Abstract: A method for alleviating arthritis includes administering to a subject in need thereof a postbiotic extract. The postbiotic extract is prepared by a process including the steps of providing a first material having a first isoelectric point ranging from pH 1 to pH 6 and a second material having a second isoelectric point ranging from pH 4 to pH 8, admixing the first material and a probiotic microorganism with water having a pH greater than the second isoelectric point, so as to forma mixture, adding the second material into the mixture and then adjusting a pH of the second material-added mixture to between the first and second isoelectric points so that a precipitate is formed, and subjecting the precipitate to a cell wall isolation treatment to obtain the postbiotic extract.