A new study has found that women with breast cancer who lacked vitamin D in their diet had more aggressive cancers than breast cancer patients with healthy levels of vitamin D. The researcher, Dr. Pamela Goodwin, a professor at the University of Toronto Medical School, found that a vitamin D deficiency is common amongst breast cancer patients, especially those with the worst prognoses. Surprisingly, three out of four of the patients had low levels of the vitamin. Goodwin reported that the cancer was more likely to metastasize (spread to other organs), and the patient was more likely to die if she had insufficient vitamin D.

Should breast cancer patients and other women take vitamin D supplements?

Could the chances of improving survival be so simple for breast cancer patients? Not necessarily. This study is the first to report a link between low vitamin D and aggressive breast cancer. It would therefore be premature to recommend more vitamin D for women diagnosed with breast cancer, because there are health risks from too-high levels of the vitamin. Dr. Goodwin is waiting to see if other researchers find the same results before drawing any conclusions.

In Goodwin's study, premenopausal women with low vitamin D levels were also more likely to have a high Body Mass Index (BMI), high blood insulin levels, and diets low in grains. These factors have been independently found to increase cancer risk. It is therefore possible that the risk of breast cancer rose because of these other factors, not because of the lack of vitamin D. However, the opposite is also possible - perhaps women with high BMI tend to have lower levels of vitamin D, for example. Further research is needed to determine if vitamin D predicts more aggressive breast cancer regardless of BMI, insulin levels, or grain consumption.

Vitamin D's role in the body

Unlike most other essential vitamins, our bodies make vitamin D when our skin is exposed to direct sunlight. We can also receive vitamin D when we consume fortified milk and cereals.

Vitamin D helps direct cell growth and differentiation. Dr. Julia Knight, a researcher at Mount Sinai Hospital in Ontario, Canada, found that vitamin D limits the spread of cancerous cells in the breast and helps these cells destroy themselves. In addition, a previous study by Dr. Goodwin suggests a link between a woman's vitamin D deficiency and greater breast cancer risk. She suggests that due to all "[of] these molecular effects, we believe that it is possible that vitamin D circulating in the blood may actually slow the growth and progression of breast cancer." Increased sun exposure and milk consumption in teenage girls decreased breast cancer risk when they were adults. These are both great ways to increase your vitamin D levels. Dr. Goodwin's results did not extend to older women, so she suggests that teenage girls, whose breasts are still developing, should enjoy the sunshine and consume milk in order to raise their vitamin D levels.

Goodwin urges that all women ask their doctors to check their vitamin D levels. Whether or not it is eventually found to reduce the risk of breast cancer, we already know that vitamin D improves women's bone health.


References:

Chustecka, Zosia. "Vitamin D deficiency Linked to Poorer Outcome in Breast Cancer." Medscape Medical News. 17 June 2008. 21 May 2008. Link: http://www.medscape.com/viewarticle/574846.

Goodwin PJ, Ennis M, Pritchard KI, Koo J, and Hood N. "Frequency of vitamin D (Vit D) deficiency at breast cancer (BC) diagnosis and association with risk of distant recurrence and death in a prospective cohort study of T1-3, N0-1, M0 BC." J Clin Oncol: 2008 (May 20 suppl; abstr 511). Link: http://www.asco.org/ASCO/Abstracts+%26+Virtual+Meeting/Abstracts?&vmview=abst_detail_view&confID=16&abstractID=178

Knight JA, Lesosky M, Barnett H, Raboud JM, and Vieth R. "Vitamin D and reduced risk of breast cancer: a population-based case-control study." Cancer Epidemiol Biomarkers Prev. 2007 Mar:16(3):422-9. Link: http://cebp.aacrjournals.org/cgi/reprint/16/3/422.