Do financial constraint and perceived stress modify the effects of food tax schemes on food purchases: moderation analyses in a virtual supermarket experiment

OBJECTIVE: To investigate whether financial constraint and perceived stress modify the effects of food-related taxes on the healthiness of food purchases.

DESIGN: Moderation analyses were conducted with data from a trial where participants were randomly exposed to: a control condition with regular food prices, an SSB tax condition with a two-tiered levy on the sugar content in SSBs (5-8 g/100ml: €0.21/l and ≥8g/100 ml: €0.28/l) or a nutrient profiling tax condition where products with Nutri-Score D or E were taxed at a 20 percent level. Outcome measures were: overall healthiness of food purchases (%), energy content (kcal) and SSB purchases (litres). Effect modification was analyzed by adding interaction terms between conditions and self-reported financial constraint or perceived stress in regression models. Outcomes for each combination of condition and level of effect modifier were visualized.

SETTING: Virtual supermarket.

PARTICIPANTS: Dutch adults (n = 386).

RESULTS: Financial constraint or perceived stress did not significantly modify the effects of food-related taxes on the outcomes. Descriptive analyses suggest that in the control condition, the overall healthiness of food purchases was lowest and SSB purchases were highest among those with moderate/high levels of financial constraint. Compared to the control condition, in a nutrient profiling tax condition the overall healthiness of food purchases was higher and SSB purchases were lower, especially among those with moderate/high levels of financial constraint. Such patterns were not observed for perceived stress.

CONCLUSION: Further studies with larger samples are recommended to assess whether food-related taxes differentially affect food purchases of subgroups.