Women with low levels of vitamin D are at an increased risk of developing breast cancer, according to a new study.
The study involved 1,394 patients with breast cancer and an equal number of healthy women after menopause.
A connection between vitamin D level and breast cancer risk has been implicated for a long time, but its clinical relevance had not yet been proven.
Researchers Sascha Abbas and colleagues from the working group headed by Dr. Jenny Chang-Claude at the German Cancer Research Centre (Deutsches Krebsforschungszentrum, DKFZ), along with researchers from the University Hospitals in Hamburg-Eppendorf focussed their study on the connection.
They used 25-hydroxyvitamin D (25(OH)D) as a marker for both endogenous vitamin D and vitamin D from food intake.
The findings revealed that women with a very low blood level of 25(OH)D have a greater risk of developing breast cancer.
The effect was found to be strongest in women who were not taking hormones for relief of menopausal symptoms.
For further analysis of the link between vitamin D and breast cancer risk, the team focused on the vitamin D receptor.
The gene of this receptor is found in several variants known as polymorphisms. They examined the effect of four of these polymorphisms on the risk of developing breast cancer.
They found that carriers of the Taql polymorphism have a slightly increased risk of breast tumours that carry receptors for the female sex hormone estrogen on their surface.
The researchers suggest that vitamin D can exert its cancer-preventing effect by counteracting the growth-promoting effect of estrogens.
Besides its cancer-preventing influence with effects on cell growth, cell differentiation and programmed cell death (apoptosis), vitamin D regulates, the calcium metabolism in the body.