SNAP and Diet Quality: An Instrumental Variables Approach

Recent research has shown that the Supplemental Nutrition Assistance Program (SNAP) is effective in reducing food insecurity. Questions remain, however, about whether SNAP also has any effects on the quality of low-income households’ diets. These questions have surfaced in the context of the increasing public costs of diet-related illnesses like diabetes, dyslipidemia, and heart disease. Policy recommendations to restrict what can be purchased with SNAP benefits are evidence of these concerns. We use a unique data set that matches state-level SNAP policy variables to individual level data in three waves of the National Health and Nutrition Examination Survey (NHANES). We examine Healthy Eating Index (HEI) scores and intakes of macro-nutrients for low-income households that do and do not participate in SNAP. We find that, after controlling for observed and unobserved factors, SNAP recipients had overall diet quality comparable to their counterparts, although most differences are in the favor of non-participants. While SNAP purchase restrictions could improve diet outcomes, they might do so at the cost of impairing the effectiveness of SNAP at reducing food insecurity.