Table 4.
Effect of vitamin C status on disease risk/mortality in major observational studies. Limitations of the presented studies are that they i) used non-fasted blood samples, ii) less than optimal analytical methodology and iii) do not account for possible multi-deficiencies.
| Survey Data | EPIC-Norfolk [83] | EPIC-Norfolk [84] | NHANES II [85] | NHANES II [87] | NHANES II [86] |
|---|---|---|---|---|---|
| Study Population | 20,649 men and women from Norfolk, UK, aged 40–79 yrs | 19,496 men and women from Norfolk, UK, aged 45–79 yrs | 8417 US men and women, aged 30–75 yrs | 7071 US men and women aged 30–75 yrs | 6624 US men and women aged 40–74 yrs |
| Highest group vitC conc (μmol/L) | ≥66.0; top quartile | 79.2; top quintile | 79.5 (64.7–158.8) | ≥73.8; top quartile | 85.2 (64.7–158.8) |
| Lowest group vitC conc (μmol/L) | <41.0; bottom quartile | 25.9; bottom quintile | 17.0 (5.7–22.7) | <28.4; bottom quartile | 17.0 (5.7–22.7) |
| Fasted blood samples (Yes/No) | No | No | No | No | No |
| Method of analysis | Fluorometric assay | Fluorometric assay | Colorimetric assay | Colorimetric assay | Colorimetric assay |
| Adjustments | Age, sex, smoking, BMI, SBP, cholesterol, physical activity, diabetes, MI, social class, alcohol & supplement use | Age, systolic blood pressure, cholesterol, smoking, diabetes, & supplement use | Gender | Smoking status | Age, sex, race, education, physical activity, smoking, alcohol, cholesterol, BMI, diabetes, hypertension, aspirin and vitE use |
| Follow-up period (years) | 9.5 | 4 | ?* | 12–16 | ?* |
| Endpoint | Stroke | All-cause, CVD, IHD and cancer mortality | All-cause, CVD and cancer mortality | Cancer & all-cause mortality | CVD |
| Outcome | Risk of stroke was 42% lower in top vs bottom quartile | VitC inversely related to all-cause, CVD & IHD death. Risk of death was about half in top vs bottom quintile | Mid and top vitC groups had 25–29% decreased risk of all-cause mortality compared to bottom vitC group | Men in bottom vs top quartile had 57% increased risk of all-cause mortality & 62% higher risk of cancer death | Serum vitC independently associated with CHD & stroke; 27% lower risk in top vs bottom group |
Abbreviations: BMI, body mass index; CHD, chronic heart disease; CVD, cardiovascular disease; IHD, Ischemic heart disease; MI, myocardial infaction; SBP, systolic blood pressure; vitC, vitamin C; vitE, Vitamin E. *Follow-up period not specifically specified.