Association between dietary phosphate, dietary calcium, and calcium to phosphate ratio on serum fibroblast growth factor-23 concentrations

Introduction: The aim of this study is to determine the association between dietary phosphate (DP), dietary calcium (DC), and calcium to phosphate ratio (DC:DP) on fibroblast growth factor-23 (FGF23) levels across three African-origin populations (Chicago, IL n=421; Kumasi, Ghana n=468; and Mahé, Seychelles n=300). Higher levels of FGF23 are associated with increased risk of cardiovascular disease.

Methods: The study population includes 1,189 healthy adults 25-45 years of age. FGF23 levels were measured in fasting blood samples. DP and DC were determined by 24-hour recalls. Spearman rank correlation coefficients were calculated for all variables. Logistic regression models were used to examine the association between DC, DP, and DC:DP, and FGF23 value ≥50 RU/mL while adjusting for age, gender, location, BMI, and 25[OH]D levels.

Results: The participants were 47% male. Median FGF23 levels were US=58.4 RU/mL (IQR 43.7-78.5), Ghana=33.9 RU/mL (IQR 25.1-49.2), and Seychelles=46.9 RU/mL (IQR 36.8-60.7). FGF23 was positively correlated with DP (r=0.10; P < 0.001), DC (r=0.22; P < 0.001) and DC:DP (r=0.23; P < 0.001). Every unit change in DC:DP increased the odds of having a FGF23 value above the median ( ≥50 RU/mL by 3.7 fold (95% CI 1.8-7.8)).

Discussion: Our study shows that both DP and DC influence FGF23 levels, a risk factor for cardiovascular disease. Further research is needed to determine the upper tolerable levels of both calcium and phosphate intake for optimal health. Policymakers should create nutrition composition guidelines for food manufacturers to improve the micronutrient imbalance and reduce mineral-dense products in the food supply.