Microbiome and the immune system: a partnership

The gut microbiota not only aids in digestion, but also trains the immune system to recognize threats without overreacting . When the microbiome is balanced, immune cells function calmly and precisely. When this balance is disrupted (due to stress, poor diet, antibiotics, or too little fiber), dysbiosis occurs, a condition that promotes chronic inflammation and reduces resistance.

The gut microbiota doesn’t just serve digestion – it teaches immune cells to distinguish threats from allies . During the first years of life, environmental microbes “train” our immunity, stimulating the development of lymphocytes and helping to create immune tolerance – the ability for the body to not overreact to harmless substances, such as food or pollen.

Scientists have shown that microbiome deficiency (eg, in germ-free mice or children born by caesarean section) leads to poorer development of regulatory T-cells (Treg) and an increased risk of allergies and autoimmune diseases later in life.

Immunological mechanisms in the intestines

The intestines are our largest immune organ — more than 70% of immune cells are located in the intestinal mucosa . They create a physical and chemical barrier:

• Epithelial cells secrete antimicrobial peptides and mucus that prevent bacteria from contacting the intestinal walls.

• Immunoglobulin A (IgA) , produced by B-cells, limits the growth of potentially harmful microbes and preserves the “healthy” structure of the microbiome.

• If bacteria do pass the barrier, macrophages quickly phagocytize them, and dendritic cells (DCs) transport them to the lymph nodes where a controlled immune response is activated.

Microbial metabolites – small molecular wonders

One of the most interesting parts of this interaction is short-chain fatty acids (SCFAs) , such as butyrate, acetate, and propionate – byproducts of the fermentation of dietary fiber.
They act as epigenetic regulators : they reduce inflammatory processes, activate Treg cells and stimulate the production of IL-22 – a protein that strengthens the intestinal barrier.

Interestingly, when the microbiome is depleted (e.g., due to a fiber-free diet or frequent antibiotic use), SCFA levels drop, which may lead to weakened immune tolerance and a higher risk of inflammatory bowel disease (IBD).

Corn dextrin: a fiber that nourishes the microbiome and strengthens the immune response

The ingredient in Metabelly fiber ( Fiber Be Balanced ) is soluble corn fiber – a prebiotic fiber derived from corn.

Its specialty is that it ferments slowly in the colon , which feeds beneficial bacteria and stimulates the production of short-chain fatty acids (SCFA) such as butyrate and propionate – substances that calm inflammation and strengthen the intestinal barrier.

According to a clinical trial published in Frontiers in Immunology (Costabile et al., 2017), daily consumption of 6 g of SCF in combination with probiotics for 3 weeks in elderly subjects:

• It reduced levels of the inflammatory cytokine IL-6 , which is associated with chronic inflammation and immune-senescence .

• Increased activity of natural killer cells (NK cells) – crucial for defense against viruses and tumor cells – especially in women and people over 70 years of age.

• Increased the proportion of beneficial bacteria of the genus Ruminococcaceae and Parabacteroides , which produce butyrate and contribute to a stable intestinal microflora.

• Reduced LDL cholesterol and total cholesterol in people with elevated levels.

In other words, it acts not only as a fiber, but as a modulator of the microbiome and immunity .

How does it work?

Fermentation of corn fiber in the intestines produces short-chain fatty acids (SCFA) that:

• stimulate the growth of protective bacteria such as Bifidobacterium and Faecalibacterium ,

• reduce the secretion of inflammatory cytokines (e.g. IL-6, TNF-α),

• increase the production of immunoglobulin A (IgA) , which protects the intestinal mucosa,

• They support epithelial regeneration and strengthen the intestinal barrier – our first line of defense.

Nutrition and lifestyle that help

In order for the microbiome to work in favor of immunity, it is important to have a varied diet and a sufficient amount of fiber along with probiotics.

Include:

• Prebiotics : oats, asparagus, leeks, bananas, garlic

• Fermented foods : sauerkraut, kimchi, kefir, kombucha

• Polyphenols : blueberries, green tea, cocoa, olive oil

• Quality sleep and moderate activity – because rhythm and stress also affect the intestinal ecosystem

A healthy immune system begins where we least expect it — in the gut.

If you want to find out how your microbiome supports your immunity, take a Metabelly microbiome analysis and discover what your gut bacteria say about your resistance.