We further investigated the association of vitamin B with the risk of triple-negative cancers (ER-/PR-/HER2-, only 37 cases), but found no significant association between dietary intake of vitamin B and the risk of this poor prognosis breast cancer subtype (HR of 0.51; 95% CI 0.24–1.07 for thiamine, HR of 1.21; 95% CI 0.75–1.94 for riboflavin, HR of 0.69; 95% CI 0.40–1.21 for niacin, HR of 0.59; 95% CI 0.33–1.04 for vitamin B6 and HR of 1.05; 95% CI 0.67–1.65 for folate intake). Here, PGR is linked to breast cancer.