Vitamin D deficiency may increase the odds that some men who already are at high risk for prostate cancer will have an aggressive form of the disease, according to new research.
The study, published online today in Clinical Cancer Research, is the first to evaluate whether vitamin D deficiency might be associated with prostate cancer based on biopsy results from men who had abnormal findings on a prostate-specific antigen (PSA) test or digital rectal examination. Previous studies compared vitamin D levels only in men with or without prostate cancer.
Investigators enrolled 667 men aged 40 to 79 years who had their first prostate biopsy at 1 of 5 urology clinics in Chicago. About half were African American and the other half were European American. Their blood levels of 25-hydroxyvitamin D (25-OH D) were measured at enrollment to determine vitamin D deficiency.
European American men had higher 25-OH D levels (19.3 nanograms per milliliter [ng/mL] of blood) than African American men (16.7 ng/mL). Dark skin has more melanin, which blocks ultraviolent rays that trigger vitamin D production. The Institute of Medicine has concluded that a 25-OH D level below 12 ng/mL puts a person at risk for vitamin D deficiency and levels from 12 ng/mL to 20 ng/mL indicate insufficiency. But 20 ng/mL is considered adequate for most people.
Overall, 383 men in the study received a prostate cancer diagnosis. Among African American men, those with a 25-OH D level below 20 ng/mL were 2.4 times more likely to be diagnosed with prostate cancer than those with higher levels. African American men with 25-OH D levels below 12 mg/mL were nearly 5 times more likely to have aggressive prostate cancer and 4.2 times more likely to have a tumor stage T2b or higher, meaning that cancer is present in more than half of either the left or right side of the prostate.
Among European American men, 25-OH D levels weren’t related to overall prostate cancer risk. But those with levels below 12 ng/mL were 3.7 times more likely to have aggressive prostate cancer and 2.4 times more likely to have a tumor stage T2b or higher.
In both groups, low 25-OH D levels were linked with aggressive prostate cancer even after investigators accounted for diet, smoking habits, obesity, family medical history, and calcium intake.
“The stronger associations in African American men imply that vitamin D deficiency is a bigger contributor to prostate cancer in African American men compared with European American men,” lead author Adam Murphy, MD, said in a statement.
Murphy, an assistant professor of urology at Northwestern University’s Feinberg School of Medicine in Chicago, said vitamin D supplements may help prevent tumor progression in some men with prostate cancer. “It would be wise to be screened for vitamin D deficiency and treated,” he added.