A growing body of laboratory and animal evidence as well as epidemiological data shows low levels of vitamin D may contribute to certain types of cancer. Conversely, strong biological and mechanistic bases indicate that vitamin D may play some role in the prevention of colon, prostate, and breast cancers.
Vitamin D is essential for promoting calcium absorption for bone and overall health in people. Low levels of vitamin D can lead to rickets in infants and children and the loss of bone density in adults.
More than 25 million adults in the United States have or are at risk of developing osteoporosis, a disease characterized by the loss of bone density that makes bones fragile and significantly increases the risk of fractures. When it comes to Osteoporosis, it’s a chicken and egg scenario: osteoporosis is most often associated with inadequate calcium intakes (generally less than 1,000-1,200 mg/day), but insufficient vitamin D contributes to osteoporosis by reducing the body’s calcium absorption.
While the evidence is far from conclusive, vitamin D may also prove to be an important protective nutrient in the prevention and treatment of cancer.
In a 2008 study, University of Toronto researcher, Pamela Goodwin, MD, and colleagues measured vitamin D levels in the blood of 512 newly diagnosed breast cancer patients (95% of them Caucasian) and tracked the progress of their disease over an average of about 12 years. Women in the study with the lowest levels of vitamin D (deficient) had nearly double the risk of their breast cancer progressing, and had a 73% greater risk of death compared to women with adequate vitamin D levels. The findings were statistically significant, and were not affected by other factors including age, weight, tumor stage, or tumor grade.
The University of Toronto study found about 38% of the women in the study had vitamin D levels low enough to be considered "deficient" and 39% had levels that were "insufficient." Just 24% of the women in the study had "adequate" vitamin D levels.
In another clinical trial conducted by Creighton University School of Medicine researcher Michael Parfitt focused on bone health in 1,179 postmenopausal women residing in rural Nebraska. He found that subjects supplemented daily with calcium (1,400-1,500 mg) and vitamin D3 (1,100 IU) had a significantly lower incidence of cancer over four years compared to women taking a placebo. While Parfitt cautions the small number of cancers reported (50) precludes generalizing about a protective effect from either or both nutrients or for cancers developing at different sites, but he says it shows some promise.
Most recently, the University of Rochester Medical Center researchers studied 166 women undergoing treatment for breast cancer, the majority of these women (70 percent) had more in common than their cancer: they had very low vitamin D blood levels. Those women whose cancer had progressed to late stage or were non-Caucasian had the lowest levels of all.
The researchers set out to study the affects of cancer treatments on women, not a causal relationship between low levels of vitamin D and cancer, but the findings are still significant.
“Vitamin D is essential to maintaining bone health, and women with breast cancer have accelerated bone loss due to the nature of hormone therapy and chemotherapy. It's important for women and their doctors to work together to boost their vitamin D intake,” said Luke Peppone, Ph.D., research assistant professor of Radiation Oncology, at Rochester's James P. Wilmot Cancer Center, and a member of the National Cancer Institute's Community Clinical Oncology Program research base in Rochester. The findings were reported at the 2009 American Society of Clinical Oncology's Breast Cancer Symposium held in San Francisco.
Vitamin D deficiencies include muscle pain, difficulty sleeping, weak bones resulting in fractures, low energy, fatigue, lowered immunity, symptoms of depression and mood swings. What’s more, these symptoms are also commonly seen in women who are undergoing breast cancer treatment with chemotherapy and/or radiation therapy. As such, the experts say women with breast cancer should be given high doses of vitamin D (50,000 international units or more) because a majority of them are likely to have low levels of vitamin D, which could contribute to decreased bone mass and greater risk of fractures.
The Institute of Medicine recommends 200 IU daily for most women up to age 50, 400 IU for women 51-70, and 600 IU for women 71 and older. In addition to availability in pill form, vitamin D is found in small amounts in foods like oily fish (salmon, tuna, mackerel). It is also added to milk, some cereals, and orange juice.
Experts encouraged women to have their vitamin D levels checked as part of their annual checkups. Vitamin D is also achieved naturally through sunlight exposure, although prolonged sun exposure is also linked to skin cancer.
The National Institute of Health Office of Dietary Supplements cautions further research is needed to determine whether vitamin D inadequacy in particular increases cancer risk, whether greater exposure to the nutrient is protective, and whether some individuals could be at increased risk of cancer because of vitamin D exposure. The National Institutes of Health has more information on Vitamin D. http://www.cancer.gov/cancertopics/factsheet/prevention/vitamin-D
Lynette Summerill, is an award-winning journalist who lives in Scottsdale, Arizona. In addition to writing about cancer-related issues, she writes a blog, Nonsmoking Nation, which follows global tobacco news and events.
“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.” Presented at the 2008 annual meeting of the American Society of Clinical Oncology. First author: Pamela Goodwin, University of Toronto.
Parfitt AM. Osteomalacia and related disorders. In: Avioli LV, Krane SM, eds. Metabolic bone disease and clinically related disorders. 2nd ed. Philadelphia: WB Saunders, 1990:329-96.
The effect of high-dose vitamin D supplementation on 25-OH vitamin D levels in breast cancer patients during treatment. Meeting: 2009 Breasy Cancer Symposium- Abstract No. LBA211 First Author L.J. Peppone.
Reid IR. The roles of calcium and vitamin D in the prevention of osteoporosis. Endocrinol Metab Clin North Am 1998;27:389-98. [PubMed abstract]