Vitamin defense

Mice fed a diet deficient in vitamin D and then injected with breast cancer cells developed tumors an average of seven days sooner than mice on a normal diet, and their tumors were significantly larger after six weeks than in the animals with adequate vitamin D, according to a study in March in Endocrinology.

The study linked vitamin D levels with the expression of the ID1 gene, known to accelerate breast-cancer metastasis: Low vitamin D correlated with higher expression of the ID1 gene.

People at risk for the disease should address vitamin D deficiencies but they shouldn’t go overboard on supplements, says the study’s leader, Brian Feldman, MD, PhD, assistant professor of pediatrics. That’s because excess vitamin D has been linked to kidney and cardiovascular damage, he says.