The authors of a new study are suggesting that vitamin D may slow down the progression of breast cancer.
The researchers from Imperial College London have reached this conclusion after studying 279 women with invasive breast cancer.
In 204 of the women the disease was in the early stages and advanced in the remainder.
Serum levels of vitamin D, parathyroid hormone, and calcium were measured in both groups of women and they found that the patients with the early breast cancer had significantly higher levels of the vitamin D and significantly lower levels of parathyroid hormone, than those with more advanced disease.
There was apparently little difference in calcium levels between the two groups.
Dr. Carlo Palmieri says it is unclear whether the low levels of vitamin D are a cause or a consequence of the cancer, but they know from previous studies that breast cancer incidence is higher in women who live in higher latitudes and have less sun exposure.
Vitamin D treatment is thought to boost the activity of certain key genes and dampens it down in others; one of the genes that is boosted is p21, which controls the cell cycle.
The authors suggest that low levels of vitamin D may therefore promote the progression to advanced disease.
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.
Breast cancer is the most common cancer in women, with more than a million cases detected worldwide each year.
According to the International Agency for Research on Cancer (IARC) in Lyon, France breast cancer is the most common cancer in women, with more than a million cases detected worldwide each year.
The earlier the cancer is detected and treated, the greater the chances of survival.
Breast cancer is treated with surgery and radiotherapy, chemotherapy and hormone treatment, or a combination of them, depending on the cancer and stage of the illness.
Factors which can increase a woman's risk of breast cancer include having a mother or close relative with the disease, inherited mutations in the BRCA1 or BRCA2 genes, an early puberty, late menopause and not having any children.
The research is published in the Journal of Clinical Pathology.