Table 1.

Potential effect of oligosaccharides in reducing post-COVID-19 syndromes and their related mechanisms.

Oligosaccharides	Methods	Results and Mechanisms	Ref.
Arabinoxylan–oligosaccharides	20 healthy volunteers consumed arabinoxylan–oligosaccharides (15 g/d in the first week, 30 g/d in the second week)	There has been an increase in colonic fermentation, resulting in a higher concentration of stool moisture.	[32]
Dragon fruit oligosaccharides	107 healthy adults, divided into 3 groups that received oligosaccharides in drinking waterdoses of 4 and 8 g/day, compared to the placebo group for 4 weeks	Enhancing IgA levels, promoting a healthy gut microbiota, and reducing harmful bacteria.	[33]
Fructo-oligosaccharides	56 people aged 18–75 years with spinal cord injury during inpatient rehabilitation, who require antibiotics, will be given probiotics or placebo randomly	Decreased occurrences of nausea and diarrhea, leading to an improved quality of life.	[34]
Fructo-oligosaccharides	50 patients with type-2 diabetes were randomly assigned to the symbiotic or placebo groups to receive one sachet daily for 12 weeks	There were no changes observed in the levels of serum triglycerides, total cholesterol, HDL-cholesterol, and LDL-cholesterol. However, there was an improvement in metabolic factors and a reduction in inflammation.	[35]
Fructo-oligosaccharides	Placebo-controlled, randomized, double blind design in 60 older participants aged 65 and over	There was improvement observed in two frailty criteria, specifically exhaustion and handgrip strength.	[36]
Fructo-oligosaccharides	27 middle-aged subjects were randomized to take synbiotic (Bifidobacterium animalis lactis and oligosaccharides) or placebo for 30 days	There was a reduction in inflammatory markers along with an improvement in gut disorders.	[37]
Galacto- oligosaccharides	Double-blind, placebo-controlled, crossover study, subjects from the general population	The intervention resulted in improvements in bloating, flatulence, and abdominal pain. It exhibited high selectivity towards bifidobacteria, while also modulating the metabolic and compositional aspects of the microbiota.	[38,39,40]
Xylo-oligosaccharides	Prebiotic (xylo-oligosaccharide, 8 g/d), probiotic (Bifidobacterium animalis) or synbiotic was given to healthy adults (25–65 years) for 21 days	The intervention promoted bifidogenesis, resulting in an increase in bifidobacteria population. It also improved aspects of the plasma lipid profile, and effectively modulated markers of immune function in healthy adults.	[41]