The role of fermented foods in gut health
Enhancing human health is an evolving strategy, and one intriguing aspect is the modulation of the microbiome by consuming fermented foods as part of a healthy diet. However, understanding the mechanisms underlying the dos and don’ts of a particular food is essential for making informed health decisions.
Fermented foods are defined as those made through desired microbial growth and enzymatic conversions of food components. During fermentation, microorganisms transform raw materials, altering the nutritional composition and bioactive properties of foods. This process not only provides a unique taste and prolongs shelf life, but also enriches food with nutrients and live microbes that may offer several health benefits such as improved digestion, enhanced immune function, and increased nutrient absorption. It’s essential to note that only fermented foods containing specific live microbial strains with defined health benefits are considered probiotic foods.
Unfortunately, the increasing industrialization of food has led to a reduced diversity of fermented foods, contributing to a decline in the gut microbiome diversity. The diversity of microorganisms in the gut is important for overall well-being, and influences gut health, immune function, metabolism, and perhaps even brain health. Recognizing this loss of diversity, coupled with an increase in inflammatory markers in urbanized regions, has renewed the interest in understanding the mechanisms behind the positive and negative effects of fermented foods. Recently, nutritional scientists have reviewed evidence linking fermented foods to their health benefits and potential drawbacks.
Some fermented foods provide health benefits supported by science
Science has revealed some of the mechanisms behind the positive effects of consuming fermented foods containing microorganisms and bioactive compounds on gastrointestinal health.
- Pathogen protection: antimicrobial compounds called bacteriocins, produced during food fermentation, not only inhibit the growth of harmful bacteria situated in the gut of animals and humans, but also enhance the integrity of the intestinal barrier, reducing the risk of infection and inflammation.
- Short-Chain Fatty Acids (SCFAs) production: derived from dietary fiber fermentation, SCFAs provide energy to colon cells and may help in regulating immune function, reducing inflammation, and promoting gut health as shown in mouse models.
- Vitamin K Boost: fermented foods with increased vitamin K concentration may contribute to systemic and gut health by suppressing colonic tumor development, improving intestinal integrity, and inhibiting gut pathogens as studied in animal models.
Additional benefits can also arise from the removal of substances with limited tolerance or absorption for some individuals, such as:
- Lactose: fermented dairy products like yogurts and aged cheeses have undetectable or reduced lactose content, making them suitable for those with lactose intolerance. Recently, yogurts have received a qualified health claim recognizing their association with a reduced risk of type 2 diabetes, according to limited scientific evidence.
- FODMAPs: fermentation decreases fermentable carbohydrates, reducing digestive discomfort in some individuals. By leaving the dough to ferment with complex microbial communities or a specific strain such as Saccharomyces cerevisiae, the carbohydrate content can be reduced by 40-80% compared to unfermented flour.
- Phytic Acid: phytate traps some dietary minerals (iron, zinc and calcium) and fermentation reduces the content of phytic acid, thereby improving the absorption of minerals.
What you need to consider before incorporating fermented foods into your diet
Incorporating fermented foods into our diet not only brings specific health benefits but also safely exposes us to microorganisms, enhancing the diversity of our gut microbiome. Additionally, postbiotics, defined as preparations of inanimate microorganisms and/or their components resulting from fermentation, may confer health benefits to the host, and can provide complementary benefits. Postbiotics, found in yogurt and dietary supplements, may ease digestion and prevent infections without the safety concerns of live microbes.
However, it is important to acknowledge that, beyond the potential for clinical benefit from fermented foods in certain circumstances, the design of specific interventions requires further evidence to define the optimum dose and safety for specific gastrointestinal conditions. For example, despite its health benefits, the popular fermented drink kombucha cannot be recommended for children, pregnant women, newborns, and individuals with liver-associated diseases owing to its undefined alcoholic content.
While the application of fermented foods to clinical practice is in its infancy, incorporating high-fermented foods into your diet can improve your gut microbiota diversity and decrease your inflammatory state.
With this in mind, you can combine fermented foods with prebiotic-rich foods, such as fruits or seeds, obtaining enhanced effects for your health and your general wellbeing. In your daily menu, for instance, you can incorporate milk-derived fermented foods, sourdough bread with fruits or seeds to your breakfast and desserts, instead of consuming sweet and salty foods.
References:
Mukherjee, A., Breselge, S., Dimidi, E. et al. Fermented foods and gastrointestinal health: underlying mechanisms. Nat Rev Gastroenterol Hepatol.2023. doi:10.1038/s41575-023-00869-x
Valentino, V., Magliulo, R., Farsi, D. et al. Fermented foods, their microbiome and its potential in boosting human health. Microb Biotechnol. 2024.17(2):e14428. doi: 10.1111/1751-7915.14428.
Gibson, G., Hutkins, R., Sanders, M. et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nat Rev Gastroenterol Hepatol. 2017.14: 491–502. doi:10.1038/nrgastro.2017.75
Hill, C., Guarner, F., Reid, G. et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev G
Marco, M.L., Sanders, M.E., Gänzle, M. et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nat Rev Gastroenterol Hepatol. 2021.18: 196–208.doi:10.1038/s41575-020-00390-5
EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on the substantiation of health claims related to live yoghurt cultures and improved lactose digestion (ID 1143, 2976) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA J. 2010.8(10): 1763.
Bali, V., Panesar, P.S., Bera, M.B., Kennedy, J.F. Bacteriocins: recent trends and potential applications. Crit Rev Food Sci Nutr. 2016.56: 817–834. doi: 10.1080/10408398.2013.764486.
Staudacher, H.M. Fermented foods: fad or favourable addition to the diet? Lancet Gastroenterol Hepatol. 2023.4(1): 19.
de Miranda J.F., Ruiz L.F., Silva C.B., Uekane T.M., Silva K.A., Gonzalez A.G.M., Fernandes F.F., Lima A.R. Kombucha: A review of substrates, regulations, composition, and biological properties. J Food Sci. 2022 Feb;87(2): 503-527. doi: 10.1111/1750-3841.16029.
Wastyk, H.C., et al. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021.184(16): 4137-4153.e14.astroenterol Hepatol. 2014.66(11): 506–514 (2014). doi: 10.1038/nrgastro.2014.66