Urinary oxalate excretion in astronauts during long-duration spaceflight: an exploratory analysis

Authors

• Juliana Villanueva-Congote, Department of Urology, Massachusetts General Hospital, Boston, MA, USA.
• Stephanie Smith, University of Minnesota Medical School, Minneapolis, MN, USA.
• Nathaniel Hansen, Department of Urology, Brigham and Women's Hospital, Boston, MA, USA.
• Raeann Dalton, Division of Urologic Surgery, MaineHealth Maine Medical Center, Portland, ME, USA.
• Evelyn James, MaineHealth Maine Medical Center, Portland, ME, USA.
• Jay Buckey, Geisel School of Medicine at Dartmouth, Hanover, NH, USA.
• Daniel A. Wollin, Department of Urology, Brigham and Women's Hospital, Boston, MA, USA.
• David W. Sobel, MaineHealth Maine Medical Center, Portland, ME, USA.

Document Type

Article

Publication Date

10-16-2026

Institution/Department

Urology

Journal Title

BJU international

Abstract

OBJECTIVES: To explore the relationship between diet, mission phase, urinary calcium, and urinary oxalate during long-duration spaceflight. SUBJECTS AND METHODS: Dietary intake of calcium and oxalate and 24-h urine parameters from 12 astronauts during long-duration spaceflight while consuming controlled diets were analysed. Mixed-effects models assessed differences in urinary calcium and oxalate levels, adjusting for daily intake of calcium and oxalate, and for in-flight status relative to pre-flight status. RESULTS: From pre-flight to in-flight, median urinary calcium increased from 178.9 to 270.3 mg/day (P <  0.01) and urinary oxalate from 37.9 to 42.3 mg/day (P <  0.05). Post-flight, urinary calcium decreased to 185.8 mg/day (P <  0.01) and urinary oxalate to 31.5 mg/day (P <  0.01), relative to in-flight values. Dietary oxalate remained similar pre-flight and in-flight (382.0 vs 339.4 mg/day; P ≥ 0.05) but decreased post-flight to 241.6 mg/day (P <  0.01). Adjusted in-flight urinary oxalate was 10.71 mg/day higher than pre-flight and increased by 0.050 mg/day per 1-mg/day increase in dietary oxalate (95% confidence interval 0.036-0.064; P <  0.001); dietary calcium was not associated with urinary oxalate (P ≥ 0.05). CONCLUSIONS: Hyperoxaluria was observed during long-duration spaceflights and persisted throughout the in-flight phase under controlled dietary conditions. Although high dietary oxalate was the strongest predictor, evidence of inter-individual susceptibility was observed, with some astronauts exhibiting elevated oxalate pre-flight levels, which increased further during flight. Assessment of oxalate content in current astronaut food systems, mitigation of dietary oxalate load through timed calcium intake, and further investigation of microgravity-related effects on oxalate absorption and metabolism are required.

Recommended Citation

Villanueva-Congote, Juliana; Smith, Stephanie; Hansen, Nathaniel; Dalton, Raeann; James, Evelyn; Buckey, Jay; Wollin, Daniel A.; and Sobel, David W., "Urinary oxalate excretion in astronauts during long-duration spaceflight: an exploratory analysis" (2026). MaineHealth Maine Medical Center. 4706.
https://knowledgeconnection.mainehealth.org/mmc/4706