Consumption of only wild foods induces large scale, partially persistent alterations to the gut microbiome.

The gut microbiome (GM) is implicated in human health and varies among lifestyles. So-called "traditional" diets have been suggested to promote health-associated taxa. However, most studies focused only on diets including domesticated foods. Historically, humans consumed only wild foods, which might uniquely shape GM composition. We explored the impact of a wild-food-only diet on GM, particularly whether it increases the presence of health-associated and/or "old friend" taxa, and if the alterations to GM are persistent or transient. One participant collected daily fecal samples and recorded daily food consumption over an eight-week period, the middle four weeks of which he consumed only wild foods. Samples were profiled by 16S rRNA sequencing, and oligotyping and network analysis were conducted to assess microbial co-occurrence patterns. A wild-food-only diet considerably alters the composition of the GM, and the magnitude of the changes is larger than that observed in other diet interventions. No new taxa, including "old friends" appeared; instead, the proportions of already-present taxa shifted. Network analysis revealed distinct microbial co-abundance groups restructuring across dietary phases. There is a clear successional shift from the pre-, during- and post-wild-food-only diet. This analysis highlighted structural and functional shifts in microbial interactions, underscoring diet's role in shaping the gut ecosystem.