Table 5.
Supplemental Vitamin C Intake | P for trend |
||||
---|---|---|---|---|---|
No use | <500 mg/d | 500–999 mg/d | ≥1,000 mg/d | ||
NHS I and II | |||||
Median supp. vitamin C intake (mg/d) | |||||
NHS I | 0 | 90 | 560 | 1,060 | |
NHS II | 0 | 60 | 545 | 1,060 | |
Cases | 1,856 | 1,891 | 363 | 282 | |
Person-time (y) | 988,407 | 1,086,075 | 228,542 | 191,764 | |
Age-adjusted HR (95% CI) | 1.00 (reference) | 0.90 (0.84–0.96) | 0.88 (0.79–0.99) | 0.79 (0.70–0.89) | 0.002 |
Multivariable HR (95% CI) | 1.00 (reference) | 0.98 (0.90–1.06) | 1.01 (0.90–1.15) | 0.90 (0.79–1.04) | 0.5 |
HPFS | |||||
Median supp. vitamin C intake (mg/d) | 0 | 125 | 560 | 1,120 | |
Cases | 645 | 737 | 203 | 268 | |
Person-time (years) | 189,156 | 271,029 | 74,713 | 80,129 | |
Age-adjusted HR (95% CI) | 1.00 (reference) | 0.83 (0.74–0.93) | 0.82 (0.70–0.99) | 0.98 (0.84–1.13) | 0.3 |
Multivariable HR (95% CI) | 1.00 (reference) | 0.90 (0.80–1.02) | 0.98 (0.82–1.16) | 1.19 (1.01–1.40) | 0.001 |
Note: Multivariable analysis adjusted for age; body mass index; thiazide use; supplemental calcium intake; intake of dietary vitamin C, calcium, sodium, potassium, magnesium, fructose, oxalate, phytate, animal protein, and total fluid; and alcohol intake. For illustrative purposes, medians for supplemental vitamin C were derived from responses to the 1986 (NHS I, HPFS) and 1991 (NHS II) dietary questionnaires. However, supplemental vitamin C intake was updated throughout the study. CI, confidence interval; HPFS, Health Professionals Follow-up Study; HR, hazard ratio; NHS, Nurses’ Health Study; supp, supplemental