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How to Safely Expose Your Kids to Dirt

If you’ve been reading this blog for any reasonable stretch of time, you know that I’m a big proponent of getting dirty [1]. By overvaluing sterility and fearing dirt – in our homes, our guts, even our hospitals [2] – we’ve impaired our immune systems, our gut and digestive health, and even our mental health. The world is a dirty place, and we need to accept that. We need to embrace it, within reason, especially if we’re wards of tiny still-developing humans for whom exposure to dirt has important and resounding benefits. You’ve got the benefits to current and future immune function that I’ve gone over in the past [3]. Then you’ve got soil-based microbes like Mycobacterium vaccae, which increase serotonin levels [4] and may be responsible for the positive disposition that seems to be universal among hobby gardeners. It’s probably why kids have a natural inclination to engage with the ground, get handsy with the soil and make out with mother nature. I say we let them.

But we have to do it right. There’s good dirt and there’s bad dirt. And sometimes the good dirt can be contaminated with bad stuff. We must then promote reasonably safe exposure to dirt. How so?

Let them play in the dirt. Don’t lose your mind if they eat a teaspoon or two (you don’t have to provide actual teaspoons). Encourage mud puddles, or “muddles,” to facilitate greater surface coverage. Actually, encouragement is unnecessary, as kids naturally gravitate toward mud and dirt.

Avoid triclosan handsoaps. Triclosan is an anti-bacterial agent, an antibiotic. It kills some bacteria but promotes antibiotic resistance in those who survive [5]. And don’t forget that we have commensal/beneficial bacteria on our skin [6] that help keep out the pathogens. If triclosan clears a path through those guys, the pathogens can gain a foothold. Plain soap and water are all you need.

Avoid excessive handwashing. If you live in a place like Karachi, Pakistan, where open sewers run through slums [7]fastidious handwashing can improve child well-being and overall health [8]. I’m not so sure the obsession with handwashing in the relatively pristine environments of more industrialized nations is warranted, and I suspect it’s counterproductive. A little dirt under the fingernails rarely hurt anyone.

Test your soil for contaminants. Soil can harbor heavy metals like lead, arsenic, and Viking death metal (sorry, terrible subgenre joke that my employees insisted I include). I wish I could make broad pronouncements about soil in general, but I cannot; heavy metal content varies widely from country to country, state to state, town to town, and even backyard to backyard. Older houses may be more likely to have lead due to deteriorating lead paint. Do a search for “soil heavy metals [your town]” to find information about your specific area. Another option is to actually test your soil for heavy metal contamination; this is a good guide for taking soil samples [9].

Pick up dog, cat, and wild animal poop regularly. “Poop is everywhere” is one of those factoids that people love telling to other people. But microscopic amounts of fecal matter are one thing. Full-on turds are another. Also, wild animals like raccoons (who whether you see them or not are probably near you) almost uniformly carry a deadly parasite that can trigger dangerous inflammation [10] in children. In case you haven’t gotten on board yet, feeding a raw prey-model Primal pet diet to your cats [11] and/or dogs [12] has the benefit of making the poop easier to clean up.

Weed using non-toxic approaches, like your hands, boiling water, or vinegar. In previous posts, I’ve discussed the downsides of weed control using Roundup [13], the glyphosate-based herbicide that inhibits the shikimate pathway in both plants and bacteria (but not mammals). Since we mammals rely on bacteria in our guts to maintain and promote good health, however, Roundup hits us indirectly. The whole idea of dirt exposure in kids is to “seed” them with beneficial bacteria, so spiking their dirt with a bunch of bacteria-killing Roundup [14] with a half-life in soil of nearly 100 days (PDF [15]) is counterproductive. A little elbow grease, a big pot of boiling water (maybe two big pots; watch for errant kids), and/or some white vinegar directly applied to the weeds will take care of them without putting your kids in harm’s way.

Favor “pesticide-free” parks. Public parks are a great place for kids to play, run around, get dirty, meet each other, and generally act like kids. But if they’re going to be playing with, in, and around the dirt – and they will be – focus on parks whose grounds aren’t doused daily in pesticides. Eugene, Oregon has a “pesticide-free parks” program [16], and I imagine other places do, too. Look around for similar lists in your area. Barring that, contact your city officials and make a list yourself.

Sampling is normal, but gorging is suspicious. If a kid is chowing down on dirt, really savoring the soil, and displacing actual food, something’s up. You might need to take a closer look at his diet and look for egregious nutrient deficiencies. Some candidates:

Get a furry pet. Cats and dogs have different effects. While I like cats (even though they’d kill us all if they weighed as much as a yellow lab), dogs [29] seem to be more beneficial to overall immune development in children. In one study [30], cat exposure in early childhood had no effect on atopic dermatitis, but dog exposure was protective. In another [31], early dog exposure led to big improvements in general resistance to colds; cat exposure was also protective, but less so. However, a 2008 study [32] found that cat exposure was protective against asthma while dog exposure was not. What do we make of it? If I had to guess, I’d say having both a cat and a dog would be most protective against the broadest range of immune disorders.

Be careful about cat litter, especially if you allow your cats outdoors. Outdoor cats who hunt rats may carry the Toxoplasma gondii parasite [33], which your kid (or you) can pick up when handling cat litter. T gondii has been linked to depression and suicide [34]. (And if your kid happens to be a rat, the parasite will abolish all fear of cats, make cat pee irresistible [35], and probably lead to his or her gory death.) Even if your cat doesn’t have the parasite, cat litter isn’t going to impart many beneficial microbes and as such should be summarily avoided. You’re not missing out on anything by not sprinkling crumbled cat poop in your smoothie.

Go on lots of hikes, go camping, and play in creeks, streams, and rivers. The backyard is great (and is a great way to introduce tent camping, in fact). It’s handy, it’s right back there, and it’s safe. But it’s not enough. There’s an entire world of dirt that’s just begging to be traversed [36] on all fours. For optimal dirt exposure, take your kid out to the great outdoors [37]. Go on hikes [38]. Pause to look for anthills and interesting fungi. Tramp through creeks. Pause to look for crawdads and tadpoles. Visit deserts, redwood forests, swamps, rainforests. Wherever you are, you don’t even have to make sure your kids “get sufficient dirt.” They’ll find each other.

As you can see, most of the advice is common sense. It’s mostly “let your kid do what kids will” and “but be reasonable about it.” Soil smoothies and cat poop snacks, bad. Mud mustache and a little dirt under the fingernails, probably okay.

That’s all I’ve got today, folks. I hope it was helpful to all you parents out there. Even if you’re not a parent or kid, this stuff works on adults, too. So get to it!