TL;DR Vitamin D *deficiency* is cancer risk and relatively common. High doses don't work. >When all 14 studies were pooled, no statistically significant result

TL;DR Vitamin D *deficiency* is cancer risk and relatively common. High doses don't work. >When all 14 studies were pooled, no statistically significant results emerged. However, when the studies were divided according to whether vitamin D3 was taken daily in a low dose* or in higher doses administered at longer intervals*, a large difference was seen. In the four studies with the infrequent hogher doses, there was no effect on cancer mortality. In contrast, in the summary of the ten studies with daily dosing, the researchers determined a statistically significant twelve percent reduction in cancer mortality. >"We observed this twelve percent reduction in cancer mortality after untargeted vitamin D3 administration to individuals with and without vitamin D deficiency. We can therefore assume that the effect is significantly higher for those people who are actually vitamin D deficient,"