Consumption of Bifidobacterium animalis subsp. lactis BB-12 impacts upper respiratory tract infection and the function of NK and T cells in healthy adults

Scope Probiotics can modulate immunity and reduce upper respiratory tract infections (URTI) in humans; however few studies have examined both outcomes in the same trial. The goal of the current study was to investigate the effect of Bifidobacterium animalis subsp. lactis BB‐12, on natural killer (NK) and T‐cell function in conjunction with self‐reported cold/flu outcomes in healthy adults. Methods and results In a randomized, partially blinded, four‐period crossover study, healthy adults (n = 30) were recruited, and received four treatments for 4 weeks in a random order: (i) yogurt smoothies alone (YS); smoothies with BB‐12 added (ii) before (PRE) or (iii) after (POST) yogurt fermentation, or (iv) BB‐12 capsule (CAP). NK‐ and T‐cell function was assessed at baseline and after each treatment. Incidence and severity of cold/flu infection was quantified using self‐reported URTI questionnaires. Participants on YS, PRE, or CAP treatments had elevated IL‐2 secretion and NK‐cell cytotoxicity, concurrently with fewer days with URTI. However, the POST treatment did not change immune outcomes or the severity of URTI. Conclusion The timing of BB‐12 addition to yogurt smoothies in relation to the fermentation process influenced the impact of BB‐12 on immune function and cold/flu severity in young healthy adults. In a randomized, partially blinded, four‐period crossover study, we demonstrated that the timing of the addition of the probiotic Bifidobacterium animalis subsp. lactis BB‐12 to yogurt smoothies, in relation to the fermentation process, and its delivery matrix influenced the impact of BB‐12 on immune function (NK‐cell and T‐cell function) and cold/flu severity in young healthy adults.