You've probably heard that eating more plants is good for your gut. Most of us know yogurt, kimchi and a bit of fiber are supposed to help. What you may not know is how much seems to have already slipped out of the picture.
A Stanford-led study published October 7, 2026, in Nature compared the gut bacteria of two remote populations with modern Western guts.
Hundreds of bacterial species carried by hunter-gatherers and forager-farmers are rare or absent in people living industrialized lives.
The researchers deep-sequenced stool from the Hadza of Tanzania and the Tsimane of the Bolivian Amazon. These two groups have lived apart for thousands of years.
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Even so, they share around 1,231 gut bacterial species. That overlap covers roughly 87 percent of the Tsimane microbiome. About 60 percent of those shared bacteria are rare or absent in industrialized guts.
The gap is wide at the person level too. A Hadza individual carries around 750 microbial species on average. A Tsimane carries about 1,400. The average Californian in the comparison hosts around 250.
Justin Sonnenburg, senior author and a Stanford professor of microbiology, says these missing bacteria were ancient companions of humans. He describes them as likely passed down from generation to generation for millennia.
Losing them so quickly, he argues, could have real consequences for how healthy we are today.
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What modern life appears to have stripped away
Three ordinary shifts in daily life have pushed many of these bacteria toward disappearance over just a few generations: antibiotic exposure, processed food low in fiber and high in fat and sugar, and highly sanitized homes and water supplies.
Industrialized populations also have higher rates of autoimmune disease, type 2 diabetes and obesity. The Hadza and Tsimane have significantly lower rates of all three.
The researchers do not claim the missing bacteria cause the rise in chronic disease. But the long shared history, they argue, means this rapid loss is worth taking seriously.
What you can actually do today
The study is not a diet plan. It does support two habits researchers have been pointing to for years: more fiber from a wider range of plants, and more fermented foods.
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Fiber feeds the bacteria already living in your gut. Without enough of it, some microbes can start eating the gut's own mucus lining.
Common sources include beans, lentils, oats, whole grains, nuts, seeds, fruit and vegetables.
A 10-week Stanford trial published in 2021 followed 36 adults. Those who ate plenty of fermented foods like yogurt, kefir, kimchi, kombucha and fermented vegetables showed more diverse gut bacteria. Levels of 19 inflammatory proteins in their blood also dropped.
A high-fiber-only diet did not shift either marker in that same trial over 10 weeks. Fermented foods appeared to do the heavier lifting on diversity in the short term.
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This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.