Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
7 Feb

The Dirt on Dirt

The prevailing opinion at MDA is that listening to one’s body is good policy. Natural instinct has been kind to us over the years – just as long as we listen to it. Oh, sure, some instinctual behaviors have little relevance nowadays and should be ignored (like our tendency to tribalize and shun newcomers for protection – made sense when we were living off the land in small inclusive clans competing for resources, but today it just causes war, racism, and nationalism), but most instincts are hard-wired into us for a reason. Consider salivation, which tells us delicious, wholesome food is to be had (I know I’m not the only one with an utterly Primal tendency to drool at the prospect of a rare steak), or our sense of fairness, which makes for a more harmonious environment (good for survival and for everyone involved). We like to stress the importance of listening to your body’s natural inclinations.

By definition, pretty much any instinctual behavior confers evolutionary advantages (otherwise it wouldn’t have been kept around for so long) – this is the basis of the Primal Blueprint, with our focus on living in accordance with our Primal ancestors (whose actions, behaviors, and diets were highly instinct-driven).

A series of recent studies examined a young child’s tendency to eat dirt, lick stuff on the ground, and put whatever he can find in his mouth. Is there some evolutionary benefit to be conferred from eating dirt? We have a rather unhealthy (or is it?) obsession with dirt, so we were interested to read the results.

Dirt vindicated, once again! Mud pies, it seems, aren’t just a tasty way for a fledgling baker to get his start in life. The ingestion of dirt introduces a number of bacteria and viruses that actually spur the development of our immune systems. And certain worms have been shown to redirect messed up immune systems that would normally result in autoimmune disorders, asthma, and allergies.

When he puts random things in his mouth, a child is letting his “immune system… explore his environment,” writes immunologist Mary Ruebush. That kid with a dirty mouth isn’t increasing his chances of getting sick; he’s actually giving his immune system “practice” figuring out what’s benign and what’s dangerous.

As we’ve discussed before, over-sterilization of our environments can actually be counterproductive. Scientists suspect that even as the increasing sanitization of developed countries has eliminated some health concerns – contaminated food and drinking water, for example – it has also introduced a whole host of other issues, including rising levels of multiple sclerosis, Type 1 diabetes, inflammatory bowel disease, asthma, and allergies – all potentially stemming from a reduced, or eliminated, exposure to bacteria early on. We’ve gotten “cleaner,” but in doing so we’ve eliminated both good and bad dirt. We’ve also strengthened the bad stuff. All those antibacterial products – Purell and the ubiquitous variants you see in purses, attached to kids’ wrists, in “fun size” – might actually be creating antibiotic-resistant strains of dangerous bacteria. Remember, evolution works both ways (and much more rapidly in bacteria).

That’s not to say we shouldn’t wash up. We should, especially if we’ve been touching dirty diapers, handling raw meat, or using the toilet. Just don’t go overboard with it. Basic soap and water are good enough.

And of course, it goes without saying that kids should have access to plenty of dirt growing up – if not for their immune systems, then for the fact that playing in the dirt is an awesome part of childhood that no kid should be without. It’s in line with the Primal spirit of play, too.

Oh, and you might want to ease up on the strict “wash your hands before dinner” rules – we might be doing more harm than good.

beccaplusmolly Flickr Photo (CC)

Further Reading:

Should I Get a Flu Shot?

8 Ways to Reduce Your Chemical Load

The Dope on Energy Drinks

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I love the caption under the picture! I think I’m going to use that in my scrapbooking, I have the perfect picture for it.

    new_me wrote on February 7th, 2009
  2. I couldn’t agree more about society going overboard on “cleanliness”, and thus, making our immune systems weaker!

    Hell, I survived 3 years in a fraternity house with 35+ dudes. If people can do that, then they can live through just about anything :)

    Ryan Denner wrote on February 7th, 2009
  3. Haha good point Ryan. I shared my University house with 11 other guys and I think some new organisms started growing in our kitchen it got that bad.

    Tom Parker - Free Fitness Tips wrote on February 7th, 2009
  4. Problem is that the dirt that is present in most urbanized areas isn’t the kind of dirt we used to ingest. The chemical and bacteriological load is likely to be quite different – and not different in our favor, sadly.

    fasching wrote on February 8th, 2009
  5. Overprescription of anti-biotics, not ethanol-based hand sanitizers, are causing the evolution of superbugs. Just sayin.

    Todd wrote on February 9th, 2009
  6. what in the hell is dirt lick?

    aisha wrote on April 15th, 2009
  7. Dear Mark,

    As a person making his PhD on children’s soil eating and object mouthing behaviour, I must say ingesting little amounts of even natural, uncontaminated soil may be HIGHLY dangerous, because the natural levels of metals in soil can have toxic effects. This is especially valid for children ingesting soil.

    We are already exposed to heavy metals via food, air and water (called background exposure) and no matter how clean we eat, drink or live, we cannot prevent it. Additional exposure to heavy metals through soil ingestion, environmental pollution or any other reason adds to the present risk levels.

    For example we are exposed to high levels of arsenic through water and food, and this metal is carcinogenic in very low concentrations. Soil always has a certain level of arsenic. Any amount of soil ingested even in levels of miligrams adds to risk.

    Children’s soil eating behaviour has many origins, but mainly they do it not because it is very useful and heathy for them but due to their curious nature or presence of mineral deficiency. Eating soil because of being curious or needing minerals is like eating junk food when you are curious about the taste or you are very hungry and in need of nutrients. As we know, eating that junk may satisfy our curiosity or hunger, even give us pleasure for a moment, but it is not healthy.

    Although I accept and admire many of your views, I should say one should never ever advocate ingestion of soil/dirt/dust, and should stay away from deliberate or accidental ingestion of these material because of the availability of metals due to the natural concentrations in main rock and soil. I don’t even consider environmental pollution or other stuff. And i repeat, this may be a very serious issue, especially for children.

    I think the message of this article needs a little polish up.

    Regards, Mert.

    Mert wrote on March 4th, 2010
  8. Leave it to someone getting his PhD to ruin eating dirt. Darn you Smart PEOPLE!!!

    Matt Forrester wrote on March 18th, 2010
    • What do you mean? Have you read my post with an intention to learn something new, or what? I’m trying to contribute.

      I’d rather prefer to hear what do you think about the arguments stated, and I’d better like to know yours, as well as other people’s.

      Mert wrote on March 18th, 2010
      • I think he meant: you make a really good point… damn you for ruining what could have been playful and fun (it’s all. your. fault.)

        Can you link a few sources on the nutrient/contaminant/bacterial profile of dirt for us? Where is the Arsenic coming from, apple juice spills on playgrounds (sort of kidding… stupid juicy-juice)?

        Adam Long wrote on March 21st, 2012
  9. Absolutely, there are contaminated in dirt. Granite rocks are responsible for leaching uranium for example (if I am remembering correctly, I’m in chemically induced menopause for breast cancer). There are also a lot of contaminates in the air, in our household chemicals, our vinyl shower curtains, in food from California organically grown but dusted from fallout from rocket testing, etc.. Consider the source of your dirt. We have a garden and a greenhouse and have built up our own soil, it’s about as safe as we can make it and I my kids eat a dirty carrot or two, so much the better!

    Kes wrote on April 30th, 2012
  10. I’m more concerned with washing my hands after handling tons of stuff at a store (because of dirty people) than I am with dirt or raw meat. I don’t even think I wash my hands – just rinse of debris – after handling meat or touching stuff outside.

    Lauren wrote on September 27th, 2013

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