Vitamin D Deficiency—Role in Breast Cancer Disparities?

Over the next week or so, students from Dr. Olivia Carter-Pokras's EPIB 623 Class (Epidemiology of Health Disparities) will be guest blogging on various topics in the discipline of health disparities. Their insights are well-researched and well-written, and we'll be tagging them for easy access with a new "Health Disparities" tag on the sidebar to your right.

Today, Bethany Applebaum, a second year doctoral student in the Department of Anthropology, will offer insights into Vitamin D Deficiency.
----

In the United States, health disparities are well documented in the African-American population. One specific example is vitamin D deficiency.

The Office of Dietary Supplements at the National Institutes of Health reports that people with darker skin, particularly African Americans, are at greater risk of vitamin D deficiency. This is due to higher levels of melanin in the skin, which is the pigment that gives skin its color. The high melanin content in darker skin, while serving as a protective agent from the sun, reduces the skin’s ability to produce vitamin D from sunlight.

Vitamin D is a unique because it can both be ingested through foods and also produced in our skin when we are exposed to ultraviolet B radiation from sunlight. It is found naturally in only a few foods such as fish oil, egg yolks, and beef liver, but has other dietary sources--including dairy products, cereals and breads--have been fortified to include the vitamin. If exposed to enough sunlight, people do not need to consume vitamin D in their diets—and yet, the majority of people in the United States do not have enough consistent exposure to sunlight to receive the recommended intake of vitamin D suggested by the USDA.

For a detailed description of how vitamin D is metabolized and used in the body, please see this article by Dr. Michael F. Holick in the New England Journal of Medicine.

However, a March 2009 study compared vitamin D levels from the Third National Health and Nutrition Examination Survey (NHANES III), collected during 1988 through 1994, with NHANES data collected from 2001 through 2004 (NHANES 2001-2004).

The study showed that the current recommendations for vitamin D supplementation are insufficient and that racial/ethnic disparities have persisted. A new memorandum of understanding with the National Center for Health Statistics supports similar analyses by faculty and students at the University of Maryland School of Public Health.

The 2010 Dietary Guidelines for Americans have not yet been published but should consider this information. In addition, research efforts and recommendations to figure out how to decrease vitamin D deficiency in the African-American population should be made.

As can be seen in the links above, research has shown that Vitamin D deficiency can have several health implications including skeletal conditions (osteoporosis, osteomalacia), certain cancers, rickets, diabetes, and hypertension to name a few.

Of particular interest is the relationship between vitamin D deficiency and breast cancer. The National Cancer Institute (NCI), a component of the National Institutes of Health (NIH), estimates that 1 in 8 women born today will be diagnosed with breast cancer at some time in their lives.

Incidence and mortality rates, however, vary across race/ethnicity. In their snapshot of breast cancer, NCI reports that while the rate of breast cancer incidence is higher among Caucasian women than among African-American women, African-American women have a higher mortality rate from breast cancer than Caucasian women. African-American women are also more susceptible to early-onset breast cancer than are Caucasian women.

Current research seeks to explore the relationship between vitamin D deficiency and early-onset, aggressive breast cancer in African-American women. Such research has the potential to eventually lead to predictive models of breast cancer and could provide people with the knowledge on how to modify certain behaviors to decrease their risk of breast cancer.