In 2010, the National Cancer Institute estimated that more than 200,000 women developed breast cancer with almost 40,000 women dying from the disease. They further estimated that more than 12 percent of women born in 2011 will be diagnosed with breast cancer in their lifetime. Dietary components, such as vitamin D, may reduce this risk.
Vitamin D Sources and Functions
The few sources of naturally occurring vitamin D come from fish, animal products and mushrooms. Most vitamin D comes from fortified foods. Most people get their vitamin D from dairy products, fatty fish or fortified cereals. Exposure to short durations of sunlight also allows the body to produce endogenous vitamin D. Specific recommendations for intake of vitamin D depend on age and other factors like pregnancy. In general, older individuals require more vitamin D than their younger counterparts. Vitamin D classically assists with calcium absorption, which helps to maintain healthy bones. It also helps balance blood calcium and phosphorus levels, which are important in many physiological processes including muscle contraction. Dr. Elizabeth Berton-Johnson from the University of Massachusetts also indicates that vitamin D may modestly reduce your risk of developing breast cancer.
Breast Cancer and Sunlight
Large population-based studies first suggested that where you live impacts your risk of developing some cancers, including cancer of the breast. More cancer cases appear in northern states and fewer cases arise in states with more sunshine exposure. Because sunlight promotes vitamin D exposure in the body, researchers hypothesize that vitamin D may reduce breast cancer incidence. UVB ray exposure inversely correlates with breast cancer risk in women from 107 countries, according to a study by researchers at the University of San Diego. Countries with greater sun exposure report fewer breast cancer cases than countries with less sun exposure.
American Institute for Cancer Research Report
The American Institute for Cancer Research conducted a systematic literature review on the relationship between diet, physical activity and lifestyle on cancer risk. The original report published in 2007 could not establish a relationship between vitamin D and breast cancer risk due to a lack of qualifying studies. An update of the report identified qualified breast cancer studies relating to dietary vitamin D, supplemental vitamin D or blood vitamin D levels. Five studies found no effect of vitamin D on breast cancer risk, one found a negative impact and two reported that vitamin D reduces breast cancer risk.
Vitamin D and Estrogen Receptor Positive Breast Cancer
According to the Mayo Clinic, different breast cancer subtypes exist. The most commonly discussed include estrogen receptor positive and estrogen receptor negative. Estrogen is a sex hormone produced in your body that can activate pathways which may include induction of cancer. Estrogen needs to bind to a receptor in the tissue to activate these pathways. Some breast cancers require estrogen to proliferate, known as estrogen receptor positive breast cancers, while others do not. A study by Blackmore and colleagues reports that vitamin D intake or sun exposure during adolescence and early adulthood reduced the risk of estrogen receptor positive breast tumors.
References
- "American Journal of Epidemiology"; Vitamin D from Dietary Intake and Sunlight Exposure and the Risk of Hormone-Receptor-Defined Breast Cancer; KM Blackmore, M. Lesosky, H Barnett, et al.; June 2008
- Mayo Clinic: Breast cancer types: What your type means
- "The Breast Journal"; Relationship between low ultraviolet B irradiance and higher breast cancer risk in 107 countries; SB Mohr, CF Garland, ED Gorham, et al.; April 2008
- "Annals of Epidemiology"; Vitamin D and Breast Cancer; ER Bertone-Johnson; July 2009
- National Cancer Institute: SEER Stat Fact Sheet: Breast
- American Institute for Cancer Research: Continuous Update Project: View Breast Cancer Report
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