Table 4.

Joint Association of Folate and Dietary Factors With Risk of Premenopausal Breast Cancer for 32,377 Women Who Do Not Use B Vitamin Supplements, Shanghai Women's Health Study, 1997–2008

	Daily Mean Intake	Tertile of Daily Folate Intakea
		1 (Low)		2		3		P for Trend
		HR	95% CI	HR	95% CI	HR	95% CI
Mean intake, μg/day		211		283		377
Methionine, g
Low	1.28	1.0	Ref	0.74	0.44, 1.26	1.09	0.61, 1.96	0.88
High	1.75	1.47	0.88, 2.45	1.08	0.65, 1.81	1.10	0.64, 1.89	0.37
P for interaction		0.11
Vitamin B12, μg
Low	1.59	1.0	Ref	0.81	0.47, 1.39	0.87	0.47, 1.59	0.64
High	3.60	1.19	0.72, 1.95	0.86	0.52, 1.42	1.05	0.62, 1.79	0.63
P for interaction		0.30
Vitamin B6, mg
Low	1.42	1.0	Ref	0.72	0.44, 1.16	1.03	0.56, 1.92	0.63
High	1.99	0.85	0.47, 1.56	0.74	0.46, 1.21	0.80	0.48, 1.34	0.97
P for interaction		0.58
Niacin (vitamin B3), mg
Low	12.6	1.0	Ref	1.10	0.67, 1.81	1.02	0.55, 1.89	0.77
High	15.9	1.57	0.96, 2.57	0.85	0.49, 1.45	1.18	0.67, 2.06	0.30
P for interaction		0.31
Riboflavin (vitamin B2), mg
Low	0.67	1.0	Ref	0.64	0.39, 1.05	0.88	0.48, 1.61	0.36
High	1.03	0.74	0.41, 1.35	0.78	0.48, 1.26	0.82	0.49, 1.36	0.95
P for interaction		0.99

Abbreviations: CI, confidence interval; HR, hazard ratio; Ref, reference.

^aAdjusted for age at baseline (years), age at menarche (years), parity (ever, never), age at first livebirth (years), educational attainment (college or above, high school, middle school, less than middle school), physical activity (metabolic equivalent-hours/week per year), use of a B vitamin supplement (never, ever), height (m), and total daily intakes of energy (kcal), vegetables (g), and fat (g).