancer spread compared to women with sufficient levels, but
the difference was so small it could have been due to chance. "And their
risk of death was the same," Goodwin says. "So the majority of the
[negative] effect is in women with a deficiency."