The results showed that vitamin D levels were significantly higher and parathyroid hormone levels were significantly lower in the women with early stage breast cancer compared with women who had advanced breast cancer. Calcium levels were not significantly different between the two groups.
The authors are unclear why there should be a difference in vitamin D levels between the two groups and cannot say whether lower levels are a cause or consequence of advanced breast cancer.
However, vitamin D is known to reduce the activity of p21, a gene which has an important role in controlling the cell cycle. Laboratory studies have also shown that vitamin D stops cancer cells from dividing and enhances cell death.