synbiotic

A synbiotic is a product or concept that combines a live microorganism with a substrate that is selectively utilized by host microorganisms, intended to confer a synergistic health benefit by modulating the gut microbiota. The term was introduced in 1995 by Gibson and Rastall to describe the intentional pairing of probiotics and prebiotics to enhance colonization and metabolic activity.

The idea is that the prebiotic component serves as targeted fuel for the probiotic strain and for resident beneficial microbes, improving survival, colonization, and functional output such as short-chain fatty acid production. This synergy aims to produce greater benefits than either component alone.

Common probiotic organisms used in synbiotics include Lactobacillus and Bifidobacterium species, while prebiotic substrates include inulin, fructooligosaccharides, galactooligosaccharides, and resistant starch. Some products also use non-bacterial probiotics such as Saccharomyces boulardii.

Evidence from clinical trials is mixed and depends on the specific combination, dose, and population. Some studies report reduced antibiotic-associated diarrhea, improvements in irritable bowel syndrome symptoms, or modest metabolic benefits, but results are inconsistent.

Safety considerations mirror those of probiotics and prebiotics. Synbiotics are generally safe for healthy individuals, but there is a theoretical risk of infection in immunocompromised people or those with severe illness, and product quality and viability are important factors.

Regulatory guidance on synbiotics varies by region, with definitions and labeling standards often linked to probiotic and prebiotic products. Ongoing research aims to identify effective strain–substrate combinations and clarify mechanisms of action.