Table 2.

Summary of the main features related to prebiotics, probiotics, and symbiotics.

Food Supplement	Mechanism of Action	Clinical Impact
Probiotics	Mainly bacteria able to reach the small intestine and the colon alive, providing positive interaction with gut microbiota of the host. Probiotics may exert various beneficial effects, including antimicrobial action, mucosal integrity, and enhancing the host immune response [100]	Uncertain clinical efficacy in CD patients. Kefir drink, a probiotic mix, improves abdominal pain, bloating, and inflammatory markers, along with increasing wellbeing sensation [110]
Prebiotics	Indigestible dietary compounds fueling beneficial bacteria of the gut microbiota	No major improvement of CD activity index, endoscopic score, or histopayhology [87,111]
Symbiotics	Combination of probiotics and prebiotics	A symbiotic containing Bifidobacterium longum and Synergy1 improved CD activity and histological scores [112]