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Dirt: A Paleo Superfood?


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Over the past few decades, chronic inflammatory disorders such as inflammatory bowel disease (IBD), allergies, and asthma have become significantly more common in industrialized countries.

There has been an increase in the incidence of IBD, particularly in children, with 20% to 30% of patients having an onset of symptoms before the age of eighteen (1) Rates for food allergies have been steadily rising, and seasonal allergies have more than doubled since the 1970s. (23) There has also been a sharp rise in asthma rates for both children and adults in the past decade, with nearly one in ten children and one in twelve adults suffering from the disease. (4)

Even autoimmune conditions such as type 1 diabetes and multiple sclerosis have increased at rates too rapid to be accounted for by changes in our genetics. (5) Many healthcare professionals, research scientists, and epidemiologists are at a loss for why the rates of these inflammatory diseases are increasing on such a steep incline.

Could it be that we’re all just not eating enough dirt?

Our culture’s obsessive attention to cleanliness, sanitation, and hygiene may actually be having unintended consequences on our immune system.

While a sanitary environment may be crucial in areas such as hospitals or food production, our general avoidance of dirt, bacteria, and other infectious agents may be causing our under-stimulated immune system to become overreactive to benign antigens.

The “hygiene hypothesis” or “old friends hypothesis” suggests that the increased prevalence of inflammatory disorders is the result of defective immune system regulation due to reduced exposure to an adequate variety of microorganisms. (6) Since our immune system evolved alongside a massive variety of different microbiota, both commensal and pathogenic, the recent changes in society and environmental exposures to germs may play an important role in the global increase of inflammatory diseases, particularly in urban settings. (7)

Evidence for the hygiene hypothesis of inflammatory disease has recently been demonstrated in controlled animal trials.

In a 2012 study, researchers examined the immune system of “germ-free” mice who had been bred to lack gut bacteria, and compared them to mice with normal exposure to microbes. (8) They found that the germ-free mice had significantly more inflammation in the lungs and colon, similar to that found in humans with asthma and colitis, due to hyperactivity of specific T cells that have been linked to these conditions in both mice and humans.

What is most interesting about these results is that if the germ-free mice were exposed to microbes during the first few weeks of life, they eventually developed a normalized immune system and avoided inflammatory disease.

On the other hand, those germ-free mice exposed later as adults never recovered a fully functioning immune system. This demonstrates a crucial time period during early life where the immune system must be properly conditioned in order to function normally. Of course, this effect needs to be demonstrated in humans, but these preliminary results are promising for the study of inflammatory disease development.

So what does this mean for us humans? Should we all start chowing down on bacteria-filled dirt?

Not so fast.  Don’t forget that not all organisms in the environment are “old friends”.  Some of them can cause significant disease, and even death.  However, the hygiene hypothesis does highlight the importance of the gut microbiota in regulating our immune system and overall health. Additionally, it further emphasizes the potential consequences of things that adversely impact our gut microbiota, starting with a cesarean section birth and formula feeding (instead of breastfeeding) and continuing later in life with overuse or misuse of antibiotics. While there are likely many different factors that play into the development of inflammatory and autoimmune conditions, the evidence of the hygiene hypothesis is robust enough that it should not be ignored.

One important take-home message of this research is the notion that certain crucial biological developments happen during the early years of infancy and childhood, and these developmental milestones cannot simply be recreated during later years of life.

This means that children are especially vulnerable to environmental inputs, both positive and negative, that may significantly affect their health later in life.

It also means – as I’ve pointed out several times before – that there’s more to health than food.  A nutrient-dense, whole-foods diet is certainly one of the best steps we can take to prevent disease and improve our health.  But it’s not a panacea, especially in the face of environmental and epigenetic alterations of the commensal gut microbiota.

While we cannot control every factor of our children’s future health and wellbeing, we can at least feel better about letting our kids splash in the mud, put toys in their mouth, or play with the neighbor’s dog. Beyond being a little less worried about protecting our children from germs, perhaps we should actually encourage them to get a little dirty now and then!

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      • Any experiments yet? I will try to culture them on FOS and potato starch soon at room temp in water.

