Folic acid supplement use and breast cancer risk in BRCA1 and BRCA2 mutation carriers: a case-control study.

In this first investigation of folic acid supplement use and breast cancer risk in BRCA mutation carriers, these findings suggest that moderate folic acid- and vitamin B12-containing supplement use may be protective for BRCA-associated breast cancer, particularly among BRCA1 mutation carriers. Future studies with larger samples and prospective follow-up are needed.