Vitamin D may help curb breast cancer progression, suggests a small study published ahead of print in the Journal of Clinical Pathology.

The authors reach their conclusion from a study of 279 women with invasive breast cancer. The disease was in the early stages in 204 women, and advanced in the remainder.

Serum levels of vitamin D, parathyroid hormone, and calcium were measured in both groups of women.

The results showed that women with early stage disease had significantly higher levels of vitamin D and significantly lower levels of parathyroid hormone than did the women with advanced disease.

There was little difference in calcium levels between the two groups.

The authors say that the exact reasons for the disparity are unclear, nor is it known whether the low levels of vitamin D among those with advanced disease are a cause or consequence of the cancer itself.

But it is known that vitamin D treatment boosts the activity of certain key genes and dampens it down in others. One gene that is boosted is p21, which has an important role in controlling the cell cycle.

Low levels of vitamin D may therefore promote progression to advanced disease, venture the authors.

Laboratory studies have also shown that vitamin D stops cancer cells from dividing and that it enhances cell death. And the epidemiological evidence points to a link between rates of, and deaths from, breast cancer and exposure to sunlight.

Source: British Medical Journal