Germs living in the gut may cause higher rates of allergies, chronic stomach upsets and even obesity among children living in rich industrialised countries, researchers reported.
They compared intestinal bacteria between European Union children and young villagers in remote Burkina Faso, and found enough differences to help explain disparities in chronic disease and obesity.
The findings, published in the Proceedings of the National Academy of Sciences, may support the development of probiotic products to help restore the ancient balance and keep humans leaner and healthier, the researchers said.
"Our results suggest that diet has a dominant role over other possible variables such as ethnicity, sanitation, hygiene, geography, and climate, in shaping the gut microbiota," Paolo Lionetti of the University of Florence in Italy and colleagues wrote.
"We can hypothesize that the reduction in richness we observe in EU compared with Burkina Faso children, could indicate how the consumption of sugar, animal fat, and calorie-dense foods in industrialised countries is rapidly limiting the adaptive potential of the microbiota."
The study builds on a body of evidence that human health relies heavily on the trillions of micro-organisms living in and on our bodies. Only a fraction cause disease directly - many more help digest food, affect other bacteria and may influence hundreds of biological functions.
Several recent studies have found that certain bacteria cause inflammation that can affect appetite as well as inflammatory bowel conditions like Crohn's disease and colitis, including a study published in Science in March.
Trading one disease for another
"Western developed countries successfully controlled infectious diseases during the second half of the last century, by improving sanitation and using antibiotics and vaccines," the researchers wrote.
"At the same time, a rise in new diseases such as allergic, autoimmune disorders, and inflammatory bowel disease both in adults and in children has been observed," they added.
Lionetti's team studied the DNA of the gut bacteria of children in Burkina Faso, who are breast-fed up to age two and eat a diet likely similar to stone-age humans, rich in whole grains such as millet, legumes such as black-eyed peas, and vegetables. They eat very little meat.
The Western diet, in contrast, is heavy in meat, processed grains, sugar and fat.
The Italian team found the African children had many bacteria that help break down fibre, but the European children were lacking these microbes. The ratios were similar to studies comparing the gut bacteria of lean people to obese people.
This bacterial balance could even be causing obesity, the researchers said. It may also be useful to test children for these bacteria to see if they are at high risk of becoming obese, they said.
"Reduction in microbial richness is possibly one of the undesirable effects of globalisation and of eating generic, nutrient-rich, uncontaminated foods," Lionetti's team wrote in the study. (Reuters Health – 3 August 2010)