Houghton SC, et al. - Researchers performed a nested case-control study within the prospective Nurses’ Health Study to examine the correlations of plasma folate, B12, pyridoxal 5′-phosphate (PLP), homocysteine, cysteine and cysteinylglycine with breast cancer risk, both before and after fortification. In 1989-1990 (pre-fortification), 32,826 women donated a sample of blood and in 2000-2001 (post-fortification), 18,743 donated an additional blood sample. Between the first blood collection and 2006, 1,874 incident breast cancer cases with at least one blood sample and 367 with two were 1:1 matched to controls. Findings revealed no significant association of plasma folate, B12, PLP, homocysteine, cysteine, and cysteinylglycine with breast cancer overall, before and after fortification, or with specific tumor molecular subtypes.