Table 1.
Baseline‡ characteristics of the study population according to quintile of dietary fiber intake
| Quintile 1 (n = 34,229) |
Quintile 2 (n=33,815) |
Quintile 3 (n=34,097) |
Quintile 4 (n=34,360) |
Quintile 5 (n=33,810) |
|
|---|---|---|---|---|---|
|
Median total fiber intake (IQR) (g/day) |
11.6 (10.3 – 12.6) | 14.5 (13.7 – 15.4) | 16.8 (15.8 – 17.6) | 19.4 (18.5 – 20.3) | 24.0 (22.4 – 26.8) |
|
Mean age (in years) (standard deviation) |
41.9(8.8) | 42.3(8.9) | 43.0(9.1) | 43.4(9.4) | 44.4(9.7) |
| White race (%) | 96 | 97 | 97 | 97 | 97 |
| Smoking status (%) | |||||
| Never Smoker | 49 | 55 | 56 | 58 | 59 |
| Past Smoker | 23 | 25 | 27 | 28 | 30 |
| Current Smoker | 28 | 20 | 16 | 13 | 11 |
|
Ever oral contraceptive use (%) |
69 | 69 | 69 | 68 | 68 |
| Post-menopausal (%) | 31 | 31 | 30 | 31 | 32 |
| Post-menopausal | |||||
| hormone use (%)† | |||||
| Never Users | 57 | 55 | 55 | 52 | 52 |
| Past Users | 20 | 21 | 21 | 21 | 19 |
| Current Users | 23 | 24 | 24 | 28 | 29 |
| Body Mass Index (%) | |||||
| < 20.0 kg/m2 | 16 | 14 | 14 | 13 | 15 |
| 20.0 – 24.9 kg/m2 | 50 | 51 | 52 | 53 | 54 |
| 25.0 – 29.9 kg/m2 | 21 | 22 | 22 | 22 | 21 |
| ≥ 30.0 kg/m2 | 13 | 13 | 12 | 11 | 10 |
|
Regular aspirin use± (%) |
19 | 19 | 19 | 17 | 15 |
|
Regular NSAID use± (%) |
11 | 11 | 11 | 12 | 12 |
|
Mean fiber intake from various sources (g/day) (SD) |
|||||
| Fruits | 1.7(1.0) | 2.5(1.3) | 3.2(1.6) | 4.1(1.9) | 5.8(3.1) |
| Vegetables | 4.0(1.4) | 5.3(1.5) | 6.2(1.8) | 7.3(2.2) | 10.0(4.1) |
| Cruciferous vegetables |
0.6(0.4) | 0.8(0.5) | 0.9(0.6) | 1.1(0.7) | 1.6(1.3) |
| Whole grains | 8.4(7.2) | 12.6(9.2) | 16.0(10.9) | 20.7(13.3) | 30.3(20.5) |
| Cereals | 3.3(1.3) | 4.1(1.6) | 4.7(1.9) | 5.5(2.3) | 7.2(4.4) |
| Bran | 1.8(2.2) | 2.9(3.0) | 3.9(3.8) | 5.5(5.1) | 9.2(9.5) |
| Legumes | 0.5(0.6) | 0.7(0.7) | 0.8(0.8) | 1.0(0.9) | 1.5(1.6) |
|
Mean total fat intake (g/day) (SD) |
66.6 (12.2) | 65.7 (9.9) | 63.6 (9.2) | 60.8 (9.0) | 55.0 (9.8) |
|
Mean carbohydrate intake (g/day)(SD) |
191 (44) | 197 (35) | 203 (32) | 212 (32) | 231 (36) |
|
Mean total protein intake (g/day) (SD) |
76.5(17.6) | 78.8(15.8) | 80.1(15.4) | 81.7(15.4) | 81.9(16.3) |
SD – standard deviation; NSAID – non-steroidal anti-inflammatory drugs; g/day – grams per day; IQR – interquartile range
‡
Baseline characteristics according to the 1984 questionnaire for Nurses Health Study I and 1991 questionnaire for Nurses Health Study II.
Dietary fiber categories according to energy-adjusted intake.
†
Percentages among postmenopausal women
±
regular use was defined as intake of 5 or more times per month
The United States Department of Agriculture and National Academy of Sciences recommend an intake of at least 21 grams/day of fiber for women and 30 grams/day for men.