        • It appears to work well. I split one capsule in 6oz water, then split 2oz of that to 12oz of water with either FOS, potato starch, or maple syrup. Growth: maple syrup > FOS > PS. There are a few caveats. The PS settled to the bottom and was probably inaccessible to most of the bacteria, whereas the FOS and especially the maple syrup mostly dissolved in the water making easy access to nutrients. Also, the FOS and maple syrup could potentially be selecting for less-than-desirable strains of bacteria. Either way, I’ll drink em all and see what happens!

          • Brock, how did you do with your cultured Prescript-Assist? How do you know that the culture was successful? What are the signs? Does the mixture get sour?

            • It works really well actually. Ive tried a few different fibers, but I like klaire labs biotagen the best (has a mix of a bunch of inulin/fos/arabinogalactan) but any fiber seems to work. RS is just slower because its difficult to mix. I open up two pills into a 16 oz water bottle from costco and split that into two water bottles containing the fiber of your choice. Typically ill double the rec dose (usually 10g) of fiber and then shake it up. After about 3 days it gets kind of fizzy, but not so much that the bottle would explode like say from brewing kefir. It also starts smelling like feet. I keep it in my sock drawer so i remember to shake it up at least once a day. I drank about 8oz of this mix after a week and had a headache within an hour or two from supposed die off, I dont get this with just one capsule of prescript assist so i assume the dosage is massively increased from my “cultured” version.

              • Brock, I am afraid that the reaction you get to your culture is due to the yeast being grown in your culture (confirmed by the “smell like feet.”) Somebody has been culturing probiotics using vegetables in a container fitted with an air lock. The air lock prevents air from getting into the mixture, so yeast and unwanted bacteria doesn’t grow in the culture. I understand you can buy the “Picklemeister” air lock lid for $10. The lid fits any size mason jar you can buy in a grocery store. (see the following website http://curezone.com/forums/fm.asp?i=1205862 ). If you decide to use the air lock to grow “Prescript-Assist,” please let us know you it goes. Please note that “LB17” is NOT a soil-based probiotic.

                • That would be terrible! I do not think that is the case though. The lids were sealed completely, its just a normal plastic water bottle, and airtight. I may have gone overboard on the feet smell, especially since re-reading my comment that I had them in my sock drawer > <
                  I culture cancer cells for a living so I know a lot about contamination.

                  I have yet to passage or re-innoculate other fiber/jars, i've only broken open a new pill and put it in with fresh 'food' for them and let it go for a few days. The headaches went away after the first week or so of trying this and I'm feeling better than ever lately, but ymmv.

                  Overall this is a neat trick to get the most out of an expensive bottle of pills, but it is highly dependent on the fiber/food used, culture times, and persons own gut flora. Best bet is to experiment and see how it goes.

  1. I’ll admit, during flu and cold season I’m a little obsessive about the sanitizer with my first grader and I know her teacher is too. However, I am not uptight about her playing out in the yard and then grabbing a handful of chips. I grew up watching the men in my family wolf down sandwiches while working in the garage or in the yard and lord knows I did the sane as a kid. And guess what? We’re still here!

  2. It pays to live in a country like India. We have no choice but to be exposed to germs. But inflammation is also caused by stress and diet. And that is not so great with us being the diabetes capital of the world. There is evidence that diabetes and heart disease are also caused by inflammation.

  3. has always been my philosophy and how i did raise my kids. thanks for writing this!

  4. I live on a small farm and am and asthmatic, I have horses, sheep cows, rabbits and chickens as well as dogs and cats, we live and eat and grow our own food sustainably. and without as many chemicals as humanly possible. we are not certified organic, but we grow with organic methods, I have had 3 children who tho my 3rd has reactive airways when he becomes ill, none of my kids suffer asthma symptoms like I had from age 3. since the farm life my attacks are MUCH less , but I still have issues if I get a respiratory cold, or virus. but as a kid I was told anything that grew hair would hospitalize me, ESPECIALLY horses. I have 11 and have had horses since childhood. my parents allowed me to self vaccinate for my asthma rather than those allergy shots. I went near the animals in moderation and bathed as soonas I left them , until I developed a tollerance. I completely believe in co existing with our environment makes stronger immune systems.

