SUNSHINE VITAMIN: A lack of vitamin D, which we get from sunshine, may play a significant role in breast cancer.

A new study sponsored by the Breast Cancer Research Foundation found a clear connection between vitamin D levels in breast cancer patients and the likelihood of their cancer spreading (metastasizing) or causing death. While it looks like women deficient in vitamin D were at increased risk of cancer progression, doctors warned against taking vitamin D supplements until more research proves its benefit.

Which Came First: Vitamin D Deficiency or Breast Cancer?

Doctors analyzed 512 women from Toronto, averaging age 50, who had been diagnosed with breast cancer between 1989 and 1995. Each woman had had blood drawn and stored at the time of diagnosis and had answered a questionnaire about her diet. Using radioimmunoassay (a technique to find antibody levels) to measure vitamin D, doctors monitored the women for almost 12 years. No patient received vitamin D supplements during the study.

At the time of their breast cancer diagnosis:

• 37.5% of women were deficient (lowest levels) in vitamin D
• 38.5% had insufficient (between deficient and healthy) levels of vitamin D
• 24% had healthy (optimal) levels of vitamin D

Women who were deficient in vitamin D at the time of their diagnosis were:

• 94% more (almost twice as) likely to have their cancer metastasize than those with healthy vitamin D levels
• 73% more likely to die within 10 years of their diagnosis
• But women with insufficient levels of vitamin D did not differ in survivability from those with healthy levels.

The study reports that ten years after they’d found out they had breast cancer:

• 83% of those with adequate vitamin D levels at the time of diagnosis were still alive
• 79% of those who’d had insufficient vitamin D at the time of diagnosis were still alive
• 69% of those who were deficient in vitamin D at the time of diagnosis were still alive

Though not statistically significant, the risk of cancer spreading or death may be slightly increased for women with excessive vitamin D levels. "This suggests that there's a healthy level for vitamin D and, if you are deficient, you have an increased risk of metastasis, but if you go above [a certain point], your risk of death goes up again," said study author Dr. Pamela Goodwin, a medical oncologist with Mount Sinai Hospital and a professor of medicine at the University of Toronto. (Health Day, 5/16/08)

Among the study participants, low vitamin D levels were common to women who were premenopausal, weighed more, and had high insulin levels and more aggressive tumors. To explain why those with more weight had low vitamin D, Goodwin said fat tissue acts as a trap for the sunshine vitamin, keeping the chemical from being used by and detected in the body.

Vitamin D and Breast Cancer: Not Such a Surprising Relationship

Earlier research has suggested that vitamin D levels may be linked to breast cancer risk. "We know from basic science studies that breast cancer cells have vitamin D receptors and can interact with vitamin D," Goodwin said. (Health Day, 5/16/08)

Other researchers have observed vitamin D blocking the formation of new tumor-feeding blood vessels and interfering with abnormal cell growth. Previous studies have suggested that vitamin D may play a role in preventing prostate and colon cancer.

Too Soon to Supplement with Vitamin D

Each year, about 1.15 million women around the world, including 215,000 in the United States, develop breast cancer. Globally, 410,000 die from it each year. In the United States, breast cancer kills 41,000.

Still, experts warned that it’s too soon to recommend vitamin D supplements as a general treatment for breast cancer. “We don’t want to see women taking 10,000 IU a day,” Goodwin said. (Reuters, 5/15/08).

Copyright © 2010 Informify

Sources

Low Levels of Vitamin D Spell Trouble for Breast Cancer Patients (Health Day, 05/16/08)

Vitamin D deficiency linked to breast cancer, study finds (Los Angeles Times, 05/16/08)

Vitamin D may lower breast cancer risk (Reuters, 05/15/08)

Question for Readers:

Which do you think comes first—vitamin D deficiency or breast cancer? Or do you think the two work together in some kind of feedback loop?