Immune status, well-being and gut microbiota in military supplemented with synbiotic ice cream and submitted to field training: a randomised clinical trial.

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.