TABLE 3.

Selected studies at a clinical level using prebiotics and/or their metabolites (SCFA) and probiotics to modulate brain physiology and function.

Prebiotics and/or Probiotics	Duration	Subjects	Outcome	References
FOS (5.5 g/day)	2 weeks	45 healthy male and female volunteers	Reduction in salivary cortisol levels Regulation of HPA axis to restore emotional perturbations	Schmidt et al. (2015)
GOS (5.5 g/day)
FOS (5 g/day)	4 weeks	79 irritable bowel syndrome (IBS) volunteers	Reduction in anxiety by modulating gut microbiota	Azpiroz et al. (2017)
GOS (7.5 g/day)	4 weeks	64 healthy female volunteers	Increased beneficial bacterial abundances Reduction in negative emotional bias and increase in positive bias associated with high anxious participants	Johnstone et al. (2021)
Mixture of GOS/FOS/pectic-derived acidic oligosaccharides (1.5 g/kg BW/day)	Gestation days (3–30)	77 preterm infants with a gestational age of less than 32 weeks	No improvement in the neurodevelopmental outcome was observed at the corrected age of 2 years	van den Berg et al. (2016)
Mixture of GOS/FOS and pectic-derived acidic oligosaccharides (80% + 20%)	Gestation days (3–30)	93 preterm infants with a gestational age of less than 32 weeks	No beneficial effect on neurodevelopmental outcome in preterm infants in the first year of life	LeCouffe et al. (2014)
Oligofructose-enriched inulin (5 g/day)	1 week	47 subjects	Selective improvement was observed with recall and recognition memory No effect on mood and sustained behavior was reported	Smith et al. (2015)
Probiotic mixture (5 g) of 2.7 × 107 CFU/g each of L. acidophilus T16, B. bifidum BIA-6, B. lactis BIA-7, and B. longum BIA-8	12 weeks	75 hemodialysis patients	Reduction in depression associated symptoms with a concomitant increase in serum BDNF levels in the synbiotic treated group	Haghighat et al. (2019)
Prebiotic mixture: 5 g each of FOS, GOS, and inulin
Synbiotic mixture: 15 g prebiotics and 5 g probiotics