Introduction: Elevated Fibroblast Growth Factor 23 (FGF23) - an endocrine hormone linked to cardiovascular and kidney disease outcomes - is a compensatory response to high dietary phosphate load or chronic kidney disease. Large quantities of inorganic phosphates additives are found in processed foods, and food insecurity is associated with higher consumption of processed foods.
Hypothesis: We hypothesized that developing food insecurity is associated with an increase in FGF23.
Methods: We included CARDIA study participants with a stored plasma sample available from at least two consecutive exams at years 20, 25, and 30 (N=3,421). Food insecurity was assessed through a single question about ability to afford quantity and quality of food. FGF23 levels were assessed using a commercial c-terminal ELISA. Due to a strong right skew in FGF23 levels, we divided FGF23 in quartiles and compared the highest quartile to the combined lower three quartiles using logistic regression. Econometric fixed effects models that adjust by design for all time-invariant covariates were used to model the longitudinal association between simultaneous within-person change in food insecurity and FGF23. Due to an interaction between food insecurity and race (p=0.002), we stratified by race.
Results: About 29% of blacks and 14% of whites experienced change in food insecurity during follow-up. Developing food insecurity was associated with a 1.46 greater odds of increasing to the highest quartile of FGF23 (95% CI: 1.02,2.10) among blacks; however, there was no significant longitudinal association among whites (OR=1.05; 95% CI: 0.62,1.77).
Conclusions: Using models that tightly control for all time-invariant confounding, we found that developing food insecurity was associated with increases in FGF23 among blacks. The differential increases in blacks as compared to whites may be due to differences in dietary changes in response to developing food insecurity. Previous research has shown racial differences in dietary quality by food insecurity.