Nowadays there is an increased interest in gut health and immunity. Research on the gut microbiome has encouraged further attention to the study of probiotics and prebiotics, which are essential dietary components to the intestinal and overall health. Probiotics are live microorganisms found in food such as yogurt and fermented vegetables. The most studied probiotics are Lactobacilli and Bifidobacteria. Their consumption fosters a healthy immune system and reduces damaging inflammation in the body. On the other hand, prebiotics are nondigestible food ingredients that nurture our microorganisms living in the gut (microbiome). The most common prebiotics are fibre such as oligofructose, inulin, galacto-oligosaccharides, lactulose and breast milk oligosaccharides. As a result, to maintain a healthy gut, it is essential to feed the microbiome with prebiotics. A traditional western diet, based on the consumption of heavy fat and meat doesn’t allow microorganisms to prosper in the gut, causing a toxic environment. On the other hand, a healthy diet based on the consumption of fruit and vegetables, will allow your gut to stay healthy. The recommended dose of prebiotics is 4 g/day. It is not advised to consume more than 20g/day.
What is the mechanism of action?
The mechanism of action of both probiotics and prebiotics is complex and not completely defined. Probiotics interact with both the host and the microbiome by 4 mechanisms:
Protection of the host through the production of antimicrobial substances.
Adhesion to the epithelial cells to block the pathogens.
Immunomodulation of the host.
Inhibition of bacterial toxins production.
Overall, probiotics protect us against the entrance of pathogenic microorganisms and they help us to maintain a balance with the beneficial bacteria in the microbiome. On the other hand, prebiotics interact directly with the host by producing short-chain fatty acids (SCFA) (acetate, propionate, butyrate, lactate) that stimulate the growth and activity of the beneficial bacteria in the gastrointestinal tract, enhancing the bioavailability and uptake of vitamins and minerals.
Clinical application:
Clinical studies have shown that probiotics help to counteract lactose maldigestion, as lactic acid bacteria (found in yogurt as an example), contain high levels of lactase which breaks down lactose into smaller sugars (glucose and galactose), thus relieving maldigestion symptoms. Probiotics are also used to combat diarrhoea. Diarrhoea is the result of an imbalance of bacteria in the gut, dysbiosis. Probiotics are able to restore the balance, thereby promoting a normal bowel function and shortening the duration of diarrhoea. There is also evidence that probiotics counteract CRC (colorectal cancer). CRC is usually caused by your diet and its interaction with the gut flora together with the reduced protection from the ageing microbiota. Due to CRC, gut bacteria convert dietary compounds into toxic enzymes. Probiotics are able to reduce the levels of these enzymes, providing protection to the colon. Finally, probiotics are recommended for different types of digestive complaints, particularly against IBS (irritable bowel syndrome). Probiotics counteract IBS by restoring the number of beneficial bacteria in the gut that are depleted due to the disease. On the other hand, prebiotics have been suggested to modify triglyceride levels and cholesterol, thereby reducing the risk of hypercholesterolaemia and also reduce the risk of colon cancer by inhibiting the activity of microbial enzymes involved in the production of toxins.
Food sources:
The best food sources that contain live bacteria are yogurt, cheese, kefir, kimchi, kombucha and sauerkraut. You can also use probiotic supplements. Remember that microorganisms are killed with the heat. Therefore, do not cook the food or take a supplement with hot water. Best prebiotic sources are oats, beans, garlic, banana, onions and asparagus.
Curiosity:
Do you know that probiotics are also used to increase the health of plants and animals? Specific bacterial strains such as the Bacillus bacteria, can be used to protect plants against diseases, pests and nematodes. At the same time, probiotics improve digestibility and feed efficiency in animals.
References:
Varzakas, T., Kandylis, P., Dimitrellou, D., Salamoura, C., Zakynthinos, G., Proestos, C (2018). Innovative and fortified food: probiotics, prebiotics, GMOs, and superfood. Food Science, Technology and Nutrition, pp. 67-129.
Guarino M P L., Altomare, A., Emerenziani, S., Di Rosa, C., Ribolsi, M., Balestrieri, P., Iovino, P., Rocchi, G., Cicala, M (2020). Mechanism of action of prebiotics and their effects on gastro-intestinal disorders in adults. Nutrients, 12(4).
Sanders, M E., Merenstein, D J., Reid, G., Gibson, G R., Rastall, R (2019). Probiotics and prebiotics in intestinal health and disease: from biology to the clinic, vol.6 pp. 605-616.
Markowiak, P., Slizewska, K (2017). Effects of probiotics, prebiotics, and synbiotics in human health, Nutrients, 9(9).
Cunningham, M., Peril, A., Barnard, A., Benoit, V., Grimaldi, R., Guyonnet, D., Holsher, H., Hunter, K., Manurung, S., Obis, D., Petrova, M., Steinert, R., Swanson, K., Sinderen, D., Vulevic, J., Gibson, G (2021). Shaping the future of probiotics and prebiotics. Trends in Microbiology.
Tuohy K., Probert, H., Smejkal, C., Gibson, G (2003). Using probiotics and prebiotics to improve gut health. Drug Discovery Today, 15 pp. 692-700.
Harvard Health Publishing (2021). Nourish the healthy bacteria in your digestive tract with a mix of probiotics and prebiotics. [Assessed online] https://www.health.harvard.edu/staying-healthy/feed-your-gut
World gastroenterology organisation global guidelines (2011). Probiotics and prebiotics. [Assessed online] https://www.spg.pt/wp-content/uploads/2015/11/2011-Probiotics_FINAL_20110116.pdf