Ancestral Diet Series

When people think about improving their gut health, fiber usually gets all the attention. We have been told for years to "eat more fiber," and while that's certainly good advice, it isn't the whole story.

Our ancestors didn't just eat fiber-rich foods—they regularly consumed living foods. Before refrigeration and food processing, fermentation was one of the primary ways people preserved vegetables, milk, and other foods. Along the way, they unknowingly cultivated trillions of beneficial microbes that helped nourish the gut.

Today, we have largely replaced these traditional foods with ultra-processed products that are sterile, shelf-stable, and often devoid of living microorganisms. As a result, many of us are missing one of the oldest tools for supporting a healthy microbiome.

Fiber Builds the Neighborhood—Fermented Foods Bring in New Neighbors

One study that attracted considerable attention came from Stanford University in 2021. Researchers randomly assigned healthy adults to either a high-fiber diet or a high-fermented-food diet for ten weeks.

The results surprised many researchers.

The group eating fermented foods experienced:

• Increased microbial diversity

• Reductions in numerous inflammatory proteins

• Improvements that became stronger as fermented food intake increased

Meanwhile, the high-fiber group increased the activity of their existing gut microbes but did not significantly increase microbial diversity during the ten-week study.

This does not mean fiber doesn't matter.

Quite the opposite.

Fiber remains the primary fuel for your existing beneficial bacteria. It is converted into short-chain fatty acids like butyrate that nourish the cells lining your colon, regulate inflammation, and support metabolism.

What the Stanford study suggests is that fiber and fermented foods perform different jobs.

Think of your gut like a garden.

Fiber is the compost that feeds the plants already growing there.

Fermented foods are like introducing new beneficial seeds and gardeners while also providing beneficial compounds they have already produced during fermentation.

The healthiest microbiome is likely built by combining both.

Why Fermentation Changes Food

Fermentation is essentially "pre-digestion."

Beneficial bacteria and yeasts begin breaking down food before you eat it.

During this process they can:

• Produce organic acids

• Synthesize certain B vitamins

• Produce vitamin K₂ (depending on the microbes involved)

• Reduce antinutrients such as phytates

• Improve mineral absorption

• Partially break down proteins and carbohydrates

• Produce beneficial metabolites that may influence immune function

This is one reason many people find fermented foods easier to digest than their unfermented counterparts.

More Than Just Probiotics

One of the biggest misconceptions is that fermented foods work simply because they contain probiotics.

While they certainly contain living microbes, they also provide something equally important: postbiotics.

Postbiotics are beneficial compounds made during fermentation, including:

• Organic acids

• Enzymes

• Bioactive peptides

• Exopolysaccharides

• Bacteriocins (natural antimicrobial compounds)

• Vitamins

These compounds can continue benefiting your gut even if the microbes themselves do not permanently colonize your intestines.

In other words, fermented foods nourish your microbiome in multiple ways.

Nature's Original Functional Foods

Different fermented foods contribute different microbes and nutrients.

Fermented Vegetables

Sauerkraut, kimchi, fermented carrots, cucumbers, beets, and other vegetables often contain Lactobacillus species that help maintain a healthy gut environment.

Fermentation also increases the bioavailability of many nutrients and creates beneficial organic acids.

Milk Kefir

Milk kefir is one of the most diverse fermented foods known, often containing dozens of bacterial and yeast species. It provides protein, calcium, vitamin K₂ (depending on preparation), B vitamins, and beneficial microbes.

Many people who struggle with lactose digestion tolerate kefir surprisingly well because much of the lactose has already been fermented.

Yogurt

Traditional yogurt supplies beneficial bacteria while also serving as an excellent source of protein and calcium.

Certain specialized cultures, such as Limosilactobacillus reuteri and Lacticaseibacillus gasseri, are currently being studied for potential benefits involving gut health, immune regulation, skin health, and metabolism. Although early findings are promising, research is still evolving.

Natto

Natto is one of the richest dietary sources of vitamin K₂ and contains the enzyme nattokinase, along with beneficial Bacillus subtilis. It remains a staple food in Japan and has been associated with bone and cardiovascular health.

Kombucha

Kombucha provides organic acids, polyphenols derived from tea, and living microorganisms. While many people enjoy it as part of a healthy diet, many of its more dramatic health claims still require stronger clinical evidence.

Not Everyone Should Dive In

Although fermented foods are healthy for many people, they are not appropriate for everyone immediately.

Individuals with:

• Histamine intolerance

• Mast cell activation syndrome (MCAS)

• Significant small intestinal bacterial overgrowth (SIBO)

• Severe digestive disorders

may initially react to fermented foods.

In these situations, beginning with very small amounts and gradually increasing intake often works better than jumping into large servings.

As always, listen to your body.

Fermented Foods Are Only Part of the Story

No single food creates a healthy microbiome.

Your gut thrives on diversity.

That means combining fermented foods with an ancestrally inspired eating pattern rich in:

• Colorful vegetables

• Fruits

• Herbs and spices

• Resistant starches

• Nuts and seeds

• Pasture-raised meats

• Wild-caught seafood

• Healthy animal fats

• Polyphenol-rich foods such as berries, olives, green tea, cocoa, and herbs

Each feeds different members of your microbial community.

Bringing Back an Ancient Tradition

Fermentation is not a modern wellness trend.

It is one of humanity's oldest food preservation techniques.

For thousands of years, people routinely consumed sauerkraut, kefir, yogurt, cultured vegetables, naturally fermented pickles, and other living foods. These foods likely played an important role in maintaining microbial diversity long before anyone knew bacteria even existed.

Perhaps one reason chronic inflammatory diseases are so common today is that we've replaced these living foods with ultra-processed foods that have been stripped of both nutrients and microbes.

Returning to these ancestral practices doesn't require expensive supplements or complicated protocols. Start by adding one serving of a fermented food each day while continuing to eat a diet rich in diverse fibers and colorful plant foods.

Your microbiome—and the rest of your body—will thank you.

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