When it comes to the health of our kids, a little dirt can do wonders

“Invisible friends in the soils, plants, and air provide critical roles in regulating our immune systems and many other functions in our bodies,” explains Dr Jake Robinson, a microbial ecologist at Flinders University and author of new book Invisible Friends: How Microbes Shape Our Lives and the World Around Us. “Our fixation on pathogens has long overshadowed the potential of these benevolent organisms.”

In a new paper, Robinson argues that the millions of particles in the air – known as the “aerobiome” – are thought to have important health benefits and deserve as much attention as the particles that harm us: in this case, air pollution.

Each day we inhale and ingest microscopic life: up to 60,000 fungal spores, six-million bacteria, and the same for viruses.

“Each of us also emits a million biological particles, including microbes, each day,” says Robinson. “This constant interaction between our bodies and the environment is why the quality of our environment, including the air, is a key determinant of our health.”

Soil health is likely to be a vital factor in keeping the aerobiome diverse and in a health-promoting state, as the aerobiome largely originates from the soil, he explains. By enhancing and restoring nature in urban areas we can also “rewild” the air we breathe.

In a separate paper, Robinson and colleagues argue for the return of nature-play for children to optimise their health and immune systems.

Exposure to a range of microbes from the time we are born helps to train our adaptive immune system, so it can produce tiny armies of memory cells and protect us from harm in the future, he says.

“Certain environmental microbes called ‘old friends’, which have co-evolved with us over thousands of years, are thought to play important roles in regulating our innate immune system,” he adds. “Without proper regulation, our innate immune system will attack everything – including innocuous substances like pollen and dust, and even our own cells, which manifests as an autoimmune disorder.”

Being in nature, breathing fresh air and playing dirty are ways to get the exposure we need. But so is having a pet – particularly a dog – and having siblings, as another new study has highlighted.

Around one in every 10 Australian babies develops food allergies, which is the highest rate in the world. Previous studies have shown that having siblings is protective against the development of allergies.

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A new study, published in The Journal of Allergy and Clinical Immunology, found that the reason babies with older siblings have a decreased risk of allergy is because they have a much more mature gut microbiome by the time they turn one. In short, they are exposed to a more diverse range of bugs.

Professor Tang, who was a co-author on the study, explains that our lifetime risk for chronic illness is set in the first three years of our lives. “If you build a robust system at the beginning, you’re more resistant to insults throughout your life,” she says.

Children who have reduced exposure to microbes during this time because they don’t have siblings or pets, were born by C-section, have had multiple rounds of antibiotics or are not breast-fed are at a higher risk of developing allergies, asthma and chronic conditions.

Those living in a highly sanitised environment or who do not have enough access to nature, as was the case for many young children during COVID, can also suffer.

Some experts have suggested that we may see a generation of kids, born during COVID, suffering allergies and other illnesses because of their lack of exposure to microbes. “Theoretically, it is a concern,” says Tang. “Young children in that first three years would have had less exposure and that leads to suboptimal immune programming.”

Trying to improve our microbiome later in life makes “much less” of a difference, Tang says.

Still, what’s important for kids is also important for adults: being in nature is vital for body and mind; a diet rich in fibre, with plenty of fruits and vegetables, is an important source of nourishment for the good bugs in our guts; and though it’s not fully fleshed out, UV and vitamin D may also modulate our microbiome. As for whether supplements like probiotics make a meaningful and lasting change, Tang says it’s unclear.

While basic hygiene, like washing our hands, remains as important as ever, it’s vital to let children get a little dirty. Even if it requires some extra loads of laundry, their health depends on it.

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