Photo by http://benvandenbroecke.be/ Copyright, ISAPP 2019.
The scientific definition of the term ‘probiotic’ was proposed in a 2001 joint report of the Food and Agriculture Organization of the United Nations and the World Health Organization (FAO/WHO), and confirmed by an expert panel convened by ISAPP in 2013. The currently accepted definition of probiotics is: “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”
Live microorganisms may be present in many foods and supplements, but only characterized strains with a scientifically demonstrated effect on health may be correctly called probiotics. Bacteria present in traditional fermented foods and beverages such as kombucha, sauerkraut, and kimchi are not considered probiotics, since their health effects have not been studied and they are uncharacterized.
Probiotics are known by genus, species, and strain: for example, Lactobacillus acidophilus ABC. The strain designation is important, as different strains of even the same species may have different health effects. Dose also matters: a probiotic consumed at a higher dose may not necessarily have a greater health benefit than one consumed at a lower dose.
Probiotic products (usually dietary supplements or foods) may be recommended for different conditions or symptoms an individual is experiencing. Decades of study on various probiotic strains have revealed particular health benefits – however, remember that not all these benefits will be delivered by any one product:
- Helping reduce antibiotic-associated diarrhea
- Helping manage digestive symptoms (including in irritable bowel syndrome)
- Helping reduce colic symptoms and eczema in infants
- Helping reduce symptoms of lactose maldigestion
- Treating acute pediatric infectious diarrhea
- Decreasing the risk or duration of common infections, such as infections of the upper respiratory tract infections or gut
An increasing number of studies also support probiotic health benefits beyond the digestive tract: for oral health in children, and for liver health, bacterial vaginosis, and other indications.
A good safety profile has been documented in clinical trials for many probiotic strains; caution may be advisable in certain populations: immunocompromised individuals, those with a serious illness, those with ‘short gut’, and young infants.
In some cases, probiotic mechanisms of action are known; in other cases, they are not known even though a health benefit has been demonstrated. A common misconception is that probiotics need to alter the gut microbiota in order to be effective. In fact, probiotics rarely take up permanent residence in the gut microbiota but may act through a number of alternative mechanisms.