Association of low potassium diet and folic acid deficiency in patients with CKD

BACKGROUND Most of the folic acid sources are rich also in potassium. Patients with chronic kidney disease (CKD) usually receive a low potassium diet. We investigated the possibility of an association between low potassium diet and folic acid deficiency. METHODS In total, 128 CKD patients participated in this cross-sectional study. Sixty-four patients with CKD grades 1 and 2 were on an unrestricted potassium diet when enrolled in the study, and 64 patients with CKD grades 3 and 4 had received instructions to restrict their intake of potassium at least 6 months before enrollment in the study. Subjects were evaluated for daily intake of folic acid (DIFA), daily intake of potassium (DIK), and serum folic acid levels (SFA). RESULTS DIFA correlated with the estimated glomerular filtration rate, the DIK, and the SFA (P<0.001). SFA correlated with the estimated glomerular filtration rate (P<0.001). Mean DIFA and mean SFA were lower among patients with CKD grades 3 and 4 than among those with CKD grades 1 and 2 (P<0.001). The mean DIFA in patients with folic acid deficiency was lower than that in those with SFA ≥7.1 nmol/L (P<0.001). There was lower SFA and threefold greater frequency of folic acid deficiency among patients with CKD grades 3 and 4 who had received instructions to restrict their intake of potassium than among patients with CKD grades 1 and 2 who were on an unrestricted potassium diet. CONCLUSION A potassium-restricted diet offered to patients with CKD grades 3 and 4 may be associated with folic acid deficiency. Serum levels of folic acid should be investigated before starting potassium restriction in patients with CKD grades 3 and 4, in order to identify individuals with folic acid deficiency or with marginal serum levels who should receive folic acid replacement therapy.