TABLE 1.
Age and age-standardized characteristics of participants according to their supplemental vitamin C intake at baseline in the NHS (1980; n = 88,041) and NHSII (1991; n = 93,372)1
| NHS | NHSII | |||||||
|---|---|---|---|---|---|---|---|---|
| Characteristics | Nonusers | Quintile 1 | Quintile 3 | Quintile 5 | Nonusers | Quintile 1 | Quintile 3 | Quintile 5 |
| n | 53,473 | 4668 | 6482 | 7077 | 51,125 | 8455 | 8420 | 8621 |
| Age, years | 46.0 ± 7.1 | 44.9 ± 7.1 | 46.9 ± 7.3 | 47.2 ± 7.1 | 36.8 ± 4.6 | 36.0 ± 4.6 | 35.2 ± 4.6 | 37.6 ± 4.5 |
| Dietary factors and physical activity | ||||||||
| Dietary vitamin C intake, mg/d | 124 ± 70 | 127 ± 67 | 133 ± 71 | 136 ± 73 | 121 ± 68 | 130 ± 68 | 141 ± 75 | 143 ± 80 |
| Supplemental vitamin C intake in users, mg/d | NA | 36 ± 12 | 201 ± 60 | 1303 ± 1083 | NA | 36 ± 10 | 107 ± 21 | 845 ± 368 |
| Use of single vitamin C supplements, % | NA | 6.9 | 54.9 | 86.4 | NA | 7.1 | 42.4 | 93.5 |
| Use of multivitamins, % | 1.9 | 96.0 | 73.6 | 78.1 | 8.4 | 94.5 | 74.8 | 81.3 |
| Total energy intake without alcohol, kcal/d | 1555 ± 499 | 1609 ± 496 | 1593 ± 506 | 1568 ± 506 | 1758 ± 541 | 1826 ± 551 | 1875 ± 554 | 1794 ± 561 |
| Alcohol intake, g/d | 6.2 ± 10.4 | 6.8 ± 10.7 | 6.5 ± 10.8 | 6.8 ± 11.0 | 3.1 ± 6.0 | 3.2 ± 6.2 | 2.7 ± 5.3 | 3.7 ± 6.7 |
| AHEI score (in 1984 for NHS) | 41.7 ± 9.8 | 42.5 ± 10.1 | 44.0 ± 10.3 | 46.8 ± 11.4 | 42.9 ± 10.2 | 43.8 ± 10.1 | 44.3 ± 10.3 | 47.8 ± 11.1 |
| Physical activity level (in 1986 for NHS), MET-h/wk | 12.0 + 17.0 | 13.4 + 17.7 | 13.7 + 19.7 | 14.3 + 22.7 | 19.3 ± 25.3 | 20.7 ± 27.2 | 20.8 ± 27.2 | 26.9 ± 34.0 |
| Reproductive factors | ||||||||
| Menopausal status, % | ||||||||
| Premenopausal | 60.9 | 60.3 | 58.8 | 58.0 | 92.1 | 93.4 | 92.8 | 92.2 |
| Postmenopausal | 32.9 | 33.7 | 35.1 | 34.8 | 7.7 | 6.4 | 6.8 | 7.6 |
| Unknown | 6.2 | 6.0 | 6.2 | 7.2 | 0.2 | 0.2 | 0.5 | 0.2 |
| Age at menopause, y | 47.0 ± 5.8 | 47.5 ± 6.3 | 47.2 ± 5.5 | 46.7 ± 5.9 | 38.9 ± 4.3 | 39.5 ± 4.1 | 38.6 ± 5.1 | 38.5 ± 4.2 |
| Postmenopausal hormone therapy use, % | ||||||||
| Never | 82.6 | 80.5 | 78.4 | 75.5 | 96.1 | 96.7 | 96.4 | 95.5 |
| Current | 7.0 | 8.7 | 10.6 | 11.5 | 3.0 | 2.5 | 2.8 | 3.7 |
| Past | 10.4 | 10.8 | 11.0 | 13.1 | 0.9 | 0.8 | 0.8 | 0.8 |
| Age at menarche <12 years, % | 23.1 | 22.4 | 23.0 | 23.7 | 24.9 | 23.1 | 23.7 | 23.8 |
| Parity, % | ||||||||
| Nulliparous | 5.6 | 4.6 | 6.5 | 7.4 | 24.4 | 23.2 | 21.0 | 39.5 |
| 1 child | 7.0 | 6.7 | 7.4 | 8.5 | 16.3 | 17.2 | 18.9 | 16.9 |
| 2 + children | 87.4 | 88.7 | 86.1 | 84.0 | 59.3 | 59.5 | 60.0 | 43.7 |
| Age at first birth, years | 25.1 ± 3.3 | 25.2 ± 3.2 | 25.2 ± 3.4 | 25.1 ± 3.4 | 25.5 ± 4.0 | 26.0 ± 4.1 | 26.7 ± 4.5 | 26.0 ± 4.3 |
| Duration of breastfeeding, months | 3.2 ± 2.5 | 3.4 ± 2.5 | 3.4 ± 2.6 | 3.4 ± 2.6 | 0.3 ± 0.4 | 0.3 ± 0.5 | 0.3 ± 0.5 | 0.3 ± 0.4 |
| Ever use of oral contraceptive, % | 48.3 | 48.9 | 50.2 | 50.8 | 88.1 | 89.3 | 93.5 | 88.7 |
| Medical factors | ||||||||
| Personal history of benign breast disease, % | 23.2 | 25.3 | 27.4 | 27.8 | 9.5 | 9.5 | 9.1 | 9.9 |
| Family history of breast cancer, % | 6.1 | 6.1 | 6.1 | 6.6 | 5.8 | 5.9 | 6.2 | 6.5 |
| Anthropometric factors | ||||||||
| Height, cm | 164 ± 8.2 | 164 ± 7.6 | 164 ± 9.2 | 164 ± 8.2 | 165 ± 6.6 | 165 ± 6.5 | 165 ± 6.7 | 165 ± 6.7 |
| BMI, kg/m2 | 24.6 ± 4.6 | 24.0 ± 4.1 | 24.0 ± 4.1 | 24.1 ± 4.5 | 24.8 ± 5.4 | 24.2 ± 4.8 | 24.8 ± 5.0 | 23.9 ± 4.9 |
| BMI at age 18, kg/m2 | 21.4 ± 3.0 | 21.1 ± 2.8 | 21.2 ± 2.9 | 21.4 ± 3.1 | 21.3 ± 3.4 | 21.1 ± 3.0 | 21.2 ± 3.2 | 21.2 ± 3.3 |
| Weight change since age 18, kg | 6.7 ± 9.9 | 6.1 ± 8.9 | 6.1 ± 9.3 | 5.9 ± 9.6 | 9.6 ± 11.7 | 8.8 ± 10.5 | 10.0 ± 11.0 | 7.6 ± 11.2 |
1
Vitamin C intake was adjusted for total energy intake using the residual method. Data are shown as percentage or mean ± SD. Abbreviations: AHEI, alternate healthy eating index; MET, metabolic equivalent of task; NA, not applicable; NHS, Nurses’ Health Study; NHSII, Nurses’ Health Study II.