Feeding the Gut Microbiome to Support Immune Function

By: Jason Mertz, Dietetic Intern JJPVAMC Class of 2019


What is the Gut Microbiome?

The gut microbiome is the total of the influence in our intestines of microorganisms including bacteria, archaea, fungi, protozoa, and viruses. This often is a symbiotic relationship, where we are providing a home, safety and food to the many species, and they provide us with nutrients including Vitamin K, B complex and some beneficial fats, while promoting our immune function and lowering risk of infections. However, everyone has differences in the variety of their microbiome. This can be affected by where you live, weight, diet, age, antibiotics and many other factors.1

How does it affect Immune Function?

There are several ways that having a healthy microbiome effects immunity. Simplest is that having a large amount of neutral or beneficial bacteria leaves less space and food available for the pathogenic bacteria. Many bacteria, and fungi produce antimicrobial chemicals as well[1]. Beneficial protozoa may selectively eat bacteria[2]. Fats produced by the bacteria are absorbed and help to stimulate the immune system. This can be through production of proteins that reduce inflammation and stimulating production of antibodies. Species of bacteria including B. Longum, B Infantis, B. Breve, and L. Paracasei have been found to reduce symptoms of allergic rhinitis, while improving immunity to viral infections including influenza, bacterial infections including E. Coli, Salmonella, and H. Pylori, and improving tumor suppression.1

What foods affect the microbiome?

Diets which are high in processed foods, fried food, sugar and fats, can negatively affect the ratio of bacteria. This can result in distress in the intestines allowing increased permeability leading to infection and metabolic disease[3]. Diets rich in prebiotics (food for the bacteria) and probiotics (good bacteria) can lead to improved diversity and stability of beneficial bacteria[4], resulting in a stronger immune system.

Prebiotics are parts of food items, which we cannot digest but our good bacteria love to feed on. These substances are fermented by beneficial bacteria in the colon and provide strength in diversifying the gut microbiome. Prebiotics consist of dietary fiber, and oligosaccharides (non-digestible sugars)[5]. Some foods high in prebiotics properties include: beans, garlic, onions, leeks, asparagus, bananas, apples, cocoa, wheat bran, flaxseed, oats and leafy greens.

Probiotics, another term for the beneficial microorganisms found in foods, beverages, and supplements which introduce viable amounts of these beneficial microorganism to our biome when we consume them. Much like the biome itself, probiotic can differ greatly in what types of bacteria are present, the ratio of different bacteria, and the results you may find from starting one.1 Foods which may be a rich sources of probiotics include many fermented foods. Soy products containing probiotics include: tempeh, miso, and natto. Other vegetable-based sources include: sauerkraut, kimchi, and pickles. Kombucha is a popular fermented black or green tea, which contains both bacteria and yeast. Dairy products include yogurt, kefir, and even some aged cheeses may provide probiotics as well[6].

[1] Carlo C. Lazado and Christopher Marlowe A. Caipang, "Mucosal Immunity and Probiotics in Fish," Fish and Shellfish Immunology 39, no. 1 (Jul, 2014), 78-89. doi:10.1016/j.fsi.2014.04.015. https://www.sciencedirect.com/science/article/pii/S1050464814001314.


[2] Magali Chabé, Ana Lokmer and Laure Ségurel, "Gut Protozoa: Friends Or Foes of the Human Gut Microbiota?" Trends in Parasitology 33, no. 12 (Dec, 2017), 925-934. doi:10.1016/j.pt.2017.08.005. https://www.sciencedirect.com/science/article/pii/S1471492217302106.


[3] Sittipo et al., "Intestinal Microbiota and the Immune System in Metabolic Diseases," Journal of Microbiology 56, no. 3 (Mar, 2018), 154-162. doi:10.1007/s12275-018-7548-y. https://www.ncbi.nlm.nih.gov/pubmed/29492872.


[4] Lazado and Caipang, "Mucosal Immunity and Probiotics in Fish," Fish and Shellfish Immunology 39, no. 1 (Jul, 2014), 78-89. doi:10.1016/j.fsi.2014.04.015. https://www.sciencedirect.com/science/article/pii/S1050464814001314.


[5] Carlo C. Lazado and Christopher Marlowe A. Caipang, "Mucosal Immunity and Probiotics in Fish," Fish and Shellfish Immunology 39, no. 1 (Jul, 2014), 78-89. doi:10.1016/j.fsi.2014.04.015. https://www.sciencedirect.com/science/article/pii/S1050464814001314.


[6] Hrefna Palsdottir, "11 Probiotic Foods that are Super Healthy," https://www.healthline.com/nutrition/11-super-healthy-probiotic-foods (accessed Dec 12, 2018).