Probiotics are live microorganisms, including the following bacterial strains;
- Lactobacillus acidophilus,
- Lactobacillus rhamnosus, and
- Bifidobacterium longum
- and the yeast Saccharomyces boulardii.
When taken daily for several weeks, these organisms can increase the number of beneficial bacteria in the gut. This in turn can result in a health benefit for the host. There is a good amount of research to show that there can be a reduction in the incidence of URTI by up to 50%, and a shortening of the duration of sickness by 2 days, when taking probiotics. Probiotics might also help reduce inflammation.
There are several ways immune function may be improved by probiotics, including enhancing gut barrier function, increasing immunoglobulin production, inhibiting viral replication, and enhancing the phagocytic activity of white blood cells. Mechanisms of effects are still unclear, and each bacterium may have a differing mechanism.
Probiotics are very safe to use, as they have a long history of use in food and are often present in the normal gastrointestinal microbiota of humans. Probiotics are naturally occurring in many foods like yogurt, pickles, sourdough bread, as well as in fermented foods like kefir, kombucha, sauerkraut and kimchi. They are also added to some food products and are available as dietary supplements in tablet form.