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Study: Vitamin D May Influence Breast Cancer Outcome (dateline June 7, 2008)

Women diagnosed with breast cancer who have vitamin D deficiencies are more likely to have poorer outcomes compared to those with normal vitamin D levels, according to the results of a new study. Specifically, the researchers found that breast cancer patients without enough vitamin D were more likely to be diagnosed with higher grade tumors. They were also more likely to experience a recurrence of breast cancer or die from the disease, compared to women with normal vitamin D levels. The research suggests that getting enough vitamin D in the diet may be important to fighting breast cancer.

The recommended daily intake of vitamin D is 400 international units (IU). Vitamin D may be obtained from vitamin-D fortified milk and foods such as liver, fish, and egg yolks. Vitamin D supplements or a multiple vitamin that contains 400 IU of vitamin D are also good sources. Sunshine on the skin also helps the body make Vitamin D. Generally, 15 minutes of sun exposure per day is enough to maintain sufficient Vitamin D levels. However, factors such as weather, latitude, time of year, etc. may influence absorption. One of benefits of vitamin D is that is promotes the absorption of calcium, which is essential for good bone health.

According to researcher Dr. Pamela J. Goodwin from Mount Sinai Hospital at the University of Toronto, vitamin D deficiencies are common in breast cancer patients. Dr. Goodwin spoke at a press conference in advance of the study's release at the annual meeting of the American Society of Clinical Oncology. At the press conference, Dr. Goodwin noted that, "There is a growing knowledge in the basic biology of breast cancer that demonstrates that breast cancer cells have vitamin D receptors in their nuclei and that activation of those receptors by vitamin D can change the molecular machinery of the cell to slow down the growth of the cell and cause differentiation." Dr. Goodwin suggested that vitamin D can help remove the aggressiveness from some breast cancers.

In her study, Dr. Goodwin and her colleagues examined 512 women who were diagnosed with early-stage breast cancer between 1989 and 1995. The researchers followed the women for about 12 years. The women were given a survey about their diet and blood samples were taken at the time of their diagnosis.

According to the study, the risk of breast cancer spreading outside the breast to other areas of the body was nearly twofold (1.94) for women who had vitamin D deficiencies at the time of their breast cancer diagnosis, compared with women with normal vitamin D levels. In addition, the researchers found that the risk of death was 75% higher (a 1.73-fold increased risk) for the women with deficient vitamin D levels. The researchers also observed an increased risk of death among women with vitamin D levels that were too high (above 400 IU), although they note that these findings warrant further study.

The researchers say that it is too soon to recommend that women take vitamin D supplements that are higher than what is already recommended for bone health-about 400 IU. However, Dr. Goodwin noted that breast cancer patients might want to have their vitamin D levels checked. If there is a deficiency, Dr. Goodwin suggests that a patient would want to take steps to ensure that she eliminates the deficiency with vitamin supplements.

Additional Resources and References

  • The study referenced in this article was presented at the annual meeting of the American Society of Clinical Oncology in May 2008. See