This study examined the association between household food security and social isolation among US adults and differences by age. To evaluate their joint impact on health, we examined whether both experiences are independently associated with less healthy functioning across intrinsic capacity (IC) domains, and whether social isolation modifies the food security-IC relationships.

Data were from 14,570 non-institutionalized adults ≥20 years from the 2007 to 2018 National Health and Nutrition Examination Surveys. Food security was measured using the US Household Food Security Survey Module. Social isolation was measured with a composite score capturing marital status, household size, and social participation. IC encompassed five domains: cognition, vitality, locomotion, sensory function, and psychological well-being. Multivariable logistic regressions examined these associations, adjusting for sociodemographic and health covariates.

Compared to high food security, marginal food security (OR 1.29, 95% CI 1.05–1.60), low food security (OR 1.36, 95% CI 1.08–1.71), and very low food security (OR 1.95, 95% CI 1.61–2.37) were associated with greater social isolation after multivariable adjustment. This association was more robust among adults ≥40 years. Among adults ≥40 years, food insecurity and social isolation independently predicted with less healthy functioning across all IC domains. Across most domains, social isolation did not significantly modify the food security-IC associations.

There was a graded association between food insecurity and social isolation after accounting for social disadvantage. Both experiences independently predicted lower IC. These findings underscore the need for public health interventions to address food insecurity and social isolation to better promote healthy aging.