Cost of a Healthy Diet: A Population-Representative Comparison of 3 Diet Cost Methods in Canada

Background

Different food price sources and dietary assessment tools may impact the estimation of diet costs and hamper our understanding of the relationship between diet costs and dietary intakes.

Objectives

We aimed to investigate the effect of 3 diet cost derivation methods, with increasing numbers of food prices and geographic specificity, holding consistent the dietary assessment tool, on the estimation of diet costs overall and by food group.

Methods

We matched 24-h dietary recall data from the 2015 Canadian Community Health Survey-Nutrition (CCHS-N) to food price data from 3 Canadian Consumer Price Index (CPI) food price lists; national short list, national long list, and provincial long list. We compared the daily ($/day) and energy-adjusted ($/2000 kcal) diet costs overall and by food groups for the overall population (4+), children (4–18), and adults (19+).

Results

The proportion of dietary intakes (grams) that were covered by CPI prices significantly increased from the national short list to the national long list but did not significantly differ from the national long list to the provincial long list. The national short list resulted in the highest daily and energy-adjusted diet costs overall. No difference in diet costs was noted between the national and provincial long lists. Diet costs for 4 food groups—additions, sweets, fruits, and vegetables, which were poorly covered by the national short list—significantly differed using the national and provincial long lists. All 3 diet cost methods were significantly correlated with energy intakes; however, a strong/very strong correlation was detected for children, and a weak/moderate correlation for adults.

Conclusions

The choice of food price data may introduce bias in the diet cost estimate, as well as limiting our understanding of how individuals allocate their diet costs. Refinement of diet cost estimation methodology and measures can strengthen future studies of how consumers allocate their purchases to their diets.