  5. While I think there’s some truth in the hygiene hypothesis, encouraging people to actually eat dirt seems a little worrying. While I would happily eat unwashed raspberries straight from the bush (I did a lot of this as a child), I definitely wouldn’t gather dirt at ground level in our modern overcrowded society. There are lots of harmful bacteria and pathogens down there especially where dirt is contaminated by faeces.

  6. Well done Chris.
    I was diagnosed with Lyme disease today, so I can attest to the fact that modern antibiotics have their uses. However, I agree with you that we do need to be more judicial with antibiotic use.

    As far as eating dirt, I doubt it’s necessary or even healthy. As far as playing in the dirt, well who doesn’t love that? I would bet there are some unique psychological benefits as well, especially for kids.

    – Armi

  7. Please put me down for ‘not buying the dirt hypothesis’. I am, have been, and always will be about as woodsy and dirty as a modern American can be, and I also suffer from nasty Crohn’s disease. My kids will no doubt be barefoot and dirty too, and I hope it helps strengthen their immune system against common, infection-based problems, but in my n=1 (and in this particular topic an n=1 seems somewhat acceptable) it hasn’t helped at all with the autoimmune issues which you speak of. I’m sticking with diet, sleep and stress in that department!

    • Autoimmune disease is multi-factorial. The fact that you were exposed to dirt but still developed an autoimmune disease does not in any way disprove the hygiene hypothesis. It simply suggests that another factor known to contribute to autoimmune disease, such as a pathogen or gut permeability, was present in your case.

      • You said: “What do you all think about the hygiene hypothesis? Do you let your children play in the dirt? Tell me your thoughts!”

        I wasn’t on a quest to disprove the hygiene hypothesis. My thoughts, and reason for writing a comment, were that this seems really, really minor compared to diet (including intestinal permeability), sleep and stress. I write this as someone that thought for a long time thought they were doing all they could by avoiding anti-microbial soap, SLS type chemicals, deodorant, etc. I still don’t use any of those things, but that attitude contributed to my being blind to the real culprits for my AI problems.

        However, I can definitely see based on your response where I may be missing the point: most of what I’m reading these days focuses on gut permeability as the real cause for autoimmunity, not pathogens. I guess if aquired pathogens (and I’m thinking bacteria, virus here, not gluten etc) could cause AI problems, the hygiene hypothesis becomes more important? I would love to hear more about the role of pathogens in causing autoimmunity.

    • Also, do you think it’s safe to take the therapeutic dose for a few months if your situation is bad enough? Did you start at the 2 caps right away or build up to it?

  8. Through what I found, the best “safe dirt plan” is the following:

    At birth a baby must be given a 10ml shot of Mutaflor (the friendly Escherichia coli Nissle 1917). This bacteria prepares the intestins for the arrival and successful settlement of other lactic-acid bacterias (lactobacilli and bifidos) and has a lot of benefits on it’s own. Dr Natasha Campbell-McBride talks about it in her book on GAPS.
    some links:

    then, a few days later, a good mix of bifidobacterias with or wthout lactobacilli (documented strains, Jarrow has good ones) could be given:

    and finally, when the baby is weaned and starts eating normal food (animal proteins, good fat and vegetables), then it should be given soil based organisms because they are the only ones capable of digesting undigested non-dairy food thus preventing rotting in the colon and producing a healthy gut (they are fungus worst ennemy!) while producing vitamins and a lot of other useful substances. that’s exacly what they do in the soil. all animals (incliding our ancestors) eat a lot of these. The best and safest way to do this is by taking prescript-assist (until something better is out!). It’s double blind tested for safety and efficiency.

    • hey,
      i’m following a similar program (but i’m 28!). i’m currently taking mutaflor, some lactobacilli and s.boullardi. i’ll be swicthing to mutaflor and prescript-assist for a while soon though, then back to mutaflor and some lacto/bifido’s. and doing a mostly GAPS diet. how long do you recommend taking the prescript-assist for? i knwo the regular time is a month but is that long enough to make a difference in gut dysbiosis, since it doesn’t colonize the gut?

