Impact of a farmers' market healthy food subsidy on the diet quality of adults with low incomes in British Columbia, Canada: a pragmatic randomized controlled trial

Background: Adults with low incomes have lower diet quality than their higher income counterparts. In Canada, the British Columbia Farmers' Market Nutrition Coupon Program (FMNCP) provides coupons to low-income households to purchase healthy foods in farmers' markets.

Objective: The objective of this study was to examine the impact of the FMNCP on the diet quality of adults with low incomes.

Method: In a pragmatic randomized controlled trial conducted in 2019, adults with low incomes (≥18 y) were randomly assigned either to an FMNCP intervention (n = 143) or a no-intervention control group (n = 142). The FMNCP group received 16 coupon sheets valued at $21 per sheet over 10-15 wk to purchase healthy foods from farmers' markets. Participants completed a questionnaire and 2 24-h dietary recalls at baseline (0 wk), immediately post-intervention (10-15 wk), and 16-wk post-intervention (26-31 wk). Diet quality was calculated using the Healthy Eating Index-2015 (HEI-2015). Linear mixed-effects regression assessed differences in HEI-2015 total (primary outcome) and component scores (secondary outcomes) between the FMNCP and control groups at post-intervention and 16-wk post-intervention. Subgroup analyses examined program impacts by sex and age group (18-59 y, ≥60 y).

Results: There were no significant differences in HEI-2015 total scores between the FMNCP and control groups at post-intervention (-0.07; 95% CI: -4.07, 3.93) or 16-wk post-intervention (1.22; 95% CI: -3.00, 5.44) overall or between subgroups. There were no significant between-group differences in HEI-2015 component scores at post-intervention, although there were significant differences in component scores for dairy and fatty acids at 16-wk post-intervention.

Conclusion: The FMNCP did not significantly improve diet quality among adults with low incomes over the study period. Further research is needed to explore whether higher subsidy amounts or a longer intervention period is needed to meaningfully improve diet quality among adults with low incomes. This trial was registered at [clinicaltrials.gov] as [NCT03952338].