Low vitamin D has been linked to everything from heart disease to osteoporosis. Now research suggests vitamin D deficiency may be related to more aggressive forms of breast cancer. We asked Dr. Deanna Attai, chair of the communications committee and member of the board of directors for the American Society of Breast Surgeons, what women should take away from the latest research.
Women who are low on vitamin D have the most serious breast cancer cases. “Researchers looked at some of the molecular biology of the tumors, and what they found was that the woman who were vitamin D deficient had more aggressive tumors and higher recurrence rates,” Attai says. Previous studies have noted an association between the incidence of breast cancer and low vitamin D, but this study is the first to make a connection between deficiency and a poorer prognosis.
African-American women may be at higher risk than other women. In January, a team of University of North Carolina researchers conducted a study on breast cancer patients, and found that 60 percent of the African-American women were vitamin D deficient, compared to only 15 percent of white women. A similar correlation was detected in the ASBS study. The link is not surprising, since our primary source of vitamin D is sunlight, and the pigmentation in darker skin can block absorption. “One of the theories on why we’re seeing more vitamin D deficiency is that everybody is sunscreening to death, but that’s reducing skin cancer, so more sun exposure is not necessarily the answer,” Attai says.
Diagnoses of vitamin D deficiency are increasingly common, but still controversial. In the ASBS study, which involved only breast cancer patients, 18 percent of participants were classified as vitamin D deficient, while another 32 percent had what were considered “insufficient” levels. The Centers for Disease Control and Prevention has estimated that more than one-quarter of Americans have insufficient vitamin D levels. But some critics say the recommended levels of vitamin D are arbitrary, and may be setting the bar too high and encouraging unnecessary supplementation. “There are a lot of doctors who are still pooh-poohing, and saying it’s just the latest thing,” Attai says. But she advises that it’s worth bringing the matter up with your doctor and asking to have your levels checked, especially if you have other risk factors for breast cancer.
Increasing your vitamin D intake is not a cure-all. In recent years, studies have linked low vitamin D to an increased risk of osteoporosis, cardiovascular disease, asthma and a variety of cancers. But while it’s relatively easy to supplement your intake, don’t make think that excuses you from adopting other cancer-fighting lifestyle habits. “This is just one piece of the puzzle,” says Attai. “Just because you supplement vitamin D, it’s not a substitute for a good healthy diet, maintaining a healthy weight or going for your regular screening mammograms.” She adds that no evidence has yet shown that “super” levels of vitamin D offer any special health benefit—so don’t overdo it.