Urinary Citrate, an Index of Acid-Base Status, Predicts Bone Strength in Youths and Fracture Risk in Adult Females.
Diet can impact on bone strength via metabolic shifts in acid-base status. In contrast to the strongly diet-dependent biomarker urinary potential renal acid load (uPRAL), the amount of renally excreted citrate integrates nutritional and systemic influences on acid-base homeostasis with high citrate indicating prevailing alkalization.



To examine the association between urinary citrate excretion and bone strength as well as long-term fracture risk.



Prospective cross-sectional analysis; 231 healthy children (6-18 y) of the Dortmund Nutritional and Anthropometric Longitudinally Designed Study were included, with at least 2 urine collections available during the 4 years preceding peripheral quantitative computed tomography (pQCT) of the nondominant proximal forearm. uPRAL, urinary citrate, and urinary nitrogen excretion were quantified in 857 24-hour urine samples. Data on overall fracture incidence were collected within a 15-year follow-up after pQCT measurement.



Parameters of bone quality and geometry (pQCT) as well as long-term fracture incidence.



After controlling for confounders, especially forearm length, muscle area, and urinary nitrogen (biomarker of protein intake), urinary citrate excretion was positively associated with various parameters of bone quality and geometry (P < .05). Fracture risk in adult females, but not in males, was inversely associated with urinary citrate and positively with uPRAL (P < .05).



Although urinary citrate has to be confirmed as an integrated noninvasive biomarker of systemic acid-base status in further studies, our results substantiate dietary and metabolic acidity as potentially adverse for bone health in the long run from childhood onward.
DONALD Study Dortmund (J.E., S.J., L.S., T.R.), Department of Nutritional Epidemiology, Institute of Nutritional and Food Sciences (IEL), University of Bonn, 44225 Dortmund, Germany; and Children's Hospital (E.S.), University of Cologne, 50937 Cologne, Germany.
Jonas
J
Esche
DONALD Study Dortmund (J.E., S.J., L.S., T.R.), Department of Nutritional Epidemiology, Institute of Nutritional and Food Sciences (IEL), University of Bonn, 44225 Dortmund, Germany; and Children's Hospital (E.S.), University of Cologne, 50937 Cologne, Germany.
Simone
S
Johner
DONALD Study Dortmund (J.E., S.J., L.S., T.R.), Department of Nutritional Epidemiology, Institute of Nutritional and Food Sciences (IEL), University of Bonn, 44225 Dortmund, Germany; and Children's Hospital (E.S.), University of Cologne, 50937 Cologne, Germany.
Lijie
L
Shi
DONALD Study Dortmund (J.E., S.J., L.S., T.R.), Department of Nutritional Epidemiology, Institute of Nutritional and Food Sciences (IEL), University of Bonn, 44225 Dortmund, Germany; and Children's Hospital (E.S.), University of Cologne, 50937 Cologne, Germany.
Eckhard
E
Schönau
DONALD Study Dortmund (J.E., S.J., L.S., T.R.), Department of Nutritional Epidemiology, Institute of Nutritional and Food Sciences (IEL), University of Bonn, 44225 Dortmund, Germany; and Children's Hospital (E.S.), University of Cologne, 50937 Cologne, Germany.
Thomas
T
Remer
D000293:Adolescent; D000328:Adult; D002648:Child; D019343:Citric Acid / Q000652:urine*; D003430:Cross-Sectional Studies; D005260:Female; D005542:Forearm / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D050723:Fractures, Bone / Q000652:urine*; D006801:Humans; D008297:Male; D012306:Risk
D019343:Citric Acid