Dec. 14, 2010 (San Antonio) -- More than half of women with breast cancer have low vitamin D levels, British researchers report.
"Women with breast cancer should be tested for vitamin D levels and offered supplements, if necessary," says researcher Sonia Li, MD, of the Mount Vernon Cancer Centre in Middlesex, England. The findings were presented at the San Antonio Breast Cancer Symposium.
Some studies have suggested a link between low vitamin levels and breast cancer risk and progression, but others have not, she says. No studies have proven cause and effect.
Previous research suggests a biologic rationale for vitamin D putting the brakes on breast cancer development and spread, Li 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 cell growth and cause cells to die, she says.
Even if it does not have a direct effect on the tumor, vitamin D is needed to maintain the bone health of women with breast cancer, Li says. That's especially important given the increasing use of aromatase inhibitors, which carry an increased risk of bone fractures, she says.
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.