New global guidelines on identifying and using probiotics and prebiotics have been drawn up in recognition of their potential benefits in supporting gut health (1).
The guidelines, published by the World Gastroenterology Organisation, reflect the growing evidence for the efficacy of specific probiotic strains or prebiotics in a variety of gastrointestinal conditions. Developed by a worldwide team of gastroenterology experts, they represent a shift in the way health professionals view these popular food ingredients.
How do we define probiotics?
Over a century ago, scientists proposed that lactic acid bacteria – commonly used for food fermentation, e.g. such as for the fermentation of milk in yogurt by the strains Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus – can provide health benefits to consumers by modifying their gut microbiota. Today, over 1,500 clinical trials have studied the effects of numerous strains of potentially probiotic bacteria on various human health outcomes. But how do we know which strains of bacteria are probiotic?
According to the World Gastroenterology Organisation, probiotics are defined as live microorganisms that confer a health benefit to humans when consumed in adequate amounts (2). Common probiotics include several strains of Lactobacillus and Bifidobacterium lactic acid bacteria, along with some strains of other bacteria and yeasts. In general, the term “probiotic” should be reserved for live microbial strains that have demonstrated health benefits in controlled human studies.
For more information on the health benefits of probiotics, see Scientists unravel the healthy secrets of probiotics.
How do we define prebiotics?
The concept of prebiotics – compounds that are not digested by humans but lead to health benefits by influencing the gut microbiome – is more recent (3,4). Most prebiotics are either used as food ingredients or found naturally in many foods – common examples include lactulose and oligofructose.
The World Gastroenterology Organisation defines prebiotics as selectively fermented ingredients that result in specific changes to the composition and/or activity of gut microbiota, conferring health benefits. However, the extent to which we may experience these benefits varies due to several factors, including an individual’s gut microbiota and diet.
How do probiotics and prebiotics work?
The consumption of prebiotics or probiotics is intended to influence the gut environment, which is inhabited by trillions of microbes, for the benefit of human health.
Prebiotics affect intestinal bacteria by enhancing the numbers or activities of beneficial bacteria. This may result in decreasing the population of potentially pathogenic microorganisms or reducing potentially deleterious metabolic activities of host microbiota. Prebiotics may also have an impact on immune function.
Probiotic strains may mediate health effects through one or more of several mechanisms:
- Probiotic strains can lead to immune benefits by activating local macrophages, modulating cytokine profiles, and raising tolerance to food antigens.
- Probiotics can also lead to improved gut health and reduced inflammation though mechanisms including food digestion, altered acidity, pathogen inhibition, and intestinal barrier enhancement.
What are the potential health benefits of probiotics or prebiotics?
Both probiotics and prebiotics have been shown to have beneficial effects on gut health. Their effects are strain- and dose-specific for probiotics and based on a particular formulation for prebiotics. Based on current evidence, the World Gastroenterology Organisation has summarized several potential health benefits:
- Diarrhoea treatment and prevention – some probiotic strains can reduce the severity and duration of acute infectious diarrhoea in children, as well as preventing of adult and childhood diarrhoea in certain settings (5).
- Immune response – several probiotic strains and the prebiotic oligofructose are useful in improving the immune response to infectious diseases.
- Lactose malabsorption – Probiotic strains of Streptococcus and Lactobacillus – commonly found in yogurt – improve lactose digestion and reduce symptoms related to lactose intolerance (6).
- Irritable bowel syndrome (IBS) – some strains of probiotics may alleviate symptoms and provide pain relief from IBS.
- Inflammatory bowel disease – certain probiotics may be effective in preventing pouchitis, inflammation in the lining of a pouch created during surgery to treat treatment of some ulcerative colitis (7).
- Non-alcoholic fatty liver disease (NAFLD) – certain probiotics can improve markers of liver function in adults and children with NAFLD.
- Hepatic encephalopathy prevention and treatment – prebiotics such as lactulose are commonly used for the prevention and treatment of hepatic encephalopathy (8).
Probiotics and prebiotics have also been shown to have effects beyond gut health, including allergy prevention and benefits for skin, dental, and respiratory health.
So, what does this mean for clinical practice?
Probiotic- and prebiotic-containing products are available in many forms, most commonly as foods or supplements. Recommendations for probiotic and prebiotic use should tie specific strains or formulations to potential health benefits based on clinical studies.
Different probiotics strains have unique properties that may account for their particular health benefits. However, scientists are increasingly recognising that some mechanisms of probiotic activity may be shared among strains.
“‘The administration or use of prebiotics or probiotics is intended to influence the gut environment, which is inhabited by trillions of microbes, for the benefit of human health. Both probiotics and prebiotics have been shown to have beneficial effects that extend beyond the gut.’”
