Statistics Canada says that almost a third of Canadian children and teenagers are overweight or obese. Eating too much and exercising too little are two risk factors behind the increase. But a study published earlier today in the Canadian Medical Association Journal zeros on a strange new culprit who lies in wait in your house. And no, it's not the fridge.
The risk factor is exposure to daily household cleaners. Researchers from across Canada have looked at data from the Canadian study on the development of healthy babies in the longitudinal direction (CHILD). It is a long-term study of 3,500 children with the aim to predict, prevent and treat chronic diseases. The researchers compared babies of three to four months old who lived in households where consumer disinfectants were used once a week for infants living in homes where disinfectants were used far less often. Then they watched these children again at the age of three.
What they found is that children who lived in households where disinfectants were used once a week had a higher body mass index (BMI). In other words, they were more likely to be overweight or obese.
At first glance this is a main scratcher. Household disinfectants kill germs that live on surfaces in the baby's environment. The researchers assume that the proximity of these cleaning agents has an impact on the bacteria in the environment and also in the intestines of the baby.
This is how: the researchers not only measured the BMI of the baby, they also checked the baby's droppings for bacteria and made a very interesting discovery. Infants of three to four months who lived in homes where multi-surface cleaning agents were used had lower levels Haemophilus and Clostridium bacteria and higher levels of a so-called germ Lachnospiraceae. The more often the household uses cleaning agents, the higher the level Lachnospiraceae.
The germ hypothesis of obesity
But what do bacteria have to do with being overweight or obese? For some time now, researchers have been studying a possible link between obesity and the presence of certain bacteria in your intestines. Bacteria in our intestines are made from hundreds of genes. Those genes produce amino acids that can be measured in the bloodstream. The germ hypothesis of obesity is that these amino acids influence metabolism and cause some people to arrive. Therefore, anything we eat or that we are exposed to in the environment that affects bacteria in the gut can affect our metabolism and cause us to arrive, or perhaps even lose weight. For more information, here is a good summary.
A comment published in CMAJ referred to the findings as plausible. Researchers at Johns Hopkins Bloomberg School of Public Health said that exposure to germs during childhood seems to be important for the development of the immune system and to program the body's metabolism. Previous studies found a higher incidence of obesity in piglets living in an often disinfected environment.
Studies have also been conducted in humans. Babies born with a caesarean section are more likely to grow heavy or obese than those born vaginally. Babies who pass through the birth canal take up germs that babies born with caesarean sections are missing.
Other studies have shown that frequent use of household disinfectants reduces bacteria indoors.
The comment adds that it is plausible that tensions from Lachnospiraceae play a role in metabolic pathways that lead to obesity. Researchers look at the role that gut bacteria play in a wide range of other conditions, including bladder infections, kidney stones, Crohn's disease, colitis, diabetes, heart disease, fatty liver, alcoholic cirrhosis and even liver cancer.
More research needed for implementation
There are reasons to be somewhat skeptical about the findings. Statistically, the results were considered to be marginally significant. The researchers were unable to classify cleaning products based on their actual ingredients. The authors of the study admit that this is an important limitation of the study. Without knowing the cleaning agents, it is difficult to establish an exact mechanism of action. The researchers acknowledge that the study was limited by not knowing factors in the mother's own medical history that could have influenced the weight of the baby. These include her BMI, smoking history and educational level.
Much more research is needed before one of these is converted into practical advice. Yet the study had one tempting finding that you might want to take action now. Babies who grew up in households using environmentally friendly cleaning products were not overweight or obese at the age of three. They also had different bacteria in their intestines. They had much lower levels of a bacterium called Enterobacteriaceae. There is no evidence that certain bacteria have a direct effect on the risk of obesity.
The researchers are not sure why these children have not become too heavy. It is possible that babies who grew up in households using environmentally friendly products have a healthier lifestyle and healthier mothers. It is not harmful to use environmentally friendly cleaning products and to make the healthiest lifestyle possible. But there may not be a specific advantage.