Eating only wild foods reshapes your gut microbiome in just weeks, study shows

By Vijay Kumar MalesuReviewed by Susha Cheriyedath, M.Sc.May 14 2025

An all-wild diet triggers a gut microbial makeover, boosting fiber-degrading bacteria and reshaping the ecosystem in ways that persist even after returning to regular foods.

Study: Consumption of only wild foods induces large scale, partially persistent alterations to the gut microbiome. Image Credit: CI Photos / Shutterstock

In a recent study published in the journal Scientific Reports, researchers investigated how a diet consisting exclusively of wild foods influences the composition, structure, and persistence of changes in the gut microbiome (GM) in modern humans.

Background

What happens when we stop eating anything cultivated or processed? Many urban populations consume mass-produced, high-sugar, and low-fiber diets that can disrupt GM balance. In contrast, “traditional” populations consuming fiber-rich, minimally processed foods tend to have greater microbial diversity linked to better immunity and lower inflammation.

Prior research shows that diet changes can reshape the GM, but most studies remain within the boundaries of industrial diets based on domesticated foods. Since early humans relied on wild foods, studying this pattern could offer insights into our evolutionary biology. Further research is needed to validate these findings in diverse populations.

About the study

One healthy adult male, aged 46, followed an eight-week self-monitored diet protocol divided into three phases: two weeks of a normal diet, four weeks of wild-food-only diet, and two weeks returning to a normal diet.

The wild foods, available in northern Europe during autumn, were gathered and prepared using primitive techniques like open-fire cooking and grindstones. The participant maintained his usual lifestyle and lived in his own home, isolating dietary influence from other variables. He was an experienced forager, and his health and well-being were monitored daily, with all food intake meticulously logged.

Stool samples were collected daily and stored at -20°C. Microbial Deoxyribonucleic acid (DNA) was extracted, and the V3–V4 regions of the 16S ribosomal Ribonucleic acid (rRNA) gene were sequenced using the Illumina MiSeq platform. Amplicon sequence variants (ASVs) were determined with Divisive Amplicon Denoising Algorithm 2 (DADA2) and taxonomically classified using the Systematic Initiative for Large-scale Verification of Alignments (SILVA) database.

Species-level analysis used the Genomes from Earth’s Microbiomes (GEM) catalog. Co-abundance networks were built using Kendall’s correlation and visualized in Cytoscape to identify keystone taxa.

Functional potential was inferred using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) and Kyoto Encyclopedia of Genes and Genomes (KEGG) ortholog analysis. Comparative analysis included microbiomes from hunter-gatherer, rural, and urban-industrial populations.

Statistical tests, including Kruskal-Wallis and Wilcoxon rank-sum, were applied, and adjustments for multiple testing were made using the Benjamini-Hochberg procedure with a false discovery rate of ≤ 0.05.

Study results

During the wild-food-only diet, the participant’s GM underwent substantial changes in structure and diversity. Initial microbial communities were dominated by typical Western-associated taxa like Bacteroidaceae, Ruminococcaceae, and Bifidobacteriaceae.

As the wild-food diet began, there was a marked shift with a decrease in these groups and an increase in families such as Lachnospiraceae, Butyricicoccaceae, and Streptococcaceae. Notably, Bifidobacteriaceae and Rikenellaceae did not revert to pre-diet levels even after the participant resumed his regular diet. The family Akkermansiaceae, particularly Akkermansia muciniphila, increased significantly in the post-wild-food period, a finding associated with metabolic benefits.

The wild-food diet also led to significant weight loss, 4 kg over four weeks, with the greatest loss during the first week. The participant reported boredom and limited food choices, contributing to reduced caloric intake. Two kilograms were quickly regained upon returning to a normal diet. This weight loss was attributed in part to caloric restriction and the monotony of available foods.

A gradual increase in microbial alpha diversity was observed from the pre-wild-food period, through the wild-food and into the post-wild-food period (P < 0.05), indicating that the intervention had a persistent effect on the microbiome structure even after its conclusion. Keystone species also shifted.

Prior to the intervention, Faecalibacterium prausnitzii played a central role in the microbial network. During the wild-food phase, Blautia and its associated taxa, known for fiber degradation and short-chain fatty acid (SCFA) production, dominated the network.

Six microbial co-abundance groups (CAGs) were identified. These groups reorganized based on the diet phase, suggesting functional reassembly of the ecosystem. Faecalibacterium prausnitzii, Ruminococcus bicirculans, and Blautia emerged as key influencers at different times. The post-wild-food period showed an intermediate configuration, with some traits resembling the pre-diet phase, and others, such as the persistence of certain Blautia and Coprococcus comes groups, reflecting a lasting impact of the intervention.

Despite this transformation, no new or ancestral “old friend” taxa such as Treponema or Prevotella appeared. The changes were driven solely by shifts in abundance among already-present taxa, not by the introduction of new species. This finding suggests that even substantial dietary changes may be insufficient to reacquire lost ancestral microbial taxa without additional environmental exposures.

Functional predictions revealed enhanced capabilities for starch degradation and amino acid biosynthesis during the wild-food period, likely in response to a diet high in chestnuts and acorns but low in animal proteins. Functional analysis also indicated increased capacity for degradation of environmental chemicals such as atrazine, likely reflecting exposure to wild plants gathered from previously agricultural lands.

Compared to other interventions, such as adopting a plant-only or animal-only diet, the shift caused by wild-food consumption was larger in magnitude. Measured by beta diversity, the shift induced by wild-food consumption was greater than that observed in plant-only or animal-only dietary interventions, though the microbiome did not fully resemble that of traditional or hunter-gatherer populations. Instead, it evolved into a unique composition influenced by the available taxa and dietary inputs. The state after resuming a normal diet was intermediate, sharing features of both pre- and wild-food phases.

The persistence of some microbial configurations post-intervention suggests a partial but lasting reconfiguration. Notably, the Blautia-dominated network did not completely recede, indicating that certain changes to the gut ecosystem could outlast the diet itself.

However, this was an N=1 study, and findings may not be broadly generalizable. The potential effects of the participant’s change in mood during the wild-food diet and his specific genetic and dietary history remain unexplored.

Conclusions

To summarize, this study reveals that switching to a diet made entirely of wild, non-domesticated foods leads to a major reorganization of the human GM. While no new taxa were introduced, the composition and function of existing microbes shifted significantly, increasing fiber-degrading species like Blautia and decreasing dairy-associated taxa such as Bifidobacterium.

These microbial changes persisted even after resuming a normal diet, highlighting the microbiome’s adaptive capacity. Although the absence of ancestral taxa like Treponema suggests limitations in fully restoring a traditional microbiome, this experiment underscores the powerful influence of diet alone in reshaping gut health, even in a modern setting.

Further research is required to investigate the metabolic and immunological consequences of these microbiome changes in larger and more diverse populations.