GSTM1 and chronic kidney disease: There were significant differences in age, sex, race, family PIR, education level, marital status, smoking status, alcohol consumption status, hypertension, DM, CHF, stroke, CKD, BMI, waist circumference, RBC, Hb, serum iron, calcium, phosphorus, mean energy intake, protein intake, folic acid intake, vitamin B12 intake, and iron intake among the Q1, Q2, Q3, and Q4 groups.