When it comes to supporting our immune system, it all begins with the gut.  Up to 80% of our immune system resides within the gut. Supporting your gut means you’re supporting your ability to fight off viruses and other pathogens. Find out all the practical ways you can enhance your immunity, by looking after your gut! 

By Julia Ebbens

When it comes to supporting our immune system, it all begins with the gut.  You may have heard the statistic that up to 80% of our immune system resides within the gut1. Well, we also have the capacity to improve the two key factors in gut-based immunity: the integrity of our intestinal lining and the diversity of microbes living within the gut. Here, we delve into some practical tips you can use to support your immunity, and can implement today! 

Your Gateway to Great Immunity

Our intestines contain a mucosal lining, which, when healthy, has tight junctions we can think of as ‘gateway,’ deciding which particles can enter2. Whilst digested food is given a free pass, unhelpful pathogens are less welcome3. It is easy to visualise that any gaps between these gates may permit pathogens to enter, triggering an immune response, which may, over time, weaken immunity against other invaders, such as viruses4.  Unfortunately, standard Western diets combined with a stressful lifestyle, antibiotic overuse and excessive alcohol consumption encourages these unhelpful ‘gaps’5.

Support your intestinal mucosal immunity by upping your intake of polyphenols such as resveratrol-rich blueberries and quercetin-rich apples.

Luckily, we can strengthen the integrity of the lining by encouraging short chain fatty acid production (SCFA)6, which, in turn, this supports immunity. We produce SCFA’s such as butyrate when microbes like Faecalibacterium and Roseburia feast on dietary fibers that are indigestible to us, but readily consumed by our microbiota7. Notably, we can feed these microbial strains by eating prebiotics, such garlic, asparagus and banana, and avoiding high fat/low carb diets8.  Another way to support your intestinal mucosal immunity is to up your intake of polyphenols such as resveratrol-rich blueberries and quercetin-rich apples9. Animal studies indicate polyphenols have the ability to protect intestinal mucosal immunity, as well as potentially down-regulate pro-inflammatory cytokines induced by certain viruses10.  

Polyphenols have the ability to protect intestinal mucosal immunity, as well as potentially down-regulate pro-inflammatory cytokines induced by certain viruses. 

Eating for Microbial Diversity

The microbes that reside in our gut play a key role in innate immunity11 – our first line of defense. Mice living without gut microbes don’t have the ability to differentiate between regular and pathogenic bacteria, therefore the immune system isn’t appropriately ‘primed’ for invaders12. Similarly, certain microbial strains such as Clostridia species (increased via a Mediterranean style diet8) encourage the modulation of Vitamin A, which may prevent immune system overactivity 13(as implicated in SARS type illnesses14). Interestingly, there is even research into the gut-lung axis, with suggestions that gut microbiota can ‘talk’ to the lung microbiota15, influencing inflammation and lung immunity.  What’s more, emerging evidence suggests that supplementary probiotic strains such as Lactobacillus casei may be of benefit in both the prevention and treatment of lung-based infectious diseases16

People in the Blue Zones (longest-living communities) have far greater diversity than average. 

Each time you’re eat, your feeding your microbial community too. Keep that in mind when making your next meal choice, and make sure to eat for your bugs too! A diverse microbiome is a healthy one17;  for instance, people in the Blue Zones (longest-living communities) have far greater diversity than average.18

Aiming for around 50 different, fiber-rich, plant-based foods per week is a good starting point. Try to make each meal nutritionally dense, trying to add just “one more,”) be it a portion of dark leafy greens, spoonful of sauerkraut or a handful of toasted seeds19.  Let’s crowd out the bad bugs with regular consumption of fermented foods- increasing Lactobacillus species means those pesky pathogens will have less space to settle in our gut lining11. It is also highly therapeutic to bake a loaf of sourdough or tend to a batch of kombucha!

Lifestyle interventions

  • Let the laughter out! It can be more challenging to stay upbeat when times are hard. Still, research highlights just how beneficial laughter can be for our immunity20. Find your own ways to feel the comedy in life – be it through an upbeat tv show or fun conversations with friends. 
  • Breathe deeply, and  establish peace, as the switch to a parasympathetic dominant nervous system reduces high circulating cortisol levels, which act as an immune suppressant21. This can include getting enough sleep, finding time to rest without distraction during the day, enjoying the warmth of the sunshine or taking time for something you love.
  • Move moderately, not excessively, since extreme exercise can deplete immunity22, but mild- moderate exercise can improve it23. In addition to its mood boosting effects, some gentle cycling or walking in the sun also adds immune boosting vitamin D24. If you are feeling brave, rounding it off with a dip in some cold water may help get those white blood cells firing up25!

