Missing gut bacteria linked to poor nutrition in children

Children with malnutrition might be missing the right mix of germs.

Three new studies suggest that certain bacteria in the gut may be vital for healthy growth. They also might help kids bounce back from malnutrition. The studies were reported February 18.

Malnutrition occurs when the body gets too few calories or lacks the right mix of nutrients. In children, it can severely stunt growth and affect whether they develop normally. Each year, malnutrition plays a role in the deaths of more than one million children. Those who survive may be shorter, face delayed development of their brains and suffer problems with their immune systems. Even after these kids start to get enough food, many will never fully recover.

“Everyone’s been kind of puzzled about why,” says biologist Brett Finlay. Finlay works at the University of British Columbia and was not involved in the new research. “People used to think if you just fed the kids they’d be fine,” Finlay says. “But that didn’t work.”

Instead, certain gut microbes might be needed to protect children who are suffering from poor diets. “It’s extremely exciting,” Finley says. “We know what causes malnutrition. And maybe now we can do something to fix it.”

Studies tease out the germs’ importance

Scientists had previously seen several hints that microbes might be important to child health. Still, no one knew whether bacteria could actually treat malnutrition nor which microbes might help.

To figure this out, biologist François Leulier and his colleagues fed a diet low in protein to baby mice. Some had bacteria in their guts, others didn’t. Then they measured how rodents’ developed from infancy through adulthood.

Big differences emerged in how the young animals grew, says Leulier. He works at the Institute of Functional Genomics of Lyon in France. Mice without gut bacteria were small and stunted. Those mice with gut microbes were bigger by every measure. They had bigger bones, organs and bodies. The gut microbes helped mice grow by increasing production of a compound known as IGF-1, the team showed. This is a hormone that directs growth. And one microbe in particular, Lactobacillus plantarum (LAK-tow-ba-sill-us Plan-TAAR-um) , was particularly helpful.

Many species of microbes come in slightly different forms, or strains. The L. plantarum strain that was so helpful is called strain WJL.

Leulier’s team described its findings in Science.

Leulier hopes that this strain’s growth-boosting effects might one day help treat malnourished children. But that day is still a long way off, he adds.  “We can envision some therapy solutions,” he says, but scientists are still trying to understand the basic science behind the effects.

Another study in the same issue of Science found two more potentially helpful microbes. Jeffrey Gordon is a physician and microbiologist at George Washington University in St. Louis, Mo. He was part of team that looked at gut bacteria in healthy and malnourished babies in the African country of Malawi.

The researchers knew that kids of similar ages usually have similar gut bacteria. But these malnourished babies had a microbial mix that looked more like that of very young infants than healthy babies of their own age. (The researchers had previously seen similar results in malnourished children in Bangladesh.) Gordon now believes the mix of microbes — or microbiomes — in these kids may be a sign of poor nutrition. Indeed, that could be part of why the kids were so sick.

Germ therapy

Gordon and his team wanted to better understand the problem. So they took bacteria from both malnourished and healthy children. Then they transplanted these germs into mice. Those getting bacteria from malnourished kids didn’t grow as well as did mice receiving gut microbes from healthy children. Adding back just two species of bacteria helped the runty mice begin to grow again.

Those germs have very long names: Ruminococcus gnavus and Clostridium symbiosum. But learning the names may be worthwhile, Gordon says. These mouse data hint at a potential treatment for malnourished children. .

“It’s the first step in the journey,” he says. And it’s one he hopes will lead to foods that nurture healthy microbiomes.

His team has already had some success. In a study published in Cell, Gordon’s team analyzed breast milk of Malawian women who had either healthy or stunted infants. The breast milk of mothers with healthy babies was special — full of carbohydrates containing a chemical called sialic (Sy-AAL-ik) acid.

The researchers wanted to test whether these carbs boost growth. But it would require a lot of breast milk to get enough of the carbohydrates for testing, Gordon says. So his group turned to a cheese company in California. It was making similar carbohydrates from whey. Whey is a by-product that’s created when cheese is made from cow’s milk. Gordon’s team gave the whey-based carbs to baby mice and piglets with bad gut microbes. And it helped. It boosted the animals’ growth.

Together, these three new studies show that microbes’ are important to human development, Gordon says.

Finlay agrees. “We know microbes play a major role in obesity, but this really confirms their role in malnutrition,” he says.

Power Words

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bacterium (plural bacteria)    A single-celled organism. These dwell nearly everywhere on Earth, from the bottom of the sea to inside animals.

carbohydrates    Any of a large group of compounds occurring in foods and living tissues, including sugars, starch and cellulose. They contain hydrogen and oxygen in the same ratio as water (2:1) and typically can be broken down to release energy in the animal body.

development  (in biology) The growth of an organism from conception through adulthood, often undergoing changes in chemistry, size and sometimes even shape.

genome   The complete set of genes or genetic material in a cell or an organism. The study of this genetic inheritance housed within cells is known as genomics.

gut Colloquial term for an organism’s stomach and/or intestines. It is where food is broken down and absorbed for use by the rest of the body.

hormone   (in zoology and medicine)  A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. 

immune system The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.

malnutrition     (adj. malnourished) A condition that develops when an individual gets too little energy (calories) and/or not enough of the proper nutrients to support growth and health. Malnutrition can lead to stunted growth and susceptibility to disease.

microbe    Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

microbiota  The microorganisms that live in a particular place or geological period. Scientists call the entirety of the microorganisms in a human or other animal its microbiome.

nutrient  A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.

proteins     Compounds made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. The hemoglobin in blood and the antibodies that attempt to fight infections are among the better-known, stand-alone proteins.Medicines frequently work by latching onto proteins.

sialic acid       A family of 43 naturally occurring compounds made from a nine-carbon sugar, known as neuraminic acid. Cells in higher animals build up these compounds, starting with the simple sugar glucose. The body uses these compounds especially in the nervous system.

strain  (in biology) Organisms that belong to the same species that share some small but definable characteristics. For example, biologists breed certain strains of mice that may have a particular susceptibility to disease. Certain bacteria or viruses may develop one or more mutations that turn them into a strain that is immune to the ordinarily lethal effect of one or more drugs.

whey    The liquid left behind during cheese making after milk proteins have solidified into curdles. Whey is also a type of milk protein that can be consumed as a dietary supplement.