Restoring healthy gut bacteria could help starving children

Feeding severely malnourished infants a diet rich in bananas, chickpeas and peanuts may boost healthy gut bacteria and help children grow, according to two studies published on 12 July in Science (1, 2).

Around 150 million children are malnourished across the globe, according to the World Health Organization (WHO). And these starving children often don’t recover even after they do get enough to eat. Years later, the brains of impoverished children remain underdeveloped and they are also more susceptible to disease.

The microbiome is made up of billions of different bacteria species and has become increasingly recognised as an important indicator of health and disease — which seems reasonable considering bacteria make up more than 50 per cent of the total cells in the human body. Moreover, gut bacteria have been linked to allergies, obesity, neurodegenerative diseases like Parkinson’s, depression, and other widespread diseases affecting humans.

So, the researchers, led by Prof Jeffrey Gordon from Washington University in collaboration with Tahmeed Ahmed, director of nutrition research at the International Centre for Diarrhoeal Disease Research in Dhaka Bangladesh, set out to determine the cause of this poor growth in severely malnourished children by looking more closely at their gut bacteria. Knowing the role the microbiome plays in obesity, Gordon and Ahmed wondered whether it may play a similar role in malnutrition.

In 2014, they published a paper showing that the microbiome of an infant normally evolves as children grow. However, the same is not true for severely malnourished children, in which the gut remains dominated by bacteria found in younger healthy children.

Another later study in mice showed that perhaps a “mature” microbiome is needed for proper growth and development, as mice with the microbiomes of younger children developed less muscle and bones, and appeared to also have an impaired metabolism.

So, this time the team identified 15 different types of bacteria that either increase or decrease as the microbiome matures in healthy infants from Bangladesh, Peru, and India. Then, looked at which foods could promote or suppress certain gut bacteria.

Most of the research was carried out in animals, but one of the studies tested the different diets on 60 children in Bangladesh over a one-month period. Although the study period was too short to determine long-term physical recovery, they were able to detect molecular changes in the blood associated with the microbiome.

Interestingly, they discovered that a diet of bananas, soy, peanut flour, and chickpeas promotes microbes linked to bone growth, brain development, and immune function. But as it turns out, milk powder and rice — both typical ingredients in food aid — did not promote a mature microbiome. And a diet dominated by rice or lentils may even damage the gut, in some cases.

So, what are the next steps? The authors are still unsure why some foods are better than others. And researchers also now recognise the diversity of microbiomes around the globe. This means the same diet may not be suitable for children in Africa or South America, for example. A larger trial is now underway to look at the long-term effects — over 3 months — of certain diets.

The results highlight the importance of selecting the right nutrients to nourish the gut microbiome of infants. And while not necessarily a ‘cure-all,’ the findings are intriguing and could help improve the nutrition of undernourished and well-fed children alike — a poor diet during childhood increases the risk of obesity and diabetes and can trigger life-long health issues.

(1) Gehrig, J.L. et al.Effects of microbiota-directed foods in gnotobiotic animals and undernourished children. Science (2019). DOI: 10.1126/science.aau4732

(2) Raman, A.S. et al. A sparse covarying unit that describes healthy and impaired human gut microbiota development. Science (2019). DOI: 10.1126/science.aau4735