Studying the impact of SNAP on dietary quality presents a challenge because of selection bias; SNAP participants often are worse off than eligible nonparticipants with respect to financial and nutritional needs (Martin et al., 2012; Nord and Golla, 2009). Because SNAP participants and nonparticipants may not be sufficiently comparable, it is difficult to determine whether observed differences are due to the program or to unobserved differences between the groups, such as a family’s economic situation, nutritional needs, health status, food security status, or motivation to enroll in the program. Evidence reviewed by the committee related to the association between SNAP and diet quality was inconclusive. Some studies suggest that SNAP improves the quality of the diet (Basiotis et al., 1998; Lee et al., 2006; Mabli et al., 2010; Rose et al., 1998), while others suggest that it does not (Chen et al., 2005; Cole and Fox, 2008; Fox et al., 2004; Wilde et al., 1999; You et al., 2009). Because of the confounding effect of a self-selection bias among the SNAP population, using analysis of diet quality to inform a definition of the adequacy of SNAP allotments may not be feasible.
Most recently, debates over restrictions of SNAP purchases have focused largely on whether the purchase of sugar-sweetened beverages (SSBs) should be permitted (Brownell and Ludwig, 2011). Evidence is limited on patterns of beverage purchases among SNAP recipients. Andreyeva and colleagues (2012) collected grocery store scanner data from January to June 2011 and concluded that SSBs account for 58 percent of beverage purchases made by SNAP households. Their data and analysis are limited, however, by a regional focus on a single grocery chain in New England and the inclusion of only SNAP households with a history of recent participation in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). Further, purchases of SSBs accounted for 5 and 7 percent of total grocery spending by SNAP and WIC households, respectively, and 9 and 7 percent, respectively, of total spending on all beverage refreshment categories (Andreyeva et al., 2012). Many arguments have been made for and against the policy of restricting SNAP purchases of SSBs (Brownell and Ludwig, 2011; FNS, 2007). The following discussion summarizes only those related to access to a healthy diet (e.g., whether allowing for the purchase of SSBs with SNAP benefits contributes directly to an unhealthy diet).
Economic theory suggests that restricting the purchase of some items, such as SSBs, might not impact the overall purchasing behavior of SNAP recipients. SNAP was designed to supplement participants’ food purchases,