Globally, 165 million children are stunted or short for their age, while in Bangladesh -- where the researchers have been working -- stunting affects 36 percent of children under 5. Being stunted increases the chance of both cognitive disability and death before the age of 5.

One possible factor contributing to stunting is damage to the gut - "environmental enteropathy" - leading to inflammation and poor uptake of dietary nutrients. The origins of environmental enteropathy are not clear, but excessive numbers of bacteria in the small intestine, referred to as small intestine bacterial overgrowth (SIBO), have been suggested as one possible cause.

To explore this idea, the researchers examined 103 2-year-old children who had been followed from birth in an urban slum in Mirpur, Dhaka. Despite vaccination, medical care, nutritional counseling and care, stunting increased in these infants from 9.5 percent at birth to 27.6 percent at 1 year of age.

Notably, one in six 2-year-old children tested showed signs of SIBO, as revealed by the presence of hydrogen in their breath, a result of bacterial metabolism of sugar to hydrogen in the small intestine. Importantly, bacterial overgrowth was more common in children showing stunted growth and was associated with gut inflammation.

"We knew that the children's intestines were being damaged and that was associated with malnutrition, so we decided to test to see if this damage could be due in part to bacteria in their small intestine," said lead author on the study. 

http://mbio.asm.org/content/7/1/e02102-15.full