Discussion
flatulence, anxiety, intestinal bloating, pain, fullness, gastrointestinal sensations, depression
SECONDARY
Metabolic profiles of urine samples across the 4 interventions were analyzed using unsupervised (PCA) methods to assess whether there were any intrinsic differences between samples collected pre and post intervention (PCA model: 7 principal components, RUrinary In this trial we explored the effects of the prebiotic OF and prebiotic candidate 2’FL, alone and in combination, on microbial composition, mood state (BDI, STAI Y1, STAI Y2, PANAS-SF), sleep quality, and CAR in healthy adults with mild-to-moderate levels of anxiety and depression. This is the first study to demonstrate that intake of OF and 2’FL can result in noticeable differences in microbial modulation and substantial improvements in mood, as reflected in BDI, STAI Y1, STAI Y2, PANAS-SF scores, and CAR in adults with mild-to-moderate levels of anxiety and depression.Large differences in microbial responses were seen between the 4 different interventions, with OF displaying the largest increases in microbial load in a number of different bacterial groups including It is well documented that large interindividual differences in responses exist in terms of bifidobacterial response to HMO supplementation, as the majority of adults do not possess the necessary bifidobacteria required to enzymatically degrade and utilize HMOs [One could speculate that increases in As previously stated, the majority of studies on the effects of prebiotics on cognitive function, mood state, and sleep quality failed to analyze changes in the gut microbiota [Several strains of bifidobacteria, We did not measure changes in SCFAs because fecal samples do not give an accurate measure of metabolite production within the colon, and we were unable to collect blood samples as a result of COVID-19 restrictions. The increases in several SCFA-producing bacteria (CAR values were significantly reduced across the OF, 2’FL, and OF/2’FL interventions, with OF showing the largest decreases. Our results are in accordance with those documented in probiotic interventions in healthy adults [In order to assess changes in stool frequency and stool consistency, the validated Bristol Stool Form Scale was used. In our cohort, significant increases in stool consistency were detected in the OF (both Similar changes in gastrointestinal sensations including flatulence, intestinal bloating, abdominal pressure, pain, and feeling of fullness were detected across the 4 interventions. Significant increases in flatulence and intestinal bloating upon consumption of OF have been documented previously [Finally, during the trial, volunteers were asked not to alter either their dietary intake or lifestyle, and dietary fiber intakes were estimated at 19.66 g/d at completion. These results are in line with the current UK average of 14.9 to 18 g/d and are significantly lower than the current UK recommendation of 30 g/d [We must acknowledge that one of the limitations of this study is that we chose not to measure SCFAs in feces as feces are not a good proxy for fermentation within the colon. It is still a commonly used reflective measure of levels of fermentation and could have potentially provided us with greater insights into differences in microbial responses between interventions and effects on microbial composition and mood state. Secondly, while care was taken in correcting for multiple comparisons, the testing of multiple secondary outcomes can result in the increased risk of generating and accepting type 1 errors. Lastly, while we found several significant correlations between bacterial taxa and improvements in mood state, we must acknowledge that correlation does not always equal causation, and due care must be taken in the interpretation of these findings.In conclusion, this is the first study to demonstrate that consumption of the prebiotic OF and prebiotic candidate 2’FL alone and in combination can result in substantial improvements in mood as reflected in BDI, STAI Y1 and Y2, and PANAS-SF scores and CAR. We can also conclude that OF induced substantial changes in microbial composition, especially increasing numbers of 