We know from previous studies that if your physician diagnoses you with breast cancer, colon cancer, prostate cancer or lung cancer, higher vitamin D levels at the time of diagnosis are associated with a better prognosis. No one knows about the leukemias, at least until Dr. Xavier Thomas and colleagues in France looked at vitamin D levels in 105 patients with various hematological malignancies. These included acute myeloid leukemia, acute lymphoblastic leukemia, chronic myeloid leukemia, myelodysplastic syndrome and multiple myeloma.
What did they find? In the words of the authors, “In conclusion, 25(OH)D deficiency appeared very common in hematological malignancies since only 28% of the patients studied were 25(OH)D sufficient. The lowest blood levels appeared related to active stages of the disease, poor response to therapy, and therefore aggressiveness of the disease.” That is, higher 25(OH)D levels appear to have a treatment effect in the leukemias.
It is important to remember, as vitamin D supplements are rare in France, that this was a study of leukemias and sunlight. People who don’t take vitamin D supplements, 90% of vitamin D levels come from sun exposure. When sunlight strikes the skin, it makes about ten vitamin D-like compounds in the skin, but vitamin D is the only compound that scientists have studied. We simply don’t know what the nine other compounds do, if anything. However, it is likely that vitamin D supplements will achieve much the same effect as sunlight, given the thousands of test tube studies showing its effectiveness.
One last thing. In all these studies of vitamin D levels in diagnosed cancer, people with high vitamin D levels still died, although they took longer to do it. That is, it seems unlikely that vitamin D will cure cancer; although it may do so in some cases. In this study, patients with leukemias who were in complete remission for more than five years were more likely to have higher vitamin D levels. However, scientists have simply not done enough studies to know if vitamin D ever cures cancer.