      • Hi Denise,
        I take prescript assist for ever as it mimicks the healthy dirt to which we’re supposed to be exposed. I see no point (but it’s me!) to take any lactobacillus and bifidos as they never did anything for me that I can feel (contrary to PA as explained above). Mutaflor is great for those who have ulcerative colitis but otherwise I don’t know much about it. I know that if a new born gets it, he or she will keep it the whole life (unless distroyed but antibiotics!). Now that I’ve been taking PA, s.boullardi isn’t helping anymore, soil bacterias in PA should be killing them at sight! moreover, it’s not good to take s.boullardi for more than a month as it would give allergies (it’s a yeast, don’t forget).
        I try to eat a lot of colorful vegetables, fermented cabbage and rawmilk cheese (vive la France!) and this keeps my gut healthy.
        hope it helped

        • Hi Milad, if yeast causes allergies wouldn’t kefir etc cause allergies too? I read that it’s best to take prescript-assist for one month twice a year for maintenance, and include probiotic foods the rest of the time. Does it work for candida/SIBO? I’m pretty sensitive to ferments at the moment though. Do you take the two daily capsules together or one in the morning & one at night? I know mutaflor will take hold more quickly in children but can take a while in adults, esp those with messed up gut flora.

          • Denise, I took prescript assist for 1 month, 1 capsule in the morning and one at night. after that you only need 1-2 capsules per week for maintenance. You can also take it as you said. For more questions, you should ask Chris as I don’t use Kefir. Read all my previous posts on this page to get all the info you need on PA.

            • Hey Milad,
              Thanks! The fermented veg/dairy is a good plan. Did you have SIBO or candida or gastritis problems before taking prescript assist?

  9. We love dirt! My boys are regular Huck Finn and Tom Sawyer!! LOL! I let them eat things they found on the floor while crawling around when they were babies, I let them run barefoot outside (like I could stop them if I wanted to!!), I only require handwashing if the hands are black before eating! We garden and grow veg in our smallish garden in all the flower beds, they cuddle their bunnies and roll on the grass. They are rarely sick and much happier when they are dirty! I’ve actively banned anti bac products from the house!!! I have one natural antibacteria spray for when we have a nasty sickness in the house (rarely used) and I do use hand sanitizer in my bag when we are out and about and there is no hand wash facilities (we travel alot). And yes……we pick things up that we drop on the floor and put them back on the plate to eat – 10 second rule! 🙂

  10. I saw in a comment above that you’ve done Helminth therapy? Have you written about that anywhere? I would be fascinated to hear about your experience. As much as we focus on microbiota, I am keenly interested in the roll of parasites in appropriately “tuning” our immune system.

    I agree there are places for appropriate microbial control, and the hospital certainly is one such place, but I personally HATE the brigade of antiseptic hand lotions outside every room (what’s wrong with soap and water, and that aloe/alcohol “moisturizer” is just gross). If we believe (as I do) that one of the rolls of a normal healthy microbiota is actively out-competing pathogenic microbiota in our gut, why is this not the case with our skin? Surely having healthy commensal bacteria on our skin is better than having nothing when exposed to pathogenic skin bacteria. Interesting to think about at least…

    It all makes me feel very fortunate that I was raised outdoors in woods, streams, and gardens getting very dirty… Of course, it’s important not to think that all dirt is good. When I worked in a parasitology lab I isolated Baylisascaris procyonis eggs from some samples we’d collected at a park. Accidentally ingest those and you might be dead…

  11. Great article as usual. I personnaly have always suffered from allergies and digestion and skin problems. until 5-6 years ago I had 1 or 2 courses of antibiotics each year for colds. I was not a happy person at that time and knew nothing about vitamin D and effects of stress on immune system. in 2008 I learned about paleo and started taking care of myself while changing my life to become a happier person. I tried all the well known probiotics(Dr Ohira, jarrow…) but none really helped my digestive problems. I still couldn’t digest well fruits and vegetables, they just passed through.
    Then, I read this post on Dr Dean’s site: http://drcarolyndean.com/2011/06/take-soil-based-probiotics-and-eat-dirt/ it was a great EUREKA for me. It seems that soil based organisms are the only ones that all animals eat on a daily basis to help them digest food and fight disease(fungus…). Lactic acid bacterias are only good when the only food is milk(infancy). I take my time to do my own research on each strain and finally gave it a shot and boy, I don’t regret it! it was life changing! my skin was cleared and my body odor vanished (you know, at the end of the day). and no more gaz! this blew me away! Besides, I could find no trace of undigested fruits and vegetables in the stools, AMAZING! I just noticed that these little bugs don’t like rice (in big amount) very much but sweet potatoes are well digested. I took two capsules a day for a month then just 2 per week for maintenance. here are all the studies done on it (IBD, flatulence, etc): http://scholar.google.fr/scholar?q=prescript+assist&hl=fr&btnG=Rechercher&lr
    the company is here: http://www.safermedicalinc.com/

