Moderate dietary vitamin C supplement does not affect urinary oxalate concentration in cats

Abstract

To investigate the effect of dietary vitamin C supplement on urinary oxalate concentration in cats, 48 adult American Domestic Short Hair cats were stratified into four groups based on body weight, age, and sex, 12 cats in each group. Cats were fed a nutritionally complete and balanced dry control food for 2 weeks before they were fed one of the four foods (the control food, food 1, food 2, and food 3) for additional 4 weeks. Foods 1–3 were made by supplementing the control food with l‐ascorbyl‐2‐polyphosphate, a stable form of vitamin C. Analysed vitamin C was 40 mg/kg, 78 mg/kg, 106 mg/kg, and 193 mg/kg in the control food, food 1, food 2, and food 3 respectively. Fresh tap water was always available to cats. At the end of the study, dietary vitamin C supplement up to 193 mg/kg did not affect urinary oxalate concentration in cats, even after correction by urinary creatinine excretion (Table 1).There was a positive linear correlation between vitamin C intake and vitamin C concentrations in the serum (r = 0.65, p < 0.01) and urine (r = 0.33, p = 0.023) but not urinary oxalate concentration (r = –0.07, p = 0.658). Average daily food intake and body weight were similar among dietary groups during the study. In conclusion, dietary vitamin C supplement up to 193 mg/kg does not affect urinary oxalate concentration in cats. Measurements in cats fed various amounts of vitamin C for 4 weeks Dietary groups Control Food 1 Food 2 Food 3 p‐values Dietary Vitamin C (mg/kg) 40 78 106 193 Body weight (kg) 3.7 ± 0.3 3.8 ± 0.3 3.6 ± 0.4 3.8 ± 0.3 0.445 Food intake (g/day) 40 ± 5 40 ± 6 39 ± 6 40 ± 7 0.950 Vitamin C intake (mg/day) 1.6 ± 0.2 3.1 ± 0.4 4.1 ± 0.6 7.7 ± 1.4 <0.01 Serum vitamin C (μg/ml) 1.5 ± 0.8 2.1 ± 1.0 2.3 ± 0.5 3.4 ± 0.6 <0.01 Urine vitamin C (μg/ml) 5.3 ± 7.1 4.7 ± 3.9 12.8 ± 11 15 ± 14 0.026 Urine oxalate (mM) 0.73 ± 0.1 0.77 ± 0.1 0.74 ± 0.2 0.74 ± 0.2 0.895 Urine oxalate/creatinine 1.6 ± 0.4 1.8 ± 0.3 1.8 ± 0.3 1.9 ± 0.3 0.316 Values in the table are mean ± SD, n = 12; p‐values: GLM analysis