Modifications in gastrointestinal parameters, intestinal colonization and tolerance are some of the main goals claimed for probiotics. However, although healthy people are the common target for these new functional food products, the number of clinical trials analysing the effects of probiotics in gastrointestinal parameters of healthy subjects is very scarce. A randomized, double blind, placebo-controlled human clinical trial involving 30 healthy adults was performed to investigate the effect of a fermented product containing two probiotic strains, Lactobacillus gasseri CECT5714 and Lactobacillus coryniformis CECT5711, on several blood and fecal parameters, most of them related to the host intestinal function. The volunteers were randomly distributed into two groups, one receiving a standard yogurt and the other a similar dairy fermented product in which the Lactobacillus delbreuckii subsp. bulgaricus yogurt strain had been replaced by a combination of the probiotic strains L. gasseri CECT5714 and L. coryniformis CECT5711. The volunteers that received the probiotic strains reported no adverse effects and the strains could be isolated from their feces at a relatively high level. In fact, the concentration of fecal lactic acid bacteria significantly increased in the probiotic group. Additionally, the oral administration of the probiotic strains led to an improvement of parameters such as the production of short chain fatty acids, the fecal moisture and the frequency and volume of the stools. As a result, the volunteers assigned to the probiotic group perceived a clear improvement in their intestinal habits. The study revealed that probiotics may exert a positive effect on healthy adults.