Each year, the United States sends over 30 million tons of food aid to nearly 50 million people facing starvation across the world. This food aid is usually comprised of common staples like flour, bread, powdered milk, and beans, and is intended to nourish especially the youngest victims of hunger, whose growth and development are often stunted by the lack of nutrients. However, a pair of recent studies suggested that the effectiveness of this aid may be impeded by an unexpected factor: bacteria.

These aren’t the kinds of bacteria that cause disease or infections. Instead, they are normal residents of human bodies, composing a person’s “microbiome” and working cooperatively with their human host to produce and consume various molecules that pass through their body. These bacteria have been implicated in everything from weight to mood. Previous research has shown that when children are malnourished, their microbiomes don’t develop properly and instead resemble those of younger children.

In the first study, researchers wanted to track the abundance of different strains of bacteria in healthy children’s microbiomes as they grow. These bacteria were detected by collecting genetic material collected from the children’s stool samples over the first 5 years of life, and matching it to genes found in specific strains of bacteria. They found a set of 15 bacteria whose abundance fluctuated in a coordinated manner in healthy children, and even in healthy piglets. This seemed, to the researchers, to be a bacterial signature of normal development. Therefore, helping children recover from starvation might require returning these bacteria to normal too.

This naturally sparked another question: How can we foster normal bacterial growth patterns within starved children? In a parallel study, researchers transplanted bacteria from a malnourished child into a mouse to make its microbiome look more like one that would result after starvation. Then, they fed these mice a wide variety of foods and identified the foods that sparked the recovery of age-appropriate bacterial strains. This included items like bananas and chickpeas, which were correlated with more bacterial strains that are expected later in development. Foods that are more commonly included in food aid and fed to malnourished children—like rice, milk powder, and eggs—did not seem to have the same effect.

To test whether these foods could actually restore a properly-developed microbiome in a child, they tested a new 18-ingredient diet in both mice and piglets who had microbiome transplants from malnourished children, as well as in such children themselves. They found that the animals who received the special diet had improved weight gain, but they didn’t observe the same in the kids. However, the children who received the special diet did have healthier level of various molecules in their blood, which is also a crucial component of recovery.

So, are well-intentioned crates of rice and powdered milk useless? Not quite — they’re still important components of rebuilding these children’s strength. But alone, they might not enable lasting, comprehensive improvements in health. Instead, these children may be better served by supplementing their diets with a few items tailored to their bacterial inhabitants.

Managing Correspondent: Aparna Nathan

Original articles: A sparse covarying unit that describes healthy and impaired human gut microbiota development – Science

Effects of microbiota-directed foods in gnotobiotic animals and undernourished children – Science

Media coverage: A Mix Of These Foods Could Restore Healthy Microbes In Malnourished Kids – NPR

Scientists Made a Microbe-Boosting Diet to Help Malnourished Kids Grow – New York Times

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