Table 2.
Multiple linear regression results1 for serum vitamin C concentrations in the US population 20 years and older, National Health and Nutrition Examination Survey, 2017–2018
| Variables2 | Variable Categories | Reference Category | Beta coefficient (95% CI) | p-value3 |
|---|---|---|---|---|
| Age (years) | Intercept4 | ≥60 | 50.4 (45.2, 55.7) | <0.0001 |
| 20–39 | −3.1 (−6.6, 0.4) | 0.07 | ||
| 40–59 | −5.3 (−8.3, −2.3) | 0.0019 | ||
| Sex | Men | Women | −5.7 (−8.9, −2.5) | 0.0017 |
| Race/Hispanic Origin | Mexican American | Non-Hispanic White | −0.8 (−3.3, 1.8) | 0.52 |
| Non-Hispanic Asian | −1.6 (−4.6, 1.4) | 0.28 | ||
| Non-Hispanic Black | −0.4 (−4.1, 3.3) | 0.82 | ||
| Poverty Income Ratio | Low (0 – 1.85) | High (>3.5) | −1.4 (−4.2, 1.4) | 0.30 |
| Middle (1.86 – 3.5) | 0.2 (−4.0, 4.4) | 0.91 | ||
| Body Mass Index (kg/m2) | Healthy (18.5 – 24.99) | Obesity (≥30) | 8.3 (4.6, 12.0) | 0.0002 |
| Overweight (25 – 29.99) | 9.3 (6.6, 12.0) | <0.0001 | ||
| Dietary Intake Quartiles (mg/day) | (0 – <20) | ≥110 | −17.5 (−21.2, −13.9) | <0.0001 |
| (20 – <50) | −14.7 (−18.4, −11.0) | <0.0001 | ||
| (50 – <110) | −7.5 (−10.5, −4.5) | 0.0001 | ||
| Vitamin C-containing Supplement Use | Yes | No | 19.2 (16.7, 21.6) | <0.0001 |
| Smoking Status | Non-smokers | Smokers | 8.6 (5.9, 11.3) | <0.0001 |
1
R2 = 29.4%
2
Data were adjusted for the following variables: age, sex, race/Hispanic origin, poverty income ratio, body mass index, dietary intake quartiles, vitamin C-containing supplement use, and smoking status.
3
Student’s t-statistic with 15 degrees of freedom
4
The regression intercept is the average vitamin C level when all model covariates are set to the reference level.