What happens in the gut, and more specifically within the intestinal microbiota, has different impacts on overall health. Let's take a look at its role in the immune system!
What is the immune system and what does it do?
The immune system protects the body against infection and other aggressions (4). It includes physical barriers (e.g. skin, mucous membranes of the gastrointestinal and respiratory tracts) and biochemical barriers (e.g. secretions, mucus, gastric acid), many different immune cells (e.g. granulocytes, B and T lymphocytes) and antibodies (e.g. immunoglobulins) (4).
What are the links between the intestinal microbiota and the immune system?
Did you know that 70 % of the body's immune cells are found in the intestine? (1, 4)?
That's right, the microbiota plays several essential roles in immunity (1, 4).
- It acts as the first line of defense against pathogenic (harmful) agents (1, 4, 8). Good« bacteria form the intestinal barrier, preventing pathogenic bacteria from establishing themselves in the intestine (1, 4, 8). The presence of a mucus layer helps limit the growth of harmful bacteria and substances (1, 2, 4, 8).
- It helps «educate» and activate immune cells, distinguishing between beneficial and harmful elements (1, 4, 8).
- It helps modulate inflammation (1). Indeed, the presence of dysbiosis (imbalance of intestinal bacteria) weakens immunity and promotes inflammatory processes in the body (1).
- It synthesizes immune-enhancing substances such as antimicrobial molecules (bacteriocins) that can kill harmful bacteria (3). The microbiota also promotes the production of short-chain fatty acids (AGCC), playing a role in the body's immune response (1, 3, 5).
How to improve microbiota health to support immunity?
Since the microbiota is influenced by the’power supply and lifestyle habits, However, certain nutritional recommendations can help promote digestive health and immunity.
The term «boosting the immune system» is often controversial. In fact, we don't want to boost the immune system, because we don't want it to work harder than it's supposed to. Rather, we want to give it every opportunity to work well. And when it comes to nutrition, certain nutrients are key:
- A a diet rich in dietary fibre and prebiotics help preserve a healthy intestinal barrier and optimal mucus layer, mitigating pathogenic infections (2, 7)
- Conversely: a low-fiber diet encourages the proliferation and activity of mucus-degrading bacteria (2)
- So less fibre = thinner mucus layer = less effective intestinal barrier against pathogens!
- The synthesis of AGCC (lexicon link, https://epithelia.ca/lexique-de-la-sante-intestinale/) by the fermentation of these foods also contributes to the body's immune response, among other things through the production and secretion of intestinal mucus (7).
- Conversely: a low-fiber diet encourages the proliferation and activity of mucus-degrading bacteria (2)
In short, a healthy gut microbiota maintains a symbiotic relationship within the intestinal mucosa, providing essential functions in metabolism, immunity and host protection (7).
In this way, we focus on all the foods that promote a balanced intestinal microbiota and reduce those that harm it (7).
We aim at (6, 7):
↑ consumption of :
Omega-3 fatty fish (salmon, trout, tuna, sardines, mackerel, herring), flax/chia/hemp/camel seeds, walnuts, pumpkin/sunflower seeds
Dietary fiber vegetables, fruits, whole grains (whole wheat, oats, quinoa, hulled barley, buckwheat, brown rice), nuts, seeds, legumes (chickpeas, lentils, beans), edamame
Plant proteins legumes (chickpeas, lentils, beans), tofu, edamame, textured vegetable protein (TVP), tempeh, nuts, seeds
↓ consumption of :
Saturated fatty acids red meats (beef, pork, veal, lamb), cold cuts, palm oil, lard, shortening
Foods rich in added sugars candy, desserts (cake, doughnuts, cookies, pastries), chocolate, ice cream, soft drinks, fruit cocktails
Foods with food additives and sweeteners (e.g. carboxymethylcellulose, polysorbate 80, aspartame, sucralose, saccharin): sweets, desserts, cakes, cookies, ready meals, sauces, salad dressings, ice cream, low-fat or sugar-free products such as soft drinks, flavored waters, sports drinks.
In short, aim for a balanced diet rich in vegetables and fruit is good for immunity. A diversified diet based on the’Mediterranean diet helps to restore all key nutrients and promote a greater diversity of intestinal bacteria (6).
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References
- Cristofori et al (2021) Anti-Inflammatory and Immunomodulatory Effects of Probiotics in Gut Inflammation: A Door to the Body. Front Immunol Feb 26;12:578386. https://pubmed.ncbi.nlm.nih.gov/33717063/
- Desai et al (2016) A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility. Cell Nov 17;167(5):1339-1353.e21. https://pubmed.ncbi.nlm.nih.gov/27863247/
- Canadian Digestive Health Foundation (2023) How diet can support gut health and the immune system, online, https://cdhf.ca/fr/comment-lalimentation-peut-elle-favoriser-la-sante-intestinale-et-le-systeme-immunitaire/
- Maggini et al (2018) Immune Function and Micronutrient Requirements Change over the Life Course. Nutrients Oct 17;10(10):1531. https://pubmed.ncbi.nlm.nih.gov/30336639/
- Mazziotta et al (2023) Probiotics Mechanism of Action on Immune Cells and Beneficial Effects on Human Health Cells Jan 2;12(1):184. https://pubmed.ncbi.nlm.nih.gov/36611977/
- Rinninella et al (2023) The role of diet in shaping human gut microbiota. Best Pract Res Clin Gastroenterol Feb-Mar;62-63:101828. https://pubmed.ncbi.nlm.nih.gov/37094913/
- Statovci et al (2017) The Impact of Western Diet and Nutrients on the Microbiota and Immune Response at Mucosal Interfaces. Front Immunol Jul 28;8:838. https://pubmed.ncbi.nlm.nih.gov/28804483/
- Yan and Polk (2011) Probiotics and immune health. Curr Opin Gastroenterol Oct;27(6):496-501. https://pubmed.ncbi.nlm.nih.gov/21897224/
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