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Boosting the Immune System through Prebiotics

During the cold months, and particularly in this pandemic year, we are all thinking of our immune system and how well it will perform to defend us from invaders. Health and wellness begins in the digestive tract where a majority of our microbiome lives- you know, all that good bacteria that act as a part of our immune system. In fact, nearly 70% of the immune system is housed here. Focusing on nourishing our existing bacterial army through prebiotic plant fibers becomes even more important than just taking a probiotic.

Our good bacteria, otherwise known as our microbiome, act as a bacterial army protecting us from bad bacteria and viral invaders. 90% of our microbiome resides and colonizes in the large intestine. Here they feast on specific plant fibers called prebiotics, which provide their nourishment, allowing them to grow and thrive as a community. These bacteria purposefully reside in the large intestine since it has a structure and ecosystem designed to handle the fermentation process which occurs between microbe and fermentative fiber. Anyone who has ever experienced SIBO - small intestinal bacterial overgrowth- knows exactly what Im talking about.

Nourishing our bacterial army with specific prebiotic plant fibers becomes paramount to enabling a strong immune response against any invader. And as I mentioned, providing these prebiotic fibers is arguably even more important than just taking a probiotic. You can try to put new bacteria down there through probiotics but science is showing that is not always a guaranteed strategy. It is what keeps them alive, nourished, and thriving that will allow for a healthy bacterial community.

But not all dietary plant fibers are prebiotic fibers. Inulin, resistant starch, and oligosaccharides make up the main categories of prebiotic fibers. What makes them special is that they pass all the way through the gastrointestinal tract intact until they hit the large intestine and the bulk of our microbiome. Here they are munched on, broken down, and processed spawning the fermentation process and producing short chain fatty acids as well as other important by products beneficial to our wellbeing.

My Roasted Cauliflower & Mushroom Soup contains three great sources of prebiotics- cauliflower, alliums, and mushroom. It is a powerhouse of fermentative fiber and immune support that has become a staple in my house, especially during the colder months, particularly this year. I hope it becomes a go to for you and helps to protect you and your family this year and every year.


Through the prebiotic fiber beta glucan, cruciferous vegetables like cauliflower hold a significant impact on the diversity of our microbiome and its composition. By supporting our bacterial army, mainly the bifidobacterial species, our immune system is stronger and able to take on invaders. Cauliflower also works really well in soups and stews and becomes the star of this soup.


High in the prebiotic fiber inulin- all alliums including onions, leeks, shallots, and garlic are rich in this prebiotic fiber. Bonus- garlic is high in the bioactive compound allicin which is a natural antimicrobial- thus it not only promotes good bacterial growth but helps to eliminate the bad ones.


When it comes to immunity, mushrooms are particularly special. Not only do they contain prebiotic fibers like chitin and mannan proven to grow beneficial bacteria, but it also affects our immune system by enhancing lymphocytes, macrophages, T cells, dendritic and natural killer cells of the immune system.

Roasted Cauliflower & Mushroom Soup


1 head of cauliflower

3 Tbsp extra virgin olive oil

10-12 oz of mushrooms, chopped

1 yellow onion, chopped

1 shallot, chopped

2-3 cloves garlic, minced

1 tbsp dried oregano

1 bay leaf

6 cups of bone broth or water


  1. Wash cauliflower and break into florets. Spread florets on a baking sheet and coat with 2 tbsp olive oil. Season with salt as desired and toss well. Roast at 400 degrees F for 20 to 25 minutes.

  2. Meanwhile, in a large sauce pan, heat remaining oil on medium heat and sauté onion, shallot, and garlic until translucent. Add mushrooms and oregano, sauté with allium mix for 5-10 minutes, until mushrooms are broken down and well incorporated.

  3. Add roasted cauliflower to saucepan stirring to incorporate well. Add liquids and bay leaf, allowing to come back to a simmer. Keep simmering for 15 minutes more.

  4. Take an immersion blender and puree until smooth. Taste and add any extra salt and pepper per taste. Allow to simmer 5 more minutes. Serve with crusty bread or a dollop of sour cream.


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