The paper presents the results of the study aimed to evaluate whether prolonged consumption of a probiotic drink consisting of protective microorganisms (lactobacilli, enterococci, bifidobacteria) and fermented from Saccaromyces would be beneficial to the human microbiological status and gastrointestinal tract (GIT) functioning. Ten volunteers (2 males and 8 females above 50 years of age) consumed the drink over the period of three months. We investigated microflora of the intestine, upper airway (UA) and vagina (in females). Microbial samples from the intestine and UA were gathered 4 times: a week prior to the experiment and then in every 30 days. Samples of the vaginal discharge were taken 7-10 days prior to the experiment and in 7–10 after its completion. Evaluation of the gastric emptying function, hydrochloric acid production, fasting volume of the gastric juice and GIT electrical activity was performed at these time points also. The experiment revealed positive trends of the intestinal microflora. Changes in the species and quantitative composition of the UA microflora were less pronounced as in the first half of the experiment changes in the UA microflora were more like negative and displayed a marked positive trend in the second half. After the course of probiotic prophylaxis, colonization of the vagina and cervical channel by opportunistic microorganisms was reduced in 6 out of 8 females. In addition, the probiotic drink stabilized the electrical activity of all GIT components and enhanced intestinal peristalsis.