Commentary: Health policies in the US: can they increase or decrease the gap between subgroups of the population? The case of folic acid.

Effective on January 1, 1998, the Food and Drug Administration (FDA) amended the standards to identify several enriched grain products, bromated flour, vegetable macaroni and vegetable noodle products by requiring folic acid fortication. Specifically, the FDA required that these products be fortified with folic acid levels ranging from 0.43 to 1.4 mg/pound or 95 to 309 mg/100 g of product. Although this requirement affects the entire population, the purpose of this amendment was to ensure that women of childbearing age consume the US Public Health Service recommended daily allowance of at least 0.4 mg (400 mg) of folic acid daily to reduce their risk of having a child with spina bifida or other neural tube defects (NTDs). Spina bifida and anencephaly affect approximately 4000 children in the US prior to the folic acid fortification amendment. However, approximately 1000 of these cases have been prevented with folic acid fortification. As with most conditions in the US, estimates for NTDs vary by race and ethnicity, with Hispanics exhibiting the highest estimates and blacks and Asians the lowest. Moreover, NTDs varies by socioeconomic status defined using income and education with the least educated and those with low income exhibiting the highest estimates. Low folate levels not only affect children in utero, but also evidence suggests that low folate levels are associated with increased prevalence of cancer, cardiovascular disease, physical and mental functioning. Thus, despite the fact that the fortification was targeted to women of childbearing age, the FDA amendment could be a preventive paradox for population health by benefiting everyone. The latter could have implications for health disparities across subgroups of the population if differences exist across the outcomes benefiting from the fortification. Findings from existing studies on folic acid preand post-fortification suggest that there are disparities between groups. For instance, Ford and Bowman showed differences in red blood cell (RBC) folate concentrations between non-Hispanic blacks and nonHispanic whites with the highest differences among those with greater than a high school diploma regardless of gender. Conversely, differences between Mexican Americans and non-Hispanic whites were significant for men with at least 9 years of education and for women at the educational attainment extreme (<9 years of education and more than a high school diploma). Ganji and Kafai showed a decrease in prevalence of low RBC folate between 1988–94 and 1999–2002 across all racial/ ethnic and poverty-income ratio groups. However, nonHispanic blacks continue to exhibit a higher prevalence of low RBC folate through this period. Unlike previous studies examining trends between the preand post-fortification period, Dowd and Aiello focused on investigating the magnitude of the racial/ethnic and socioeconomic status (defined using poverty to income ratio) disparities assessed as absolute and relative differences. Using data from the National Health and Nutrition Examination Surveys (NHANES), Dowd and Aiello examined racial/ethnic and income disparities in folate status in US adults aged 25 years or older before (1991–1994) and after (1999–2002) enactment of the folic acid fortification. They found an increase in relative, but a decrease, in absolute difference before and after the fortification. Non-Hispanic blacks had 1.6 (95% CI: 1.4–1.9) greater odds of having low RBC folate (<362.6 nmol) levels compared with non-Hispanic whites in the pre-fortification period. This estimate was 3.7 (95% CI: 2.8–5.0) in the postfortification period. In the pre-fortification period, individuals in the bottom income quartile had a 1.3 (95% CI: 1.1–1.4) greater odds of having low RBC compared with those in the highest income quartile. Finally, in the post-fortification period, this estimate was 2.1 (95% CI: 1.6–2.7). The corresponding absolute differences were 233 (pre-) and 121 (post-fortification) Department of Health Sciences, Graduate Program in Public Health, Lehman College, CUNY, 250 Bedford Park Boulevard West, Gillet 336, Bronx, NY 10468, USA. E-mail: [email protected] Published by Oxford University Press on behalf of the International Epidemiological Association