Gut Bacteria Reflect Dietary Differences

High-fiber, low-fat diets cultivate healthier intestinal microbes, study suggests.

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By Gwyneth Dickey, Science News

A termite a day may keep the doctor away. African children who eat a high-fiber diet (and the occasional wood-digesting insect) have gut bacteria that help them digest plant fibers and protect them from diarrhea and inflammatory disease, a new study finds. The research may lead to new probiotics that improve the digestive health of Westerners, who were found to have a less diverse assemblage of intestinal microbes.

“This discovery is very important because it bears on how we should feed our children to make them healthy,” says study coauthor Duccio Cavalieri, a microbiologist at the University of Florence in Italy. “We should move our habits toward a diet more heavy in fiber, with the same amount of calories.”

Animals have bacteria in their guts to help digest their food, train their immune systems and protect them from harmful bacteria. Different types of food encourage different abundances and diversity of bacteria to grow in the gut.

Some scientists have hypothesized that improved sanitation in Western developed countries has decreased people’s microbe exposure and has led to autoimmune disorders, inflammatory bowel disease and allergies.

So Cavalieri and a team of scientists compared the gut microbes of children from Burkina Faso and Italy. Children in rural Burkina Faso eat foods similar to those that people ate 10,000 years ago when farming was first developed. Their diet is high in fiber, cereals, non-animal protein and plants. European children, on the other hand, eat foods typical of a Western diet, high in animal protein, sugar and fat, and low in fiber.

In the new study, researchers used DNA sequencing to identify bacteria in the guts of 30 healthy, normally growing children ages 1 to 6 from these two populations.

Breast-fed children from the two groups had similar gut bacteria, likely because the children were eating the same food. But when children started to eat culturally distinct solid foods, the gut microflora of the two groups started to look different. The results are published online August 2 in the Proceedings of the National Academy of Sciences.

Children from Burkina Faso, who ate millet grain, sorghum wheat, legumes and vegetables, had high numbers of bacteria that digest plant fibers. Also found in the guts of termites, these bacteria break down fibers that humans typically can’t. The bacteria make short-chain fatty acids that give people energy and protect them from inflammatory gut diseases such as Crohn’s disease and inflammatory bowel disorder.

Burkina Faso's children also had decreased numbers of diarrhea-causing bacteria compared with children from Italy. That finding surprised the team, because the African children often drank water polluted with such bacteria.

“The notion that gut flora plays a role in human health has been marginally ignored,” says evolutionary nutritionist Loren Cordain of Colorado State University in Fort Collins, who was not involved with this study. “What we’ve found over the past five or 10 years is that it plays a huge role in our health and well being.”

Compared with the European children, African children’s gut bacteria were more diverse, which would enable them to adapt to different diets more easily, the authors report. These children not only had more of the good bacteria, but they also had unique bacterial strains that weren’t found in European children.

“We have probably lost many of the species that these children still have,” says Cavalieri. “We should somehow discover what is out there and discover what we might have lost.”

Children in Burkina Faso likely got many of their healthy digestive bacteria from their mothers’ birth canals and skin, as well as from their environment, such as from the termites they sometimes eat.

“We’re not saying you should eat termites,” Cavalieri says. But, he says, people could get those healthy gut bacteria from new probiotic pills that could be developed in the future.

It’s hard to change people’s DNA to prevent disease, Cavalieri says, but researchers may instead be able to act on the body’s bacteria.