Mobile grocery stores show no demonstrated improvement in diet quality in a randomized trial

Food access tested at twelve housing sites

The Twin Cities Mobile Market is a grocery store on wheels designed to offer nutritious, low-cost food in low-income neighborhoods with limited food access. Researchers randomly assigned twelve subsidized housing sites in Minneapolis–Saint Paul to a weekly service or a waiting list.

Among the adults enrolled, 242 completed baseline assessments. Their mean age was 66.5 years. Follow-up assessments began after six months of service. The primary outcome was overall diet quality, measured using the Healthy Eating Index-2020 based on 24-hour dietary recalls.

No demonstrated benefit on the primary outcome

The primary analysis found no statistically significant difference in diet quality between the groups. The adjusted difference was 1.25 points, with a confidence interval ranging from −1.60 to 4.10. This uncertainty allows neither a claim of improvement nor a conclusion that there was no effect at all.

Six of the seven secondary outcomes also showed no significant differences, including fruit and vegetable intake, energy intake, added sugars and food security. However, participants at sites receiving the service consumed an average of 397 mg less sodium per day than those on the waiting list, with a confidence interval corresponding to a reduction of 158–636 mg.

This finding concerns dietary intake, not a demonstrated clinical improvement. The abstract reports no findings on blood pressure or cardiovascular events.

A well-liked service, but used by only some participants

At sites receiving the service, 43.1% of participants had made at least one purchase at the market during months five and six. Among those who reported having used it, 95.7% said they would recommend it. Satisfaction and a measured improvement in diet are therefore two distinct outcomes.

The primary analysis evaluates the provision of the service at the housing sites, not its regular use by each resident. Limited use could contribute to the overall result, but the abstract does not allow this explanation to be confirmed.

A per-protocol sensitivity analysis also found a higher proportion of calories from added sugars in the intervention group. This signal is a reason not to focus solely on the reduction in sodium.

What we can take away

This trial does not demonstrate that a weekly mobile grocery store alone improves overall diet quality at these housing sites. The reduction in sodium deserves attention, but does not constitute evidence of clinical benefit.