High prevalence of ascorbate deficiency in an Australian peritoneal dialysis population.

BACKGROUND: An adequate total body pool of ascorbate is essential for optimum health in humans. Requirements for ascorbate are increased in peritoneal dialysis (PD) patients most likely due to a combination of poor nutrition and increased dialysate losses.

METHODS: We measured serum ascorbate levels in 45 clinically stable PD patients to assess the prevalence of ascorbate insufficiency (level between 2 and 4 mg/L) and deficiency (level <2 mg/L). We also assessed the efficacy of subsequent supplementation and patients' adherence to the prescribed supplementation. All patients were advised on commencement of dialysis to take a multivitamin tablet containing 100-120 mg ascorbate.

RESULTS: Eighteen (41%) PD patients were regularly taking ascorbate-containing multivitamins, while 27 (59%) patients did not take ascorbate supplements. Serum ascorbate levels ranged from <0.2 to 41 mg/L, with wide variations in serum ascorbate at any given intake level. Ascorbate deficiency was present in 1/3 of the current PD population (44% of patients not taking supplements and in 16% of those on supplements), although none of the patients demonstrated clinical manifestations of scurvy. Targeted supplementation of ascorbate insufficient patients increased the median serum ascorbate level from 1.7 mg/L (IQR 1.2-2.2) to 22.5 mg/L (IQR 16.7-32.9).

CONCLUSION: Our results show that, in PD patients, ascorbate deficiency is common and can readily be identified with serum ascorbate measurements. Oral supplements in the form of inexpensive multivitamin preparations restore adequate serum ascorbate levels in the majority of these patients. We therefore suggest measurement of ascorbate levels in all PD patients at the commencement of dialysis with a target level in the normal range (4-14 mg/L).