This is a longitudinal study with a randomized crossover design, double-blind, placebo-controlled, and with washout period. Thirty non-dialysis patients of both genders, aged between 18 and 60 years and with CKD stage3-4 (glomerular filtration rate \< 59 mL/min/1.73 m2) will be included in the study. Pregnant patients, smokers and those under use of antibiotics in the last 3 months, or in use antithrombotic, pre-, pro- or synbiotic supplements, antioxidant supplements or habitual cranberry intake will be excluded. In addition, those with autoimmune and infectious diseases, cancer, liver diseases and HIV will also not be included in the study. The patients that fulfill the eligible criteria and sign the ethical informed consent will be randomized to either Group A (Cranberry) or Group B (Placebo). During 12 weeks, patients allocated in group A will receive capsules containing cranberry extract (Vaccinium macrocarpon to 25% anthocyanosides 160mg, equivalent to 40mg anthocyanosides), once daily (lunch), totaling 500mg / day and those allocated in the group B will receive a placebo (500mg of corn starch). After the supplementation period, a 12-week washout will be performed for subsequent crossover of the supplement. The randomization will be computed in the ratio of 1: 1, with block size of 15 (Cranberry group and Control), to receive cranberry or placebo. This project was approved by the Ethics Committee of the Faculty of Medicine-UFF, n. 2.653.752.
