Breastfeeding may help reduce the impact of socioeconomic pressures on babies’ gut health and later childhood outcomes, according to a new analysis.
Researchers found that breastfeeding was linked to lower odds of asthma, excess weight and behavioural problems by the age of five among children from families with fewer resources.
The study, published in Cell Reports Medicine, analysed data from 2,752 families taking part in the Canadian CHILD Cohort Study, which follows families from pregnancy into childhood.
Researchers also examined infant stool samples to understand how early gut bacteria may be connected to family resources, feeding patterns and later health.
The same pattern was observed in a separate Danish cohort of 681 children, strengthening the findings across different countries and healthcare systems.
The researchers stressed that breastfeeding should not be viewed as a cure-all, but said the findings suggest the infant gut microbiome may be one route through which social and environmental pressures affect later health.
Dr Darlene L.Y. Dai, a biostatistician at BC Children’s Hospital Research Institute, led the analysis.
Across 36 conditions before and soon after birth, family resources were linked with a range of early exposures, including feeding, home conditions, parental health and neighbourhood factors.
Babies from higher-resource families had different gut microbiome patterns by three months of age, and those differences remained visible at one year.
By age five, higher family resources were also linked with lower odds of asthma, overweight or obesity, and emotional or behavioural challenges.
Breastfeeding appeared to reduce the influence of some early exposures on the gut microbiome.
Among babies who were not breastfed at three months, 20 perinatal factors were associated with microbiome composition. Among breastfed babies, only three were.
The researchers said this suggests breast milk may help stabilise the microbial community in early life.
Dai said: “Breastfeeding seemed to act as a shield, protecting the infant microbiota across many different exposures.”
Among children from lower-resource families, exclusive breastfeeding for six months was associated with 40 per cent lower odds of at least one adverse outcome by age five.
The outcomes examined included asthma, overweight or obesity, and emotional or behavioural problems.
World health groups recommend exclusive breastfeeding for around the first six months when possible and safe.
The study also highlighted the potential role of Bifidobacterium infantis, a bacterium adapted to the breastfed infant gut.
The bacterium helps digest complex milk sugars that babies cannot break down themselves, supporting healthier gut conditions.
Dai described B. infantis as “a microbial powerhouse”.
In the Canadian data, the bacterium was linked with protection against three of the four outcomes studied, including asthma, overweight or obesity, and allergic sensitisation.
However, researchers found the species was relatively uncommon. B. infantis was detected in only 25 per cent of Canadian children during the first year, despite most having some breastfeeding.
City-level patterns suggested that breast milk alone may not determine whether babies acquire the bacterium, with higher prevalence seen in Vancouver and Toronto than in Winnipeg and Edmonton among breastfed infants.
The researchers said this points to the wider role of households, communities and everyday environments in shaping the infant microbiome.
The findings were also tested in a Danish cohort, where higher family resources were similarly linked with lower asthma and behavioural risks.
Among lower-resource Danish children, exclusive breastfeeding for four months was associated with 49 per cent lower odds of adverse outcomes.
The authors said the findings should not be interpreted as placing responsibility on individual mothers.
Breastfeeding can be shaped by work schedules, paid leave, delivery care, lactation support, illness, stress and family history.
In the Canadian cohort, breastfeeding rates were higher among the highest-resource families than the lowest-resource families at both three months and one year.
The researchers said this highlights the importance of social and healthcare support, rather than blaming parents for circumstances that may make breastfeeding difficult or impossible.
As an observational study, the research cannot prove that breastfeeding directly caused all later health differences.
The authors also noted that formula feeding can be necessary, and that families should receive medical guidance when breastfeeding is painful, unsafe, unavailable or insufficient.
They said stronger parental leave policies, lactation care, donor milk programmes and further research into restoring helpful microbes could help make early-life health benefits less dependent on family income.