XIV. 1. Cultural and Ancestral Diets

Traditional, minimally processed, fiber-rich diets sustain a diverse microbiota shaped over millennia, which a Western diet can narrow within a single generation.

Your Ancestors' Plate Still Feeds Your Microbiota Today

The traditional diet of your culture plays a crucial role in shaping and preserving gut microbial diversity [257].

The microbiota^[G] consequences of ancestral diet patterns were characterized through comparative genomic and metagenomic analysis of traditional and industrialized populations. The Hadza of Tanzania, who consume an ancestral diet of tubers, honey, berries, and wild game with no ultra-processed foods, antibiotics, or agricultural chemicals, were studied by Schnorr and colleagues in a paper published in Nature Communications in 2014. Hadza gut microbiota showed bacterial taxa not found in industrialized Western populations, including abundant spirochaetes and unclassified organisms that have been functionally associated with plant fiber fermentation. [334] The most striking comparison came from the Human Food Project's analysis of the American Gut Project data alongside Hadza data: the average American adult gut microbiota harbored approximately 1,200 unique microbial taxa, while the average Hadza adult harbored over 1,700 unique taxa. The difference was not merely quantitative – it was qualitative, with entire bacterial genera present in the Hadza microbiota that are functionally absent from Western populations. These include multiple Treponema species (intestinal, non-pathogenic relatives of the syphilis spirochete) and Spirochaeta species that carry extensive polysaccharide fermentation capacity. [24] The mechanisms by which ancestral diets maintain this diversity include: daily consumption of 100+ grams of dietary fiber from diverse plant sources, feeding dozens of fermentable substrates simultaneously; regular consumption of fermented foods prepared through traditional methods with diverse starter communities; absence of ultra-processed foods that suppress microbial diversity by providing easily absorbed substrates that bypass colonic fermentation; and regular contact with soil, plants, and animals that seed the gut with environmental organisms. [257] The clinical implication is not romantic – it does not suggest returning to hunter-gatherer subsistence. It identifies specific dietary components (diverse fiber types, fermented foods, minimal processing) and environmental inputs (soil contact, biodiversity exposure) that maintained ancestral microbiota diversity, and that can be targeted in contemporary dietary guidance.

When patients ask why “traditional food” matters, I usually start with a practical point: the gut microbiota responds to patterns. It is shaped less by a single meal and more by what a person eats repeatedly over months and years. Cultural dietary habits are one of the most stable long-term patterns many people share with their families and communities [39].

Across regions, many traditional dietary patterns had a few common features: they relied on minimally processed staples, included a wide variety of plant foods, and often used fermentation. These foods supply complex carbohydrates and plant fibers that humans do not fully digest on their own. Microbes ferment them, producing metabolites such as short-chain fatty acids^[G], which support epithelial function and interact with mucosal immune regulation.

Comparative studies of different populations consistently show that gut microbial profiles differ between highly industrialized settings and more traditional lifestyles. High-fiber diets are often associated with a more fermentation-oriented community structure, including higher representation of fiber-utilizing groups such as Prevotella in some cohorts. In contrast, diets that are low in fiber and high in ultra-processed foods tend to correlate with reduced fermentative capacity and different dominant taxa.

It is important to avoid oversimplification. These population differences are not explained by diet alone. Urbanization, sanitation, antibiotic exposure, infection burden, and overall lifestyle all shape microbial ecology. “Traditional” does not automatically mean “health-promoting,” and “diversity” alone is not a clinical diagnosis. Still, dietary structure remains one of the most modifiable drivers.

Some organisms that are more frequently detected in non-industrialized populations—such as Prevotella and, in certain groups, spirochetes like Treponema—should be interpreted as markers of sustained ecological inputs, especially high fiber intake, rather than as therapeutic targets. Their presence often reflects what the ecosystem is being fed, not a single protective species.

One reason modern diets change the microbiota so effectively is speed. Short-term diet experiments show that microbial composition and gene expression can shift within days when macronutrient patterns change. That responsiveness is useful clinically, but it also means that “heritage” is not destiny; the microbiota remains adaptable throughout life.

Reconnecting with elements of a traditional dietary structure can therefore be understood as restoring microbial substrates, not recreating history. When patients increase plant variety, legumes, whole grains, and fermented foods—within what they tolerate—the microbiota often shifts toward a more fermentative metabolic profile. The most consistent changes are functional first (metabolites and activity), while stable compositional changes may take longer.

In practice, the goal is not a rigid ancestral menu. It is to rebuild dietary complexity that modern food systems often remove: more minimally processed foods, more plant diversity, and more regular exposure to fermentable fibers. This approach supports ecological resilience in the gut, which matters when life becomes stressful, travel disrupts routines, or illness reduces appetite.

So the “ancestors’ plate” is best seen as a framework. It reminds us that the microbiota thrives on consistent, complex inputs. When modern diets become too simplified, microbial ecosystems narrow. When complexity returns—sustainably and realistically—the gut environment becomes more stable, and the microbiota has better conditions to function well.

Integrating Traditional Dietary Patterns into Modern Life

Reintroducing elements of traditional cuisine is most practical when approached gradually, focusing on familiar dishes built around minimally processed grains, legumes, vegetables, and fermented foods.

Regular inclusion of diverse plant foods provides fermentable substrates that support microbial metabolic activity, rather than targeting specific bacterial species.

Traditional preparation techniques—such as soaking, fermenting, or slow cooking—can improve digestibility and nutrient availability without requiring strict adherence to historical recipes.

Limiting ultra-processed foods and sweetened beverages reduces exposure to additives and refined carbohydrates that may alter microbial metabolic pathways.

Seasonal and locally available produce can help increase dietary variety over time, which appears more important for microbial function than any single ingredient.

