Process Evaluation of a Farm-to-WIC Intervention

Despite the promise of farm-to-institution interventions for addressing limited vegetable access as a barrier to intake, programs designed for the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) are lacking. As such, little is known about the implementation of, and mechanisms of action through which, farm-to-WIC interventions affect vegetable intake and participant satisfaction with such programs.

To examine whether a farm-to-WIC intervention to promote vegetable intake was implemented as intended, differences between participants who received the intervention relative to those in a usual-care control group in intermediate outcomes of vegetable-related knowledge, attitudes, and behaviors, and secondary outcomes of physical activity and weight status; and participant satisfaction with the intervention.

A process evaluation encompassing descriptive and comparative analyses of implementation fidelity logs and survey data collected as part of a pilot study was conducted.

The setting was a large, New Jersey-based, urban WIC agency. Recruited between June 3 and August 1, 2019 through 3 of the agency's 17 sites (1 intervention and 2 control sites), participants were 297 primarily Hispanic adults (160 enrolled at the intervention site and 137 at control sites).

The intervention combined behaviorally focused instruction and handouts with the introduction of a WIC-based farmers' market, field trips to an area farmers' market, telephone coaching and support, and recipe demonstrations and tastings.

Primary outcomes were vegetable intake (measured via self-report and objectively using dermal carotenoids as a biomarker of intake) and the redemption of vouchers provided by WIC for fruit and vegetable purchases at farmers' markets (measured objectively using data provided by WIC). For the process evaluation, logs were used to document program activities. Vegetable-related knowledge, attitudes, and behaviors, physical activity, and satisfaction with the intervention were assessed with participant questionnaires. Weight status was assessed with direct measures of height and weight. Data were collected at baseline and at mid- and post-intervention (3 and 6 months post-baseline, respectively).

Descriptive statistics were used to characterize implementation fidelity. Associations between intermediate and secondary outcomes and vegetable intake were examined at baseline with Pearson correlations. Post-baseline between-group differences in the outcomes were examined with linear mixed-effects models adjusted for baseline values and covariates. Satisfaction with the intervention was assessed with inferential and thematic analyses.

Post-intervention, measures of vegetable intake were higher in the intervention relative to the control study group. Receipt of the intervention was also associated with a greater likelihood of voucher redemption. Nearly all participants (≥94%) received the intervention as intended at the WIC-based farmers' market; smaller percentages completed 1 or more planned trips to the area farmers' market (28%) and telephone coaching and support calls (88%). Although most intermediate and secondary outcomes were associated with measures of vegetable intake at baseline, the variables did not differ between study groups post-intervention. Mean satisfaction ratings were ≥6.8 on a 7-point scale. Recipe demonstrations, learning about vegetables, field trips, and the rapport with staff were liked most about the program. Although adding days and times for field trips was suggested, limited market days and hours of operation limited the ability to do so.

Preliminary data highlight the promise of this well-received intervention. Intermediate outcome findings suggest that other potential intervention mechanisms of action should be considered in future large-scale trials of this program. Broad-scale initiatives are needed to improve access to farmers' markets in underserved communities.