Probiotic

Probiotics are live microorganisms in foods intended to improve or restore microbiota in the gut.^[1][2] Probiotic products include yogurt, cheese, some fermented foods, such as sourdough bread and nattō, dietary supplements, and clinical capsules containing a specific probiotic strain.

Probiotics are considered generally safe to consume, but may cause bacteria–host interactions and unwanted side effects in some cases.^[3][4][5][6] Many claimed health benefits, such as treating eczema or curing vaginal infections, lack substantial scientific support.^[1][7]

The first discovered probiotic was a certain strain of bacillus in Bulgarian yoghurt, called Lactobacillus bulgaricus. The discovery was made in 1905 by Bulgarian physician and microbiologist Stamen Grigorov. The modern-day theory is generally attributed to Russian Nobel Prize laureate Élie Metchnikoff, who postulated around 1907 that yoghurt-consuming Bulgarian peasants lived longer.^[8]

A growing probiotics market has led to the need for stricter requirements for scientific substantiation of putative benefits conferred by microorganisms claimed to be probiotic.^[9] Although some evidence claimed benefits are marketed towards using probiotic, such as reducing gastrointestinal discomfort, improving immune health,^[10] relieving constipation, or avoiding the common cold, such claims are strain-specific and cannot be extrapolated to other strains.^[9][11][12] As of 2019, numerous applications for approval of health claims by European manufacturers of probiotic dietary supplements have been rejected by the European Food Safety Authority for insufficient evidence of beneficial mechanism or efficacy.^[10][13]