Breast cancer is the most common cancer in women, and its frequency is rising in countries with low and middle incomes. The influence of diet on mammary carcinogenesis has been clearly demonstrated in animal models. Inadequate folate intake has been associated with several cancers, and low levels of serum folate, vitamin B6, and vitamin B12 have been associated with increased breast cancer risk. The levels of folic acid, B6, and B12 in the plasma of 85 people with breast cancer were measured and compared with healthy people. A significant inverse trend was observed between folate intake (p-value=0.004) and vitamin B6 intake (p-value=0.0001) and breast cancer risk. Data from this study suggests that B vitamins, including folate, vitamin B-6, and vitamin B-12, may confer little or no reduction in overall risk of developing breast cancer.