Dietary Guideline Adherence and All-Cause Mortality: A Target Trial Emulation of Universal and Equity-Targeted...

National dietary guidelines are key tools for chronic disease prevention, yet the mortality and life-expectancy benefits of greater guideline alignment remain insufficiently quantified overall and among socially disadvantaged groups.

A target trial was emulated in 2025 among adults ≥20 years using the Canadian Community Health Survey-Nutrition 2004 linked to mortality records through 2017. Alignment with Canada's Food Guide 2019 was retrospectively assessed using the Healthy Eating Food Index-2019 (HEFI-2019). Under prespecified target-trial assumptions of exchangeability, positivity, consistency, and approximation of random assignment, inverse-probability-weighted pooled logistic regression models estimated 5- and 13-year mortality risks under counterfactual scenarios shifting population diet to prespecified adherence levels. Targeted improvements were simulated among adults aged 45-80 years in equity-relevant subgroups defined by educational attainment, household income, food insecurity, or neighborhood deprivation.

Among 15,835 adults, shifting the population to optimal adherence yielded lower estimated 5-year (RR:0.55; 95% CI:0.39-0.77) and 13-year mortality (RR:0.79; 95% CI:0.70-0.89), corresponding to 13-year life-expectancy gains of 1.7 years (women) to 3.0 years (men). Targeting adults with less than secondary education lowered population-level 5-year mortality by 28% (RR_optimal:0.72; 95% CI: 0.56-0.93), comparable to universal high adherence among all adults aged 45-80 years (RR_high:0.64; 95% CI:0.47-0.87). Low-income targeting showed short-term within-group benefit only; estimates for food-insecurity and neighborhood-deprivation were near null.

Higher adherence to a national food-based dietary guideline yielded lower estimated mortality and longer life expectancy in this target trial emulation. Targeted improvement among adults with lower educational attainment showed clear short-term population-level benefit, comparable to universal approaches.