Effect of yogurt administration on human intestinal bacterial flora and biochemical analysis of blood

To determine whether ingestion of yogurt would alter the human intestinal bacterial flora, 17 healthy adult volunteers were studied. Three daily meals were supplied by the hospital dietary department during the 6 weeks of experimental period, including an initial one week without yogurt (control period), 4 weeks with two bottles (230 gm each) of BL-yogurt per day (Wei-Chuan Food Co.) (administration period), and one week without yogurt (follow-up period). The subjects were asked to record their own fecal characteristics, defecation frequency and the total weight of feces every day. The body weights and biochemical findings in the blood of subjects were also examined before and after yogurt administration. For the investigation of the intestinal bacterial flora, stool samples were taken once per week and sent to the laboratory promptly. The total aerobic bacteria, total anaerobic bacteria, Bifidobacterium spp, Lactobacillus spp, E. coli, and Clostridium perfringes of each fresh stool sample were analyzed by dilution and cultured on proper agar plates. The number of bacteria was determined as colony-forming units per gram of stool. Results indicated that there were no side effects or discomfort complaints in any of the cases during the BL-yogurt administration period. Biochemical findings such as hemoglobin, hematocrit, sugar, lipid in blood did not change. However, ingestion of BL-yogurt significantly increased the probiotic Bifidobacterium spp count, while harmful E. coli was suppressed. Even during the last week when yogurt consumption was discontinued, the ratio between Bifidobacterium spp. to E. coli was still elevated. In conclusion, ingestion of yogurt increased the number of stool bifidobacteria and suppressed E. coli.