Table 1.
Characteristics of study population: National Health and Nutrition Examination Survey (NHANES), 1999–2004 1.
| Characteristic | Men | Women | p-Value 2 |
|---|---|---|---|
| (n = 9020) | (n = 9549) | ||
| Race-ethnicity | |||
| Non-Hispanic white, n, (%) | 3971 (48.9) | 4199 (51.1) | 0.023 |
| Non-Hispanic black, n, (%) | 2140 (45.2) | 2211 (54.8) | <0.0001 |
| Hispanic/Mexican, n, (%) | 2909 (49.7) | 3139 (50.3) | 0.72 |
| Age (year) | |||
| 12–14, n (%) | 1125 (51.1) | 1187 (48.9) | 0.41 |
| 15–17 years, n (%) | 1178 (51.4) | 1056 (48.6) | 0.30 |
| 18–40 years, n (%) | 2775 (49.7) | 3328 (50.3) | 0.63 |
| 41–65 years, n (%) | 2254 (49.1) | 2274 (50.9) | 0.16 |
| >65 years, n (%) | 1590 (42.6) | 1598 (57.4) | <0.0001 |
| Supplements use 3 | |||
| Yes, n (%) | 3222 (42.9) | 4459 (57.1) | <0.0001 |
| No, n (%) | 5798 (54.3) | 5090 (45.7) | <0.0001 |
| Serum creatinine, μmol/L (mean ± SE) | 83.4 ± 0.5 | 64.7 ± 0.4 | <0.001 |
| Serum vitamin B-12, pmol/L (mean ± SE) | 380.8 ± 7.0 | 418.5 ± 17.1 | 0.04 |
1 NHANES 1999–2000, 2001–2002 and 2003–2004, conducted after the folic acid fortification commenced, were combined into one analytic data set, 1999–2004. n = 18,569. Weighted n = 204,316,278. Percentages in parentheses are based on weighted sample size. 2 Significance between men and women. Rao-Scott χ2 test or unpaired t-test. 3 Persons who took vitamin/mineral supplements one month prior to the survey.