Probiotics affect the digestive-tract ecosystem in three ways:
1. Probiotics change the way in which the gut lining reacts to inflammation
Probiotics help to activate white blood cells called macrophages, which use the process of phagocytosis to engulf foreign particles and digest them.
Once these particles have been digested, our B cells (another type of white blood cell) produce antibodies against the foreign body, while immunoglobulin A (IgA – a type of antibody) is released into the digestive tract.
IgA is the first line of defence against ingested pathogens.
The above mechanisms all help to prevent infection of the gut lining.
2. Probiotics interact with other species of bacteria that inhabit the gut
These species include pathogenic substances and/or harmful bacteria.
Probiotics are able to:
- Digest food and compete for nutrients with pathogens. If healthy bacteria predominate in the gut, the pathogens will be left without “fuel” and will be more likely to die. To put it differently, the probiotics create a competitive environment in which the harmful bacteria struggle to survive.
- Change the pH in the gut to a less favourable pH for pathogens – again making it harder for the harmful bacteria to survive.
- Produce a substance called bacteriocin, which stops the growth of similar or closely related bacterial strain(s). In this way, probiotics also inhibit the growth of pathogens.
- Change the way in which pathogens produce toxins.
These benefits all enhance your digestive tract’s ability to fight pathogens and infection of the gut lining.
3. Probiotics generate short-chain fatty acids (SCFAs)
SCFAs are receiving a lot of attention in gut-related research, as they’ve been shown to exert multiple beneficial effects.
Research shows that they:
- Are a key energy source for the cells lining your colon. In this way, they keep the colon in good working condition.
- Have been linked to the prevention of colon cancer.
Reviewed by Kim Hofmann, registered dietitian, BSc Medical (Honours) Nutrition and Dietetics, BSc (Honours) Psychology. April 2018.