Vitamin D and cancer. Most of us have gotten the message about protecting our skin from too much sun exposure. But in slathering on sunscreen to reduce the risk of one cancer, are we depleting our stores of vitamin D – a vitamin that might protect us from other cancers?
The medical community hasn’t reached a collective agreement on the issue. Some studies have found a link between vitamin D deficiency and increased risk for breast cancer, as well as colon cancer and even non-Hodgkin’s lymphoma, while other studies have found no connection. This spring, researchers published findings in the journal Endocrinology linking vitamin D deficiency with increased risk that breast cancer will spread outside the breast (metastasize).
Research is ongoing, although it is difficult to pinpoint a link between vitamin D and cancer, in part because levels of the vitamin change in the body and because dietary studies can’t quantify how much vitamin D people get from sunshine. But Rocky Mountain Cancer Centers oncologist Hyun Sue Kim, MD, isn’t waiting for a definitive decision; she’s making sure her Colorado Springs breast cancer patients get plenty of the essential vitamin D, and of calcium.
“I’ve always been very aggressive about maintaining patients’ bone health,” Kim says. She carefully monitors vitamin D levels, because the association between low vitamin D and greater breast cancer risk is fairly well established. “We wish we knew the mechanism – we don’t yet – but studies have shown people with good bone health have less breast cancer and have fewer recurrences of breast cancer,” Kim says.
She initially began checking vitamin D levels in her patients because the body needs it to deliver calcium to the bones. Her findings weren’t what she expected: Most patients’ calcium levels met recommended goals, but vitamin D deficiency was common. “We are closer to the sun because of our high altitude, so I was surprised when I checked vitamin D – only a few women were at recommended levels without supplements.”
The Institute of Medicine recommends 600 “international units” per day of vitamin D up to age 70, and 800 units after age 70. Most supplements come in doses measured by international units.
It’s not hard to surmise why so many women are deficient in vitamin D, which we primarily obtain from sun exposure, Kim says. “We are mostly indoors now. Few of us work outside. And even if we are outdoors, we put on so much sunscreen, we aren’t getting vitamin D.”
Kim isn’t advising people to run out and bake themselves in the sun. There are plenty of other sources, including fatty fish, fish oil, and milk and other dairy products that have been fortified with vitamin D. And, she recommends supplements. “I tell people to take 2000 to 5000 international units a day,” she says. While the link is still being researched, vitamin D might just be another weapon in the fight against cancer.