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Human and Clinical Nutrition
Abbreviations: B. bifidum, Bifidobacterium bifidum R0071; B. infantis, Bifidobacterium longum ssp. infantis R0033; GOS, galacto-oligosaccharides; L. helveticus, Lactobacillus helveticus R0052; SI, symptom intensity; sIgA, secretory IgA
Acute psychological stress in students during academic exams is associated with decreased cellular immunity and increased intensity of cold/flu symptoms and percentage of days with a cold/flu(1,2). Supplementation with the prebiotic galacto-oligosaccharides (GOS) resulted in lower cold/flu symptom intensity (SI) scores and a reduction in the percentage of days with a cold/flu in university students undergoing academic stress(1). Selective fermentation of GOS resulting in increased numbers of bifidobacteria and enhanced cell-mediated immunity has been proposed as the mechanism by which this prebiotic modulated immune health(3,4). GOS produces a highly specific bifidogenic response and has not been observed in all individuals who consume this probiotic(5). Thus, directly providing bifidobacteria in the form of a probiotic supplement may have a bigger impact on the immune health of a population.
A recent systematic review and meta-analysis has confirmed that probiotics belonging to the genera Bifidobacterium, as well as Lactobacillus, are effective in reducing the duration of episodes of acute respiratory illness by almost a day compared with placebo in healthy children and adults(6). None of the studies included in the meta-analysis has examined the effect of these probiotics on cold/flu in students during academic exams, a classic model for acute psychological stress(7). A single study that has examined the effect of the combination of Lactobacillus rhamnosus LGG and Bifidobacterium animalis ssp. lactis BB-12 on the duration of cold/flu in college students over a 12-week period of their spring semester was included in the meta-analysis(8). An episode of cold/flu was defined as an affirmative answer on two consecutive days to a question asking whether the student felt sick today. The duration of the self-reported cold/flu was approximately 2 d shorter, and the associated symptoms were less severe with the probiotic compared with placebo. The authors suggested that the multi-species probiotic may have attenuated the...