While a number of studies have linked vitamin D levels to a reduction in the risk of certain cancers, including breast cancer, there has been much debate as to how to boost vitamin D levels, namely – by exposure to sunlight or via dietary supplementation.  Pierre Engel, from INSERM (Institut National de la Santé et de la Recherche Médicale; France), and colleagues analyzed data collected over a decade of study from 67,721 women. The team found that postmenopausal women living in sunny climates, combined with high dietary or supplemental intakes of vitamin D, were at a significantly reduced risk of breast cancer.  Concluding that: “Our results suggest that a threshold of vitamin D exposure from both sun and diet is required to prevent [breast cancer] and this threshold is particularly difficult to reach in postmenopausal women at northern latitudes where quality of sunlight is too poor for adequate vitamin D production,” the researchers urge that: “Prospective studies should further investigate associations between [breast cancer] risk, vitamin D status and sunlight exposure.”