Babies who start on solid foods at or before three months of age may experience changes in their levels of gut bacteria, according to a new study.
Prior studies have linked the early introduction of solid foods to a higher chance of being overweight in childhood.
The new study suggests that introducing solid foods early on may alter a baby’s gut bacteria population which in turn can predispose infants to being overweight later.
“How the early introduction of solid foods would cause the later development of obesity has been unknown, but our findings suggest that disruptions to gut bacteria may be one explanation,” says Noel Mueller, assistant professor in the epidemiology department at the Bloomberg School at Johns Hopkins University.
Pediatricians’ associations typically recommend that infants only consume breast milk for the first four to six months. After that, parents should introduce solid foods as a supplement to breastmilk or milk formula.
Prior studies also indicate that the timing of solid food introduction may affect the chances of developing eczema, food allergies, asthma, hay fever, and other allergy-related conditions.
To understand better how the timing of introducing solid food, in terms of biological mechanisms, could affect a child’s metabolic and/or immune health, Mueller and colleagues analyzed data from the Nurture study, which tracked infants in a community in Durham, North Carolina for the first year of life. Researchers mainly conducted that study to explore early-life factors that might predispose children to obesity.
The scientists interviewed mothers every three months about the infants’ diets and other factors and also collected stool samples from the infants.
The new analysis included data from 67 children, for which the researchers compared the timing of solid food introduction with the bacterial species and byproducts found in the month-3 and month-12 stool samples.
The findings show that stool samples from infants who had started on solid foods at or before three months, at the month-3 time point, and even at the month-12 time point, contained a significantly higher diversity of bacteria, indicating a more diverse gut bacterial population or “microbiome,” compared to samples from infants who had started later on solid foods.
The finding is consistent with a 2018 Norwegian-led study, which linked higher gut microbiome diversity at 3 months of age to a greater chance of being overweight later in childhood.
The researchers also measured the stool-sample levels of organic bacterial byproducts called short-chain fatty acids. Prior studies have linked higher stool levels of butyric acid and other short-chain fatty acids in adults to increased risks of obesity, diabetes, and hypertension.
The new study showed that infants starting on solid foods by three months had significantly higher concentrations of butyric acid, as well as total short-chain fatty acids, at 12 months—but not at 3 months, which could indicate a delayed and sustained impact of early solid-food introduction.
On the whole, the findings are consistent with the emerging evidence that gut microbiome changes are key factors in the development of common metabolic and immune conditions, Mueller says, and suggest that scientists are on the right track in studying these changes.
Researchers need to do further study to determine if these measures of microbiome diversity and short-chain fatty acid concentration truly drive the development of obesity and other disorders, he says.
Mueller and colleagues are continuing to conduct studies of diet and the gut microbiome in infants and children, and the associations between these factors and outcomes such as obesity and immune-related disorders.
The study appears in BMC Microbiology. The National Institutes of Health funded the work.
Source: Johns Hopkins University
