Vitamin D deficiency is a particular problem in individuals with skin of color, and screening of these patients should be considered given the growing list of diseases associated with the condition, said Dr. Grimes at the annual meeting of the American Academy of Dermatology.
African Americans have an increased incidence of many of the diseases also linked to vitamin D deficiency, including hypertension, diabetes, obesity, aggressive prostate and breast cancer, lupus, tuberculosis, and non-Hodgkins lymphoma, said Dr. Grimes.
Vitamin D deficiency has been shown to be associated with numerous other conditions, including neurocognitive disorders, such as Alzheimer's disease, and dermatologic disorders, such as atopic dermatitis, psoriasis, malignant melanoma, and other skin cancers.
In a recent study of 194 African American men undergoing risk assessment for prostate cancer, mean 25-hydroxyvitamin D (25[OH]D) serum concentrations were 13.7 ng/ml (BMC Public Health 2009;9:191). A concentration lower than 20 ng/ml is considered deficient; concentrations of 21-50 ng/ml are considered insufficient; and concentrations of greater than 50 ng/ml are considered sufficient.
More than 60% of the men in the study had levels less than 15 ng/ml; even 55% of the men ingesting more than 400 IU of vitamin D daily had levels less than 15 ng/ml, said Dr. Grimes, a clinical professor of dermatology at the University of California, Los Angeles. She noted the finding raises the question of whether there is a genetic, racially-induced polymorphism that predisposes African Americans to vitamin D deficiency.
Other studies from around the world have also demonstrated racial and gender differences in regard to vitamin D levels, with significantly lower levels found in African Americans and women.
In a study of 185 patients, Dr. Grimes and her colleagues found the highest vitamin D levels were seen in whites, and the lowest were in those with skin of color. Women had slightly lower levels than men. Sun exposure appeared to be a factor, with about 40% of patients using sunscreen regularly, and most only getting sun exposure on weekends.
Sun exposure is the best source of vitamin D, accounting for 80% to 90% of vitamin D levels, compared with 10% to 20% for dietary intake, said Dr. Grimes. The use of a sunscreen with an SPF of 15 can decrease vitamin D production by 99%.
The problem of vitamin D deficiency has increased over time, perhaps due in part to improved photoprotective and sun-avoidance behaviors. Data from the Centers for Disease Control's National Health and Nutrition Examination Survey (NHANES) found that 25(OH)D concentrations decreased in all ages, both genders, and all racial and ethnic groups between 1988 and 2001, she said. "In patients with [25(OH)D] less than 20 ng/ml, I invariably put them on 2,000 IU of vitamin D daily and have them come back in 3-4 months to check their levels," Dr. Grimes said.
Vitamin D3, the natural form of vitamin D when exposed to sunlight, is superior to vitamin D2, which can be found in a select group of foods, said Dr. Grimes. Doses of up to 5,000 IU are also acceptable.
Patients should be advised about the best sources of dietary vitamin D, including fish liver, fish liver oil, fatty fish like salmon (wild is better than farm raised), egg yolks, and milk, she noted. Also, in patients with skin of color, it may be important to weigh the low risk of developing skin cancer against the risks of vitamin D deficiency.
"It is imperative that we educate patients … I think we need to have a dialogue regarding sunscreen," Dr. Grimes said. If a patient with pigmented skin is using an SPF 75 sunscreen, the wisdom of that should be questioned, as should the value of advising more outdoor activity and sun exposure.
"I don't have the answers … but as clinicians we have to think about these things as we move forward," she said.
Dr. Grimes reported she had no disclosures related to her presentation.