The use of synbiotics as health promoters is still poorly defined, and human intervention studies are scarce. This study was designed to evaluate the effects of a commercialized synbiotic product containing Lactobacillus acidophilus La5, Bifidobacterium animalis ssp. lactis Bb-12, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus paracasei ssp. paracasei, Streptococcus thermophilus, and fructooligosaccharides on the self-reported gastrointestinal well-being and the immunoinflammatory status of healthy human subjects. In this randomized, double-blind, placebo-controlled study, 20 women and 16 men (25-45 years old) received either three tablets per day of the synbiotic product (2.4 × 10(9) colony-forming units/day) or placebo during 6 weeks. Gastrointestinal symptoms and bowel habits were evaluated through a self-administered questionnaire. In those subjects suffering from any kind of digestive disturbance (mild dyspepsia, flatulence, postprandial bloating, constipation, etc.), improvements in symptoms after product consumption were also evaluated. Blood lymphocyte subsets, phagocytic activity, serum C-reactive protein, ceruloplasmin, and adhesion molecules concentrations were analyzed prior and after treatment. A significant improvement in overall self-reported gastrointestinal symptoms and bowel habit was found in the synbiotic group. A marginal effect of treatment (analysis of variance P = .050) was observed with L-selectin, which showed a significant decrease in the synbiotic group (P = .019). In addition, basal L-selectin levels correlated with final intercellular adhesion molecule (ICAM)-1 levels (r = 0.468; P = .050), and basal ICAM-1 levels tended to correlate negatively with final L-selectin concentration (r = -0.457; P = .056). None of these correlations was found in the placebo group. The rest of the immunological parameters studied were not modified by the intervention. In conclusion, consumption of the synbiotic product improves self-perceived bowel habits and might facilitate a better profile of adhesion molecules in healthy adults.