Key Points

Remember to think of the three P’s

    • PREBIOTICS. Increase your intake of prebiotic foods, such as artichokes and asparagus, to support SCFA production and gut wall integrity. 
    • POLYPHENOLS. Eat more berries, red grapes and other foods rich in polyphenols in order to regulate your gut-based immune response and mucosal health.
    • PLANTS. Consume a wide variety of nutrient-dense plant foods, to fill you up and crowd out processed counterparts, and making sure to ferment some of them for a hefty probiotic dose too! 

References:

  1. Vighi G, Marcucci F, Sensi L, Cara G Di, Frati F. Allergy and the gastrointestinal system. Clin Exp Immunol. 2008;153(Suppl 1):3. doi:10.1111/J.1365-2249.2008.03713.X
  2. Chen B, Sun L, Zhang X. Integration of microbiome and epigenome to decipher the pathogenesis of autoimmune diseases. J Autoimmun. 2017. doi:10.1016/j.jaut.2017.03.009
  3. Odenwald MA, Turner JR. The intestinal epithelial barrier: a therapeutic target? Nat Rev Gastroenterol Hepatol. 2017;14(1):9-21. doi:10.1038/nrgastro.2016.169
  4. Postler TS, Ghosh S. Understanding the Holobiont: How Microbial Metabolites Affect Human Health and Shape the Immune System. Cell Metab. 2017;26(1):110-130. doi:10.1016/J.CMET.2017.05.008
  5. Fasano A. All disease begins in the (leaky) gut: role of zonulin-mediated gut permeability in the pathogenesis of some chronic inflammatory diseases. F1000Research. 2020. doi:10.12688/f1000research.20510.1
  6. Lazar V, Ditu LM, Pircalabioru GG, et al. Aspects of gut microbiota and immune system interactions in infectious diseases, immunopathology, and cancer. Front Immunol. 2018. doi:10.3389/fimmu.2018.01830
  7. Tamanai-Shacoori Z, Smida I, Bousarghin L, et al. Roseburia spp.: A marker of health? Future Microbiol. 2017. doi:10.2217/fmb-2016-0130
  8. Del Chierico F, Vernocchi P, Dallapiccola B, Putignani L. Mediterranean diet and health: Food effects on gut microbiota and disease control. Int J Mol Sci. 2014. doi:10.3390/ijms150711678
  9. Romier B, Schneider YJ, Larondelle Y, During A. Dietary polyphenols can modulate the intestinal inflammatory response. Nutr Rev. 2009. doi:10.1111/j.1753-4887.2009.00210.x
  10. Ding S, Jiang H, Fang J. Regulation of Immune Function by Polyphenols. J Immunol Res. 2018;2018:1-8. doi:10.1155/2018/1264074
  11. Shi N, Li N, Duan X, Niu H. Interaction between the gut microbiome and mucosal immune system. Mil Med Res. 2017;4(1):14. doi:10.1186/s40779-017-0122-9
  12. Lazar V, Ditu L-M, Pircalabioru GG, et al. Aspects of Gut Microbiota and Immune System Interactions in Infectious Diseases, Immunopathology, and Cancer. Front Immunol. 2018;9:1830. doi:10.3389/fimmu.2018.01830
  13. Grizotte-Lake M, Zhong G, Duncan K, et al. Commensals Suppress Intestinal Epithelial Cell Retinoic Acid Synthesis to Regulate Interleukin-22 Activity and Prevent Microbial Dysbiosis. Immunity. 2018;49(6):1103-1115.e6. doi:10.1016/j.immuni.2018.11.018
  14. Cameron MJ, Bermejo-Martin JF, Danesh A, Muller MP, Kelvin DJ. Human immunopathogenesis of severe acute respiratory syndrome (SARS). Virus Res. 2008. doi:10.1016/j.virusres.2007.02.014
  15. Enaud R, Prevel R, Ciarlo E, et al. The Gut-Lung Axis in Health and Respiratory Diseases: A Place for Inter-Organ and Inter-Kingdom Crosstalks. Front Cell Infect Microbiol. 2020;10:9. doi:10.3389/fcimb.2020.00009
  16. Mortaz E, Adcock IM, Folkerts G, Barnes PJ, Paul Vos A, Garssen J. Probiotics in the management of lung diseases. Mediators Inflamm. 2013;2013:751068. doi:10.1155/2013/751068