Household disinfectants seem like such a good idea, especially when you have children — after all, children make messes, and killing germs helps keep children healthy, right? Not always, it turns out. Sometimes germs actually keep us healthy and keep us at a healthy weight.

More and more, we are learning that not all bacteria are bad. In fact, the bacteria that live naturally in and on our bodies, especially in our digestive tracts, are crucial for health. When we mess with those bacteria, it increases the risk of many problems, including cardiovascular disease, diabetes, rheumatoid arthritis, inflammatory bowel disease, cancer — and obesity.

Researchers from Canada used data from the Canadian Healthy Infant Longitudinal Development (CHILD) study to see if there was a connection between the use of household disinfectants by mothers and the weight of their children. They found that indeed, when mothers used household disinfectants (most commonly multi-surface cleaners, hand soap, and spray air fresheners), their children were more likely to be overweight or obese at age 3. By looking at stool samples from the children when they were infants, they found that this increased risk seemed to be related to a change in the bacteria in the digestive tract. The children whose mothers used disinfectants had less of the “healthier” bacteria.

When families use disinfectants, there are fewer bacteria in the house, obviously. Since children spend most of their life indoors, this means that those in “disinfected” homes are exposed to fewer bacteria, and have less of a chance to grow the bacteria that should ideally be living throughout the digestive tract, from mouth to rectum. Interestingly, a study of the bacteria in the mouths of two-year-olds showed that certain mixes of bacteria types increase the risk of rapid weight gain.

It’s not just household disinfectants that affect the bacteria in our bodies. Antibiotics and antacids can too, as well as our diet and lifestyle.

And obviously, it’s not just bacteria that affect weight gain. Interestingly, in the Canadian study children of mothers who used eco-friendly cleaning products were less likely to be overweight at 3 — but this lower risk did not appear to be related to the bacteria in their stool. Instead, the researchers said, it was more likely related to the fact that the mothers in the study who used eco-friendly cleaning products were more likely to breastfeed and to have more education, and less likely to be overweight themselves. Breastfeeding, maternal education, and maternal weight are factors that are known to affect the weight of children.

Given what we know, though, about the many problems that can occur when we get too aggressive about killing bacteria, it’s not a bad idea to rethink our cleaning products. Here are some ideas:

Avoid anything that says “antibacterial” on the label.

Look for natural cleaning products. Not only are they less likely to kill healthy bacteria, they have fewer dangerous chemicals. The Environmental Working Group has a useful guide to healthy cleaning.

Wash your hands — and your children’s hands — with plain old soap and water.

Consider making your own cleaning products, with things like vinegar, baking soda, lemon juice — and that plain old soap. There are lots of websites with recipes for inexpensive, effective, safe, and bacteria-sparing cleaning products.

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