    • I’m half way through a bottle of prescript-assist right now. I was hoping for some sign like a bolt of lightning from the heavens, a gnarly die-off reaction or maybe miracle of all miracles a firm stool that sinks like a log, but alas it seems like I might as well be eating saw dust. I’ve definitely considered eating dirt and I don’t over-wash my veggies, but I might have to go out on a limb here and try the real deal in larger quantity just to see what happens. I wonder if farm dirt is the way to go for the average person. Farm dirt is probably bio-logically very active, but the things people typically feed plants would seem to have somewhat more potential for harboring undesirable zoonotic infection than dirt from a more natural setting. I eat a fair amount of garden dirt at home just because I purposefully don’t over-wash stuff, but I don’t import manures and such for my garden either. One last note, I read somewhere that it is beneficial to give pigs in confinement dirt to eat especially when they get sick, and also just to keep them healthy.

        • Hi Alicia and Steven,

          For Prescript assist to be effiicient needs to be taken with consistancy 2/day for a month then 1 or two parweek for maintenance. after a few months I can say that it had a very deep impact on me and I’m very satisfied. the first two weeks I could litterarly feel them in the gut a kind of tickling but I felt really good. But the strange yhing is that some of my friends felt absolutely nothing but one of them noticed a much better immunity. two other people had some had some headaches (maybe candida

  12. Speaking of gut flora, I’m still trying to understand the FODMAP connection. It seems as though you are recommending FOS (http://chriskresser.com/myths-and-truths-about-fiber) for increased beneficial bacteria, yet there is good evidence to follow a diet low in these components: (http://www.archevore.com/panu-weblog/2011/2/5/fodmaps.html). So are they health-promoting, or harmful? Or is this more of lactose intolerance type issue, where dairy can be a very beneficial thing, as long as your gut has lactase.

  13. Oh man, I have been thinking this for 10 YEARS! I like eating my carrots right out of the garden, a good swipe on my apron and chomp chomp. Seems reasonable.

    Chris, perhaps you could write a post about soil based probiotics pros/cons, suggestions, concerns, etc?


  14. Our children play in the dirt, mud, sand, water, vegie garden, you name it. They share their living space with animals, are unvaccinated, and are the healthiest kids I know. Children have a need to connect with the Earth, which is why they thrive when given that opportunity. And good luck convincing them they need to wear shoes outside!

  15. I would not be surprised if it was a factor, but there are many factors including all the unhealthy mothers, formula diets and crappy baby food in general, lack of sun, lack of exercise, chemicals everywhere, etc.. My sister in law is terrified the sun will touch her baby even for 5 minutes! She ‘knows’ its bad and will lead to cancer because ‘all the experts say so.’ And have you ever seen what is in baby food these days? Some of it tastes horrible and the rest tastes like super sugar bombs because it’s made with fruit concentrate or grape juice concentrate, all stored for long periods and processed to death. Then even the youngest children are expected to sit totally still and quiet in chairs in classrooms for hours, which is not natural to the species. No surprise most people are physically ill and stressed out. It’s starts before birth and dirt is only just one factor of many. Children on farms not only get in the dirt more, but they tend to eat more real food and get more sun and exercise, both parents and children, so it’s tricky to tease one factor from the others.

  16. 25 years ago sitting in my nutrition class at UCSD, I remember Dr. Paul Saltman (RIP) saying “Let your kids lick the floors, if you want them to be healthy. There are lots of metal cofactors for your enzymes on dirty floors.” Smart man…and a great teacher.