Background: Leaky gut, or intestinal permeability, is the phenomenon of the gut wall exhibiting increased absorbency. It is pretty well recognised that an altered or damaged bowel lining or gut wall may result from unbalanced diet, parasites, infection, or medications and that this allows substances such as toxins, microbes, undigested food, or waste to leak through. As a natural consequence, this prompts the body to initiate an immune reaction leading to potentially severe health conditions. Different strategies may be used to improve, at least temporarily, the physiological intestinal barrier. The use of specific beneficial microorganisms, such as lactobacilli and bifidobacteria, has been suggested as an innovative tool to counteract an improper level of intestinal permeability. The association of bacteria with specific gelling agents, such as gums, may represent an improvement since these molecules are able to form hydrophilic gels that distribute uniformly over the inner intestinal surface. This pilot study was undertaken to evaluate intestinal permeability in subjects treated with a gelling complex, an association of tara gum and the microorganism Streptococcus thermophilus ST10 (DSM 25246), which has a well-demonstrated in vitro ability to synthesise and secrete exopolysaccharides (EPSs)., Methods: Twenty-five healthy subjects were enrolled in this human intervention, double-blind, placebo-controlled, pilot trial (age between 21 and 57 y, mean 37.7±11.2). Subjects were then randomised into 2 groups: group A (13 subjects) was given an active formulation containing 250 mg of tara gum and 1 billion viable cells of S. thermophilus ST10, whereas group B (12 subjects) was given a placebo formulation. All the subjects participating in the study were directed to take 1 dose per day for 30 consecutive days. The presence and concentration of exopolysaccharides (EPSs) in the faeces was determined at time 0 (d0), after 30 days of treatment (d30), and at the end of the 2-week follow-up period (d45). The monosaccharide composition of EPSs was used to quantify the possible contribution of tara gum to the amount of polysaccharides detected in the faecal material. Intestinal permeability was evaluated at the same time by means of the lactitol/mannitol ratio (small intestine permeability) and sucralose concentration (colonic permeability) in urine specimens sampled after specified times. A statistical comparison was made between the concentration of EPSs, the lactulose/mannitol ratio, and the amount of excreted sucralose in the 2 groups at d0, d30, and d45., Results: In the active group, supplementation with S. thermophilus ST10 and tara gum was able to significantly increase the faecal EPSs concentration compared with placebo (from 0.169 mg/g to 0.633 mg/g after 30 d, P<0.001). An interesting decrease in intestinal permeability, both of the small bowel and in the colon, was also recorded. The L/M ratio diminished from 0.021 in the active group to 0.014 and 0.015 after 30 and 45 days, respectively (P=0.045 and P=0.033 compared with placebo). The sucralose concentration decreased from 35.8 mg to 27.9 mg and 29.1 mg (P=0.038 and P=0.026 compared with placebo) at the end of the supplementation period and after the follow-up, respectively. No significant differences were recorded in the placebo after 30 days or at the end of the follow-up., Conclusions: The association of the EPSs produced by S. thermophilus ST10 and tara gum seems capable of significantly improving the intestinal functional barrier in healthy subjects. A wider study in subjects presenting impaired gut permeability would be useful in the future to confirm the positive results from this pilot trial. In any case, our findings are consistent with the parallel increase in exopolysaccharide concentration in the faecal material, thus suggesting the effective ability of the strain used to secrete EPSs in the gut lumen. An innovative approach of this type may be useful in helping to restore the physiological barrier by means of a merely natural and mechanical action.