Table 4.
Dietary and water nitrate intakes (quintiles) in relation to breast cancer risk stratified by total folate intake
| Total folate intake
|
||||
|---|---|---|---|---|
| <400 μ/d
|
≥400 μg/d
|
|||
| Cases | HR (95%CI)a | Cases | HR (95%CI)a | |
|
|
|
|||
| Dietary nitrate (mg/d) | ||||
| Q1 (≤65.2) | 456 | 1.0 (reference) | 148 | 1.0 (reference) |
| Q2 (65.2 – 91.8) | 374 | 0.81 (0.69 – 0.94) | 167 | 1.00 (0.79 – 1.28) |
| Q3 (91.8 – 121.8) | 398 | 0.93 (0.79 – 1.09) | 177 | 0.82 (0.64 – 1.05) |
| Q4 (121.8 – 165.6) | 311 | 0.83 (0.70 – 1.00) | 290 | 1.18 (0.93 – 1.49) |
| Q5 (≥165.6) | 192 | 0.83 (0.67 – 1.02) | 362 | 0.94 (0.73 – 1.22) |
| ptrend | 0.19 | 0.87 | ||
| Water nitrate (mg/2L)b | ||||
| Q1 (≤2.8) | 169 | 1.0 (reference) | 84 | 1.0 (reference) |
| Q2 (3.0 – 7.9) | 151 | 0.97 (0.77 – 1.22) | 104 | 1.25 (0.92 – 1.68) |
| Q3 (8.0 – 14.1) | 140 | 0.88 (0.70 – 1.12) | 104 | 1.12 (0.83 – 1.52) |
| Q4 (14.3 – 33.3) | 150 | 0.92 (0.73 – 1.16) | 100 | 1.31 (0.97 – 1.78) |
| Q5 (≥33.5) | 168 | 1.00 (0.79 – 1.25) | 118 | 1.40 (1.05 – 1.87) |
| ptrend | 0.71 | 0.04 | ||
| Private well users | 283 | 1.01 (0.83 – 1.24) | 180 | 1.38 (1.05 – 1.82) |
Adjusted for age (continuous), total energy intake (continuous), BMI (continuous), WHR (continuous), education (<high school, high school, >high school), smoking (never, previous, current), physical activity level (low, moderate, high), alcohol intake (yes, no), family history of breast cancer (yes/no), age at menopause (continuous), age at first live birth (<20, 20 – <30, ≥30, nulliparous), and estrogen use (never, ever), and total intake of vitamin C and E and flavonoids, intakes of cruciferae and red meat.
Analysis includes 20,147 women (15,151 public water supply users and 4,996 private well users) who responded to the 1989 follow-up survey, had used public water private well water supply for more than 10 years, and lived in communities which were served by one water source and had nitrate measurement data.