Strenuous physical activity, sleep deprivation, and psychological stress are common features of military field training. This study aimed to evaluate the effects of supplementation with a synbiotic ice cream on salivary IgA, gastrointestinal symptoms, well-being indicators, and gut microbiota in young military participants undergoing field training. Sixty-five military completed the study: one group was supplemented for 30 days with synbiotic ice cream containing: 2.1x108 CFU/g for L. acidophilus LA-5 and 2.7x109 CFU/g for B. animalis BB-12 and 2.3g of inulin in the 60g of ice cream at manufacture, and the other with a placebo ice cream. Volunteers were evaluated at pre-supplementation (baseline), post-supplementation, and after a five-day military training. Bifidobacterium and Lactobacillus genera were measured in stool samples and both showed a higher differential abundance post-supplementation and training. Salivary IgA and gastrointestinal symptoms decreased at post-training in both groups (p<0.05; main effect of time); however, supplementation with synbiotic did not mitigate this effect. Tenseness and sleepiness were decreased in the synbiotic-treated group, but not in the placebo group at post-military training (p=0.01 and p=0.009, respectively; group x time effect). The other well-being indicators were not affected by the synbiotic supplementation. In conclusion, 30 days of synbiotic ice cream supplementation containing inulin, L. acidophilus LA-5, and B. animalis BB-12 favourably modulated gut microbiota and improved tenseness and sleepiness in healthy young military undergoing a 5-day field training. These improvements may be relevant to this population as they may influence the decision-making process in an environment of high physical and psychological stress.

The aim of this study was to evaluate the effect of symbiotic ice cream supplementation on immune response, mood and health parameters of military volutaries from the "Escola Preparatória de Cadetes" (Army Preparatory School) from Campinas during field training. This evaluation was done through the collection of saliva for the evaluation of IgA and through the application of questionnaires in three phases: after the washout period (t = 0), after supplementation in the period prior to field training (t = 1) and after field training (t = 2). It was possible to observe that after training there was a significant decrease in salivary IgA for both symbiotic and placebo group. In addition, the symbiotic group had significantly increased tranquility and reduced tension after training while the placebo group did not show changes in both states after training. These results demonstrate the importance of investigating the effects of probiotics associated with prebiotics on gut-brain axis.