Table 3.
Effect of vitamin C intake on disease risk/mortality in major observational studies. Major limitations of the presented studies are that i) they estimate vitamin C intake as surrogate for vitamin C status, ii) most studies suffer from selection bias and iii) only a single estimate of vitamin C intake is used.
| Survey Data | The Nurses' Health Study [73] | Etude Epidémiologique aupre's de femmes de la Mutuelle Générale de l’Education Nationale [78] |
The Health Professionals Follow-up Study [79] |
EPICOR Study [80] | Iowa Women's Health Study [81] |
|---|---|---|---|---|---|
| Study Population | 85,118 healthy US female nurses, aged 30–45 yrs | 57,403 French healthy women, aged 40–65 yrs | 43,738 US men w/o CVD or diabetes, aged 40–75 yrs | 41,620 Italian men & women w/o MI or stroke, aged 44–61 yrs | 34,492 US postmenopausal women, aged 55–69 yrs |
| Highest median vitC intake (mg/d) | 704; top quintile | 228a; top quartile | 1167; top quintile | 201; top tertile | 679; top quintile |
| Lowest median vitC intake (mg/d) | 70; bottom quintile | 77.5a; bottom quartile | 95; bottom quintile | 83; bottom tertile | 82; bottom quintile |
| Adjustments | Age, energy intake, supplements use, alcohol, smoking status, and diabetes | Age, oral contraceptives, hormone therapy, alcohol, BMI, physical activity, energy intake, smoking, supplement use, education, and specific breast cancer risk factors | Age, season, smoking, energy intake, alcohol, hypertension, parental history of MI, profession, BMI and physical activity. | Age, center, sex, hypertension, smoking, education, energy intake, alcohol, waist circumference, obesity, and physical activity. | Age, BMI, waist-to-hip ratio, hypertension, diabetes, ERT, education, marital status, smoking, physical activity, energy intake, cholesterol, alcohol, saturated fat, fish, vitE, carotenoids, fiber, and whole grains |
| Follow-up period (years) | 16 | 10 | 8 | 7.9 | 11 |
| Endpoint | CHD | Postmenopausal breast cancer | Stroke | Stroke | Death from stroke |
| Outcome | Inverse association between vitC intake and risk of CHD. VitC supplementation was associated with lower risk of CHD | VitC supplement use not associated with breast cancer risk; Top quartile of vitC intake from foods only showed increased risk of breast cancer | Neither vitC intake nor supplementation was associated with lower risk of stroke | VitC associated with lower risk of ischemic stroke | No association between vitC intake and death from stroke |
Abbreviations: BMI, body mass index; CHD, chronic heart disease; CVD, cardiovascular disease; DBP, diastolic blood pressure; ERT, estrogen replacement therapy; IHD Ischemic heart disease; MI, myocardial infaction; SBP, systolic blood pressure; vitC, vitamin C; vitE, Vitamin E. aReported as mean intake from food only.