Play dirty

I grew up building ‘dams’ in a local stream, exploring the ‘wilderness’ of Cape Town’s southern suburbs, climbing trees, ‘helping’ out in the garden, wrestling with my pet dog, making mudpies (yes, that was a thing) and generally getting down and dirty.

Now this wasn’t a conscious strategy on the part of either me or my parents, it’s just what kids did back in the mid-20^th century. But recent studies have suggested that it really is the best way to bring up your children. And the marketers of laundry detergent would agree.

Really, you’re suggesting our kids play in the dirt?

Okay, we’re not actually suggesting you let your newborn crawl through the kitty litter box, and we are aware that – in many urban spaces – the ground (or dirt, or soil) can be quite polluted. But researchers studying the huge increase of allergies and auto-immune conditions over the last few decades have come up with a scenario called the hygiene hypothesis. In short, the hygiene hypothesis states that children born by C-section, who are kept in a super-clean environment that is regularly sanitised, are regularly exposed to antibiotics, and are rarely exposed to animals, soil or plants, never get the chance to fully develop their immune systems.

Let’s just deal with some terminology here – we’re not talking about ‘strong’ vs ‘weak’ immune systems – we’re talking about immune systems that react appropriately. Someone with allergies or an auto-immune disease actually has quite a strong immune system – but one that struggles to differentiate between friend and foe. So, for example, it will react to daisy pollen in the same way it would react to SARS-CoV-2. Now, clearly, that’s not appropriate. No-one ever died from daisy pollen. Unless they were buried in it. Or their immune system overreacted to a ridiculous degree. So it looks as if we are bringing up a generation of humans with maladapted immunity.

But that’s all just speculation, and propaganda spread around by New Age hippies. Right?

Wrong.

The Finnish ‘dirty daycare’ experiment

A recent study in Finland measured and compared gut and skin microbiota in 75 urban children aged between three and five attending 10 daycare centres in two Finnish cities. Three nature-oriented daycare centres (with 23 children) served as a positive control, as they already had green playgrounds with lots of different plants. Three standard urban daycare centres (with 16 subjects) with playgrounds of approximately 500 square metres but almost no green space or plants served as controls. Four ‘intervention’ daycare centres (with 36 children) had their playgrounds planted with 100 cubic metres of forest floor, and 200 square metres of sod. The children were encouraged to play on the ground, and to garden in the supplied containers.

The results showed that the children in the intervention group had a marked increase in gut and skin biota, which – one may hypothesise – would lead to healthier immune systems. The researchers claim that this is the ‘first human intervention trial in which urban environmental biodiversity was manipulated to examine its effects on commensal microbiomes and the immune system in young children’.

It’s not about the dirt

But the study has a number of shortcomings. While the results show that children exposed to a range of plants – and the microbes on the plants and in the soil – appear to develop more diverse gut and skin microbiota, it does not explain how or why. A 2017 University of British Colombia study claimed that it was not so much the act of ‘playing in the dirt’ that enabled children to develop healthy immune systems, it was the quality of that dirt – and more specifically the biodiversity of the soil itself and the plants it supported:

‘Importantly, if early-life exposure to environmental microbes increases gut microbiota diversity by influencing patterns of gut microbial assembly, then soil biodiversity loss due to land-use changes such as urbanization could be a public health threat. […]

‘Growing up in microbe-rich environments, like traditional farms, results in healthier children. Therefore, the prevalence of inflammatory disorders may be higher in modern cities because of reduced exposure to beneficial microbes from the environment, such as microbes from house dust or zoonotic microbes from animals. Indeed, exposure to household pets has been shown to alter the infant gut microbiota and reduce allergic disease.’

So what does that mean for residential estates?

This is just one more of many good reasons to ensure a healthy biodiversity in the public spaces in your estate. Yes, we all like neat expanses of lawn and manicured flower beds, but – if you have the room – it’s great to have space that’s a little wild, a little free. Create spaces where kids can ‘play in the dirt’. It’s good for them physically and mentally.

And it’s good for your bottom line. As more studies show the connections between immunity, overall health, early childhood development, biodiversity and time spent outdoors, families will be willing to pay a premium to live in a place where their kids – and their pets – can ‘play dirty’ safely.