For years researchers have been finding links between vitamin D and all sorts of health benefits, including lower incidence of cancer with higher vitamin D levels. A recent study by Michigan State physicians found that taking vitamin D supplements for at least 3 years resulted in cancer patients living longer, that is, "having significant reduction of cancer-related mortality" . However, it did not prevent cancer.
One issue with much of the vitamin D research that has been done is whether vitamin D is really causing these health benefits or is it just an association? Perhaps people who take vitamin D are also different in some way from those who don't, or something else is going on, and this may be confusing the results.What was nice about this study is that it was a review of studies already done, but the researchers only included vitamin D studies that used randomly controlled trials (RCT).
In the RCTs included in the study, people were randomly assigned to different groups and either they were 1) given vitamin D supplements for 3 years or more, or 2) they did not take vitamin D supplements (the placebo group). Thus they evaluated 10 RCT studies with 79,055 persons who were followed for 4 years or more. Vitamin D was associated with significant reduction of cancer-related deaths (when compared with the placebo group). But there was no reduction in cancer incidence. Meaning the vitamin D did not prevent cancer (have a protective effect) in the studies they looked at.
The researchers did not say what they thought was an optimal vitamin D supplement dose or optimal levels in the blood. By the way, keep in mind that vitamin D can easily be gotten from exposure to sunshine. After all, it is called the sunshine vitamin.
From Science Daily: Vitamin D could help cancer patients live longer
Michigan State University physicians have found that vitamin D, if taken for at least three years, could help cancer patients live longer. The findings suggest that the vitamin carries significant benefits other than just contributing to healthy bones and were presented at the American Society of Clinical Oncology annual meeting on June 3, 2019.
"Vitamin D had a significant effect on lowering the risk of death among those with cancer, but unfortunately it didn't show any proof that it could protect against getting cancer," said Tarek Haykal, a lead author on the study and an internal medicine resident physician at Michigan State University and Hurley Medical Center in Flint, Michigan.
The researchers looked at data related to disease prevention from more than 79,000 patients in multiple studies that randomly compared the use of vitamin D to a placebo over at least a three-year period. Haykal and his team zeroed in on any information that involved cancer incidence and mortality. "The difference in the mortality rate between the vitamin D and placebo groups was statistically significant enough that it showed just how important it might be among the cancer population," Haykal said.
While these findings show promise, Haykal cautioned that the exact amount of the vitamin to take and what levels are needed in the blood are still unknown. He also said that it's unclear how much longer vitamin D extends lifespan and why it has this result. "There are still many questions and more research is needed," Haykal said. "All we can say is that at least three years of taking the supplement is required to see any effect."
Results show enough promise, however, that Haykal would like to see more doctors, especially oncologists, prescribe vitamin D to patients in general. "We know it carries benefits with minimal side effects, he said. "There's plenty of potential here."