Fibroblast Growth Factor-23 (FGF-23) Levels Differ Across Populations by Degree of Industrialization.

Context: Compensatory increases in fibroblast growth factor 23 (FGF23) with increasing phosphate intake may adversely impact health. However, population and clinical studies examining the link between phosphate intake and FGF23 levels have focused mainly on populations living in highly industrialized societies in which phosphate exposure may be homogenous.

Objective: The objective of the study was to contrast dietary phosphate intake, urinary measures of phosphate excretion, and FGF23 levels across populations that differ by the level of industrialization.

Design: This was a cross-sectional analysis of three populations.

Setting: The study was conducted in Maywood, Illinois; Mahé Island, Seychelles; and Kumasi, Ghana.

Participants: Adults with African ancestry aged 25-45 years participated in the study.

Main Outcome: FGF23 levels were measured.

Results: The mean age was 35.1 (6.3) years and 47.9% were male. Mean phosphate intake and fractional excretion of phosphate were significantly higher in the United States vs Ghana, whereas no significant difference in phosphate intake or fractional excretion of phosphate was noted between the United States and Seychelles for men or women. Overall, median FGF23 values were 57.41 RU/mL (interquartile range [IQR] 43.42, 75.09) in the United States, 42.49 RU/mL (IQR 33.06, 55.39) in Seychelles, and 33.32 RU/mL (IQR 24.83, 47.36) in Ghana. In the pooled sample, FGF23 levels were significantly and positively correlated with dietary phosphate intake (r = 0.11; P < .001) and the fractional excretion of phosphate (r = 0.13; P < .001) but not with plasma phosphate levels (r = -0.001; P = .8). Dietary phosphate intake was significantly and positively associated with the fractional excretion of phosphate (r = 0.23; P < .001).

Conclusion: The distribution of FGF23 levels in a given population may be influenced by the level of industrialization, likely due to differences in access to foods preserved with phosphate additives.