2255 THE IMPACT OF FISH OIL SUPPLEMENTATION ON ENDOGENOUS OXALATE SYNTHESIS AND URINARY OXALATE EXCRETION

Abstract

INTRODUCTION AND OBJECTIVES: It has been recently reported that the administration of fish oil supplements to non-hyperoxaluric, healthy adults consuming metabolic diets with normal oxalate and calcium content resulted in a significant reduction in urinary oxalate excretion. The mechanism of this response has not been defined, but we hypothesize that it is due to a reduction in endogenous oxalate synthesis via its anti-inflammatory and antioxidant properties. METHODS: Fifteen healthy, non-stone forming, non-hyperoxaluric adults participated (mean age 25.3 2.7 years, BMI 30, 8 male, 7 female) in this study. First, subjects were asked to abstain from utilization of any supplements, vitamins, medications, or foods enriched in omega 3 fatty acids for thirty days. After this, they collected two random baseline 24 hour urine specimens while eating a self-selected diet. Next, the subjects consumed a controlled low oxalate diet for five days. This was intended to reflect baseline endogenous oxalate production. The diet contained 50 mg oxalate, 1000 mg calcium, 3500 mg sodium, 300 mg magnesium, 1500 mg phosphorus, 3000 mg potassium, 125 mg vitamin C, and 2.5 liters of fluid per day. Subjects collected three 24 hour urine specimens on days three through five of this controlled diet phase. Next, they began taking two fish oil supplement capsules twice daily for 30 days (2600 mg eicosapentaenoic acid and 1800 mg docosahexaenoic acid per day) while consuming selfselected diets for 25 days. On days 26-30, they continued on fish oil and consumed the aforementioned controlled low oxalate diet. They collected 24 hour urine specimens on days 28-30. Statistical analysis included repeated measures ANOVA and Student’s t test. RESULTS: Analysis of the 24 hour urine collection data revealed no significant differences in urine volume, creatinine, or calcium between the baseline and metabolic dietary phases without and with fish oil. ANOVA analysis of daily oxalate excretion was significant (p 0.01). While the Student’s t test revealed a significant decrease in oxalate excretion between the self-selected diet and both controlled dietary phases (p 0.01), there was no significant difference between the controlled diet phases without or with fish oil supplementation. CONCLUSIONS: These results suggest that fish oil supplementation does not impact endogenous oxalate synthesis in healthy adults without hyperoxaluria. Thus, the reduction previously reported in this cohort could be due to alterations in gastrointestinal or renal handling of oxalate.