Fibroblast Growth Factor-23 and a Vegetarian Diet

Objective: Sparse data exist on population distributions of serum fibroblast growth factor-23 (FGF23) levels from developing, middle-income economies. FGF23 levels may differ substantially across regions based on differences in diet and urbanization. In a population-based study from North India, we tested the hypothesis that urinary phosphate excretion and FGF23 levels are lower among rural compared with urban participants, and among vegetarian compared with nonvegetarian participants.

Methods: We measured 24-hour urinary phosphate, and serum parathyroid hormone and FGF23 in a subsample of the population-based Cardiometabolic Risk Reduction in South Asia and Indian Council of Medical Research Coronary Heart Disease surveys. We categorized participants according to diet and residence: urban nonvegetarians (n = 70), urban vegetarians (n = 564), and rural vegetarians (n = 558). Using least square means, we compared the groups' 24-hour urinary phosphate (with urban vegetarians as reference) and FGF23 levels after accounting for age, sex, diabetes, and body mass index.

Results: Among 1,192 study participants, mean FGF23 was 41 ± 18 pg/mL, median parathyroid hormone was 44 (interquartile range [IQR] 31-60) pg/mL, and median 24-hour urinary phosphate excretion was 419 (IQR: 47-622) mg/day. Urinary phosphate was significantly higher in rural compared with urban vegetarians (median, 503; IQR, 334-543 versus 365; IQR, 199-399 mg/day), but adjusted mean FGF23 levels did not differ across study groups.

Conclusion: In rural and urban India, urinary phosphate excretion was low, but FGF23 levels did not differ by residence or dietary preference. Homogenously low dietary phosphate intake across different settings and diets may partly explain the lack of differences in FGF23.