Table 4.

Prospective Studies of Folate and Breast Cancer.

Reference	Study	# Cases	# Controls	Outcomes	Comment
[214]	Nurses' Health Study	3,483		↓folate intake + alcohol = ↑risk of breast cancer (OR = 0.55, P-trend = 0.001)	Folate intake not associated with overall risk of breast cancer
[215]	Canadian National Breast Screening Study	1,336	5,382	↓folate intake + alcohol = ↑risk of breast cancer (OR = 0.34, P-trend = 0.004)	Folate intake not associated with overall risk of breast cancer
[216]	Prospective study in USA with postmenopausal women	1,586		Among drinkers, ↓folate intake = ↑breast cancer risk (OR = 1.59)	No association in overall cohort
[125]	Shanghai Breast Cancer Study, China	1,321	1,382	↑folate intake = ↓ risk (OR = 0.71, P-trend = 0.05); ↑folate, ↑methionine, ↑B6, ↑B12 = ↓risk (OR = 0.47, P-trend = 0.01)	No alcohol, no supplements, unprocessed, unfortified foods
[217]	Nurses' Health Study II, study of premenopausal women	714		Vitamin A protective (OR = 0.28); Vitamins C, E, and folate not associated with risk.
[118]	Nurses' Health Study	712	712 matched	↑plasma folate = ↓risk (OR = 0.73, P-trend = 0.06). For women who drank alcohol, ↑plasma folate even more protective, OR = 0.11.	↑plasma B6 and plasma B12 were also protective
[218]	Prospective study in USA with postmenopausal women	1,823, 308 with family history (FH)		FH- +Alcohol = ↑risk (OR = 1.40) FH- + Alcohol + ↑folate = normal risk; FH+ ↓folate = ↑risk for drinkers (OR = 2.21) and non-drinkers (OR = 2.39); FH+ +Alcohol + ↑folate = ↑risk (OR = 1.67); FH+ + ↑folate = normal risk	Women with family history of breast cancer can reduce risk by increasing folate intake and not drinking.

FH = Family History