In the early 2000s, Rick Kittles, a geneticist at the City of Hope in Duarte, California, was curious about a study from researchers in the United Kingdom, who had found a link between prostate cancer and skin pigmentation. Men who had high-tanning pigmentation (meaning their skin was darker in color) were twice as likely to get prostate cancer as Caucasians who had little variation across their skin tone.
“I thought that if that’s the case, we should see something astonishing in black men,” recalls Kittles. The work inspired him to study the relationship between vitamin D, pigmentation, and prostate cancer.
Although it’s called the “sunshine vitamin” because sunlight converts vitamin D to its active form in the skin, vitamin D is actually a steroid hormone, which means it heads straight for the nucleus and locks onto DNA, turning genes on and off. Its anti-cancer properties may come from vitamin D’s ability to help the body fight inflammation. “The ability [of the body] to get rid of bad cells is also impacted by vitamin D levels,” says Kittles. Studies across the world show that darker-skinned people who lived in higher latitudes where the sun isn’t out all year are more prone to vitamin D deficiencies. And African-American men who live in areas like Chicago, where they are exposed to less sunlight, have higher rates of prostate cancer. For now the link between vitamin D and prostate cancer is still an association, not a smoking gun. Researchers don’t know how or if a deficiency may cause prostate cancer.
Arul Chinnaiyan, director of the Michigan Center for Translational Pathology, says, “Some think, ‘If it does no harm, try it,’ but scientifically there isn’t enough compelling evidence to say that anybody should take that particular vitamin for [prevention of] prostate cancer.”
Kittles puts himself firmly in the vitamin D camp. His own physician recommended that Kittles take 5000 IU per day of vitamin D after Kittles moved to Chicago in 2008 and became deficient. And even though he lives in California now, he still takes the same amount because he’s indoors so much.
“Vitamin D regulates itself so much in the body that you can’t overdose,” says Kittles. “You can go to CVS or Walgreens and get [bottles of] 5000 unit-pills for six dollars.”
If you are considering taking vitamin D to try and prevent prostate cancer, talk it over with your doctor first.