Vitamin D - manufactured by the skin in response to sunlight - may have a role to play in fighting breast cancer, scientists say today. Researchers from Imperial College, London, have carried out a small but significant study showing that vitamin D levels in the blood of women with early breast cancer are higher than in those with advanced disease. It is possible, they say, that vitamin D actively helps to curb the progression of the disease.

There is already some evidence that vitamin D - and sunlight - have a beneficial effect with regard to breast cancer. Countries that are further north and enjoy fewer hours of sunshine have a higher incidence of breast cancer and women living in them are at greater risk of dying from the disease than those in the sunnier southern climes.

Vitamin D is also found in eggs and fatty fish. It has also been shown that the vitamin can stop cancer cells dividing in laboratory experiments, which they must do for tumours to grow. Other research has shown that women with adequate levels of vitamin D in their blood have a reduced risk of getting the disease.

It is known that vitamin D can boost the activity of certain genes and dampen down others. One gene that is boosted is p21, which has an important role in controlling the cell cycle.

The latest study, published in the Journal of Clinical Pathology - the first to compare vitamin D levels in the blood of women with early and late stage cancer - may help inspire new treatments for breast cancer, the researchers say, possibly by raising vitamin D levels.

"This report, while being an observational study, clearly shows that circulating vitamin D levels are lower in advanced breast cancer as compared to early breast cancer," said the lead researcher, Carlo Palmieri, from the department of cancer medicine at Imperial college. "It lends support to the idea that vitamin D has a role in the progression of breast cancer.

"The next step in this research is to try and understand the potential causes and mechanisms underlying these differences and the precise consequences at a molecular level. We also need to look at the potential clinical implications of monitoring and maintaining high circulating vitamin D levels in breast cancer patients."

The study was small - involving blood tests from 279 women, 204 of whom had early-stage breast cancer while the rest had advanced disease. The researchers point out that it is also possible that the cancer itself is responsible for lowering the levels of vitamin D. Further studies are needed.