By David Liu, PHD

Saturday Dec 15, 2012 (foodconsumer.org) -- Once again a study suggests that taking vitamin D supplements or getting sufficient exposure to the sun to maintain certain levels of serum vitamin D may help prevent breast cancer.

K. Bilinski and J. Boyages from Westmead Breast Cancer Institute, Westmead Hospital in Australia published in the study Breast Cancer Research and Treatment that reveals the association between vitamin D insufficiency was associated with increased risk of breast cancer.

The researchers compared 214 women newly diagnosed with breast cancer with 852 controls without the disease for their serum levels of 25-hydroxyvitamin D (25(OH)D), measured between Aug 2008 and July 2010.  In the study, a serum level of 75nmol/L or higher was defined as sufficient, 50 to 74 nmol/L as insufficient and 25 to 49 nmol/L as deficient.

The objective of this study is to examine the association between vitamin D status and risk of breast cancer in an Australian population of women. The study design is observational case-control study, performed at Westmead Breast Cancer Institute, Westmead Hospital, Sydney, Australia. 

214 women newly diagnosed with breast cancer were matched to 852 controls, and their blood samples were tested at the same laboratory between August 2008 and July 2010. 

Overall, breast cancer patients had significantly lower serum vitamin D, compared with controls, 53.0 versus 62.0 nmol/L.  And serum vitamin D was inversely associated with risk of breast cancer.

Those whose vitamin D was severely deficient, deficient, or insufficient, compared with sufficient vitamin D concentration, were 2.3, 2.5 and 2.5 fold more likely to be diagnosed with breast cancer, respectively.

The study shows that "a 25(OH)D concentration below 75 nmol/L at diagnosis was associated with a significantly higher risk of breast cancer."

Some researchers suggest that sufficient vitamin D levels can prevent 75% of all breast cancer cases.  The question, how much vitamin D does a woman need to have the preventive effect?