Western diets rich in fat and sugar are harming the health of children in industrialised countries by affecting their gut bacteria, new research suggests.
Scientists who compared groups of children aged one to six in Italy and rural Africa found striking differences in the composition of bug populations inhabiting their digestive systems.
They claim the reason is their different diets -- and argue that this could explain why "western" children are so prone to problems such as obesity and allergies. The African children from Burkina Faso had a lower proportion of microbes associated with obesity in adults, and higher numbers of bugs linked to leanness.
Other types of bacteria found in the guts of African, but not Italian, children assisted the digestion of plant foods. These bugs generated fatty acids that are known to protect against inflammation, and may help to prevent the over-active immune reactions that lead to allergies.
African children had fewer of the bacteria that cause common stomach upsets and diarrhoea, such as Shigella and Escherichia, the E.coli bug.
While the African children ate a diet consisting mainly of cereals, pulses and vegetables, their Italian counterparts consumed much higher amounts of meat, fat and sugar. Overall, the African children had a far more diverse population of bacteria in the faecal samples analysed. The scientists, led by Dr Paolo Lionetti, reported their findings in the journal Proceedings of the National Academy of Sciences.
They wrote: "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.
"We can hypothesise that the reduction in richness we observe in EU (European) compared with BF (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."
They added: "Increased gut microbial diversity and reduced quantities of potentially pathogenic (harmful) strains in BF would agree with the 'old friend' hypothesis, indicating a role of microbiota in protecting children from pathogens as well as from gastrointestinal diseases."
The mainly vegetarian diet of the African children resembled that consumed by humans shortly after the birth of agriculture, said the scientists.