Meals prepared and eaten in consistent routines often support better digestion through behavioral mechanisms such as slower eating and more regular meal timing.

Traditional dietary fats, when used within balanced meals rich in fiber and plant diversity, contribute to satiety and may influence absorption of fat-soluble compounds without requiring specific fat prescriptions.

Family or community cooking practices can help maintain dietary consistency, which is one of the strongest drivers of long-term microbial adaptation.

The clinical goal is not to recreate a historical menu, but to restore dietary complexity that supports microbial metabolism in a sustainable way.

Microbiota Effects

• Long-term diets rich in diverse plant fibers are associated with greater microbial functional diversity, including increased capacity for complex carbohydrate fermentation and short-chain fatty acid^[G] production [334].
• High-fiber dietary patterns often correlate with higher relative abundance of fiber-utilizing taxa such as Prevotella in some populations, and butyrate (a short-chain fatty acid that is the primary energy source for colonocytes) (a short-chain fatty acid that nourishes colon cells and reduces inflammation)-producing organisms such as Faecalibacterium prausnitzii^[G] in others; these taxa are markers of dietary substrates rather than universal indicators of health [24].
• Fermented foods can introduce live microorganisms and fermentation-derived metabolites; most strains do not permanently colonize the gut but may transiently influence microbial activity and immune signaling.
• Diets high in ultra-processed foods and low in fermentable fiber are associated with reduced microbial metabolic diversity and altered bile-acid and short-chain-fatty-acid pathways, rather than with a single identifiable “harmful species.”
• Increased intake of plant polysaccharides and resistant starch can enhance production of metabolites such as butyrate, acetate, and propionate, which interact with epithelial integrity, mucosal immunity, and gut–brain signaling.
• Certain taxa commonly observed in high-fiber populations—such as Prevotella or, in some traditional communities, spirochetes like Treponema—should be interpreted primarily as ecological markers of dietary structure rather than therapeutic targets.
• Fermented foods and traditional dietary diversity may influence not only bacteria but also gut fungi and bacteriophages^[G], although these effects are less well characterized in humans.
• Early-life diet patterns shape microbiota development and immune training; continued dietary patterns in families and communities contribute to shared microbial profiles through both environmental exposure and shared foods.
• Reduced exposure to dietary emulsifiers and certain additives may influence mucus integrity and microbial localization in experimental models, though human evidence remains limited.
• Overall, traditional high-fiber dietary structures appear to support microbial metabolic resilience rather than guaranteeing specific compositional outcomes.

Patient Guidance

• Choose meals based on whole grains, legumes, vegetables, and minimally processed foods.
• Include a variety of plant foods each week to increase fermentable fiber intake.
• Add fermented foods that you tolerate well, such as yogurt, kefir, or sauerkraut.
• Replace ultra-processed snacks with simple fiber-rich options like nuts, beans, or cooked grains.
• Keep regular meal times and eat slowly to support digestion.
• Try traditional preparation methods such as soaking beans or slow cooking grains when practical.
• Use herbs and spices for flavor instead of relying on packaged sauces.
• Keep changes gradual to allow the gut to adapt.
• Maintain consistency for several weeks before judging the effect.

References

[24] Sonnenburg JL, Bäckhed F. Diet–microbiota interactions as moderators of human metabolism. Nature. 2016. Link

Review of mechanisms linking the gut microbiota to obesity and type 2 diabetes drawing on translational animal models and human studies. The microbiota emerges as a mediator of dietary impact on host metabolic status, with growing efforts to establish causal relationships in people and develop therapeutic interventions including personalised nutrition.

[39] Koh A, De Vadder F, Kovatcheva-Datchary P, Bäckhed F. From Dietary Fiber to Host Physiology: Short-Chain Fatty Acids as Key Bacterial Metabolites. Cell. 2016. Link

Mechanistic review of short-chain fatty acids (SCFAs) — a major class of bacterial metabolites derived from dietary fibre fermentation — as central mediators between diet, gut microbiota, and host physiology. SCFAs activate G-protein-coupled receptors, inhibit histone deacetylases, and serve as energy substrates, thereby influencing metabolic, immune, and epigenetic processes. The authors synthesize evidence implicating SCFA-mediated signalling in both health maintenance and disease pathogenesis. Provides the conceptual backbone for fibre-based and microbiome-directed therapeutic strategies.

[257] Rook, G. A. Regulation of the immune system by biodiversity from the natural environment. Proc Natl Acad Sci USA. 2013. Link

This review summarizes evidence that proximity to natural environments associates with reduced mortality, cardiovascular disease and psychiatric morbidity. The authors highlight that rising chronic illness in high-income countries is associated with failing immunoregulation and persistent low-grade inflammation, partly attributable to lost exposure to evolutionarily co-adapted Old Friends microorganisms. The hypothesis links biodiversity-rich environments to immunoregulatory training that protects against chronic inflammatory disease. The findings reframe green-space exposure as immunological rather than purely psychological intervention.

[334] Schnorr SL, Candela M, Rampelli S et al. Gut microbiome of the Hadza hunter-gatherers. Nat Commun. 2014. Link

The authors profiled the gut microbiome of Hadza hunter-gatherers in Tanzania and compared it with rural African farming populations and Italian urban controls. The Hadza exhibited markedly higher microbial richness and biodiversity than urban controls. Their microbiota lacked Bifidobacterium, showed sex differences linked to the sexual division of foraging labor, and was enriched in Prevotella, Treponema and unclassified Bacteroidetes, plus a distinct arrangement of Clostridiales. These features likely support efficient extraction of nutrition from fibrous plant foods. The findings illustrate microbiota co-evolution with subsistence strategy and challenge assumptions about a universal healthy microbiome.