Household disinfectants may be making children overweight, scientists find

Toddlers exposed to bacteria-killing products more susceptible to obesity as gut organisms altered, study suggests

Everyday disinfectants and surface cleaners could be making children overweight by altering the bacteria in their guts, a new study suggests.

Babies exposed to household disinfectants have a higher body mass index (BMI) at the age of three, while excess weight is less common in toddlers from homes that clean with eco-friendly products, researchers have found.

Although the scientists warned that no causal link had been proven, they said the results suggested gut microorganisms were “the culprit” in the link between disinfectant use and children becoming overweight.

The Canadian experts took samples from 757 infants for their study, during which they followed participants as they grew from the womb, into childhood and adolescence.

Babies from homes where antimicrobial disinfectants were used at least once a week were twice as likely to have higher levels of a bacteria linked with obesity when they were three or four months old than those whose families did not frequently use disinfectants, the study found.

When the children with higher levels of the bacteria Lachnospiraceae were three years old, their BMI was higher than that of their peers, according to the report in the Canadian Medical Association Journal.

Higher levels of Lachnospiraceae are linked with higher body fat and insulin resistance, although it is normal to find them in the gut, said Anita Kozyrskyj, senior author of the study.

The human gut hosts tens of trillions of microorganisms, including an estimated 1,000 species of bacteria.

The researchers did not find any links between obesity and the use of washing detergents that did not contain bacteria-killing ingredients such as bleach and hydrogen peroxide.

Ms Kozyrskyj, a paediatrics professor at the University of Alberta, said the results suggested that gut microbiota – groups of microorganisms – were the culprit in the association between disinfectant use and becoming overweight.

Past research has drawn a connection between gut microbiota composition and weight in adulthood.

Piglets born indoors and raised in conditions where disinfectant aerosols are frequently used have perturbed gut microbial balances compared with those not reared under such conditions, the scientists noted.

They said babies living in households that used eco-friendly cleaners had different microbiota and were less likely to be overweight as toddlers.

“The eco-friendly product-using mothers may be more healthy,” the professor said, adding that the mother’s overall healthier lifestyle and eating habits may benefit both the gut bacteria and their children’s weight.

It is possible that some disinfectant products contained triclosan, which is no longer used in UK cleaning products

Sally Bloomfield

Ms Kozyrskyj said she could not recommend buying eco-friendly products as a direct result of the study, since a causal link had not been confirmed, but she said the findings had opened her mind to using green products such as homemade vinegar cleaners in her own home.

Sally Bloomfield, honorary professor at the London School of Hygiene and Tropical Medicine, said more questions needed answers before conclusions could be drawn.

“This study must be regarded as only a preliminary indication that disinfectant use might be a contributory factor to reducing gut microbe diversity, alongside factors such as c-section birth, overuse of antibiotics etc," she said.

"A major flaw is the non-homogenous nature of the products in each category. In some cases, the commercial products were categorised into disinfectants or detergents without detailed knowledge of ingredients."

It is likely that the chemical nature of the microbiocidal and other ingredients of the products would have varied significantly, she said.

"To draw any real conclusions, answers are needed to questions such as 'what biocides were in the products and where were products used?' It is possible that some disinfectant products contained triclosan, which is no longer used in UK cleaning products."

She added that it must be remembered that failure to use disinfectants when there is significant risk is linked with increased risk of the spread of infection.