Gut bacteria respect diets, not borders

DIET DIVIDES  People in Malawi and Venezuela have similar microbes in their guts even though they live on opposite sides of the world. Indigenous Venezuelans’ microbiome has much more diversity than Americans', research shows. 


They live on opposite sides of the planet, but people in Malawi and Venezuela have similar microbes in their guts. Americans, on the other hand, have a distinctive microbiome with about 25 percent less diversity than indigenous Venezuelans’.

It comes down largely to diet, researchers determined after comparing more than 500 people from rural Malawi, the United States and the Guahibo society in Venezuela. Malawian and Guahibo diets are rich in corn and cassava, with meat an occasional treat. Gut microbes of the three groups reflected that, the team reported in 2012. Overall, Malawian and Guahibo gut microbiomes resembled those of herbivorous mammals, while American guts were more similar to carnivores’.

A more recent study found that major diet shifts can change the mix of gut microbes noticeably in just a day. Omnivores switching to a diet of all animal products saw the biggest change, as some bacteria boomed and others declined. Microbes settled back to their previous profiles a day or two after subjects returned to their usual diets, researchers report December 11 in Nature.

UNITED STATES Americans eat more meat than anyone else in the world except Luxembourgers, more than 120 kilograms per person annually. Other widely consumed foods include: bread, lettuce and tomatoes, potatoes, pasta, milk and dairy products. USDA/Jon Sullivan, Wikimedia Commons

VENEZUELA Indigenous Guahibo people only occasionally eat meat, so a meal including stewed fish (on plate, left) might constitute a special occasion. The Guahibo diet is high in starch, and processed foods are not unknown. Some typical foods: corn arepas (shown, bottom), cassava, sugar, cheese. T. Yatsunenko et al/Nature 2012/Wilfredor/Wikimedia Commons

Malawai Meals here are also heavy on starch. One staple is cornmeal porridge or cakes (center) eaten with ndiwo (top left), a sauce or relish made with beans, meat or vegetables. Among the most frequently eaten Malawian dishes: cornmeal porridge or cake, leafy greens, matemba, a small fish, pigeon peas, pumpkin leaves. T. Yatsunenko et al/Nature 2012/Geoff Gallice/Flickr

GUT BACTERIA Americans and others with high-protein fatty diets have guts loaded with Bacteroides bacteria, which can withstand bile produced after eating fat. Prevotella bacteria, which help digest fiber, are more dominant in the guts of people on low-meat, grain-based diets. T. Yatsunenko et al/Nature 2012

Erika Engelhaupt is a freelance science writer and editor based in Knoxville, Tenn.

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