At this morning’s Gastrointestinal Cancers Symposium in San Francisco, California, researchers from Harvard Medical School introduced data showing that Vitamin D levels correlate well with a colon cancer patient’s survival.
Dr. Kimmie Ng, assistant professor of medicine at Dana-Farber Cancer Institute and Harvard Medical School, looked at blood levels of vitamin D in 300 colorectal cancer patients and found that higher vitamin D levels predicted improved survival. She was able to confirm these observations with another 1,000 patients. Metastatic, stage IV patients also showed low levels of vitamin D.
At this time, it is unclear whether the correlation between vitamin D blood levels and colon cancer survival is causal, implying that vitamin D supplementation could be used therapeutically. Of course until a link is established, there are few disadvantages in consuming recommended vitamin D supplementation for existing colon cancer patients. Under the supervision of a doctor, patients should discuss the ramifications of consuming vitamin D supplements in dosages above the current recommended dietary allowance (RDA).
The National Academy of Sciences’ Institute of Medicine established the RDA of vitamin D in children and adults at 600 IU per day, almost 3 times its previous levels, and raised the upper intake level for adults from 2,000 IU to 4,000 IU per day. Excess vitamin D does carry a risk of hypercalcemia, but studies at Harvard and other institutions have found that doses as high as 10,000 IU per day is well tolerated in healthy adults. In a 2007 study, researchers at Harvard argued in the paper “The urgent need to recommend an intake of vitamin D that is effective” that “vitamin D consumption by adults should be 10,000 IU per day. This indicates that the margin of safety for vitamin D consumption for adults is >10 times any current recommended intakes.”
Vitamin D is obtained through foods or sunlight exposure, specifically ultraviolet-B radiation (UVB). Black patients are at increased risk of lower Vitamin D levels, primarily because of increased melanin content in their skin which blocks vitamin D synthesis from UVB radiation exposure. People who live in countries above the 37th parallel are also at risk of lower vitamin D levels simply because they don’t get as much sun exposure, especially during the winter months.
Oregon State University researcher Jane Higdon, PhD, writes that “very little, if any, vitamin D can be synthesized in the skin from November through February at latitudes north of 37 degrees in the Northern Hemisphere.” This area north of San Francisco and Virginia includes most of the the United States and Japan, and all of Canada and Europe.
Vitamin D has been implicated in many cancers as a chemopreventive, a therapeutic, and a survival predictor. The vitamin’s role in the immune system and the calcium cycle is well documented. In 2014, researchers also correlated vitamin D levels with dementia, noting that those “severely deficient” had a 125% increased risk of dementia.