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. (2, 3) 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?
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.
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.
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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Thanks Chris, and I agree. One needs an immune system that has been challenged by the environment one lives in. Sally Fallon says that it is tradition in China for mothers to not wash themselves when breast feeding, they understand the baby will then be exposed to the germs on their mother’s bodies and learn to adapt. I’ve heard Joel Salatin say every kid should eat a pound of dirt before they “know better”. I sure did, even growing up in Los Angeles I was ALWAYS playing in the dirt. Making mud pies was a favorite activity!
Pasteur was wrong or at best only partially correct with the “germ theory of disease”. Bernard, Bechamp, Cannon, and Page, Price, etc. were correct.
It would benefit all to read: “Rethinking Pasteur’s Germ Theory” by: Nancy Appleton
Yes, let kids go out and play on non-chemically treated dirt, grass, and wildland’s.
Finding land that has not been contaminated by heavy metals, pesticides, flame retardants, etc… is nearly impossible these days. My kids play barefoot in our yard, but we are the only “green” household on the street. Everyone else uses pesticides and fertilizers. I am not a clean freak, and chemicals are not allowed in our house, but I still worry about the toxins that we are bringing in.
LaLonde was right 🙂
How do GMO’s figure into this mix; I am of the opinion that they contribute to gut dysfunction.
One of my personal practices is not washing my CSA/farmers’ market veggies. If I know the farm, I figure their dirt is of good quality.
I have been saying this same thing for a long time now, we are “hand sanitizing” ourselves to death! I also believe this is why kids in other countries don’t have peanut allergies, etc. I have a leaky gut and celiac so I have had my share of issues with my digestive/immune health. I was also a c-section and on formula as a baby. Now I rarely wash my fruits and veggies (organic only) and allow myself to eat the small amount of dirt that is on them. I never tell anyone this or they would think I am crazy, but I think my health has only improved from doing it. Thanks for a great post!
I am fine with the old friends hypothesis but frankly an enemy of the hygiene hypothesis, at least in terms of how it is commonly portrayed in the media. Today’s kids are frequently in preschool, where they get plenty of dirt and certainly plenty of germ exposure. And the dirt in my house didn’t save my kids. And *why* are autoimmune disease rates increasing at a more rapid rate *every single year*?? Are kids really getting more hygienic by the month? Not the kids I know….
The gut dysbiosis that is linked to auto-immunity has to be coming from more than the amount of playing in dirt, which newborns have tended not to do at any age. We all know that antibiotics are important, but pollution cannot be held blameless. Why are animals in their natural habitats also suffering from immune dysfunction? And why does the rapid increase of fire retardants in our environment suspiciously mirror the rise of autoimmune disease? Suggested books: The autoimmune epidemic, and Our Stolen Future
No one is suggesting that the hygiene hypothesis is the sole cause of the increase in autoimmunity, allergies and asthma. As always, disease is multifactorial.
What about the schizophrenia and cat hosted organism connection ?
This article makes me sad. I grew up on formula, chronic antibiotics, and then tetracycline as a teenager. I now have constant inflammation and pain despite having been on a paleo diet for a decade (before I even heard of such a thing).
I’m presently on GAPS and feeling a liitle blue and defeated (I’m sure some of that is the serious need for more carbs but it’s not allowed right now). Does this mean there’s no hope?
tara – there’s always hope. Im not sure if you have someone guiding you, but I found a paleo minded nutritionist in my area who did extra testing to look at deficiencies and guide me. It helped. We determined that I was zinc deficient and not digesting eggs well. I added zinc, hemp hearts and brewers yeast. I am eating stir fries and leftovers for breakfast. Try to find a partner or someone to guide you. Look for new recipes too. Good luck!
I agree with Jennifer that there is always hope. I was in a similar situation as you minus tetracycline. We did GAPS for many months and still follow a paleo diet. I felt better but was still off. Discovered we have a pyrolles disorder which means we leak zinc and B6. Wow, correct supplementation has changed my world! And my son’s too. We’re still working on getting his doses right as he grew a half foot in a year.
I have been without hope at times too. I’m now 45 and feel the best I’ve felt in my entire life. Healing takes time. Our bodies change and we need to adjust. Yes, there is hope!
I too have pyroluria. It can take quite some time to resolve the copper:zinc imbalance and restore B6 status but it is well worth it. My immune system is amazing after having been previously DXed with igG1 and 3 subclass deficiencies. There is a Pyroluria support group on Facebook which is a wonderful group: https://www.facebook.com/groups/pyroluria/
I have pyroluria too. It was a god send being diagnosed, but my health is still suffering. Please let us know what you do for it.
Excellent article. Though sadly, I grew-up in a fairly dusty household, I played in the dirt, and I still have an autoimmune disorder! Of course the reasons for it are far more complex than dirt.
Another thing I wanted to add is that in the very first hours of life are when a babies gut flora inhabits it’s body from the outside. That is why it’s recommended that the mother not wash her breasts before the infant is skin-to-skin. But obviously, if one is in a hospital environment the baby will also be ‘infested’ (I guess you might say) by the random bacteria that is in the hospital, especially if the baby is not skin to skin immediately after birth. I can’t help but think this isn’t healthy. The ideal thing would be for the baby to be at home around it’s familial bacteria immediately after birth.
Speaking of eating dirt…
I have always wondered your position on using bentonite clay and zeolite clay for detoxification purposes(and maybe other benefits?) …Geophagy (http://en.wikipedia.org/wiki/Geophagy) has been practiced by indigenous groups for hundreds of years. Does this practice still have a place for individuals today?
Well,eating SCD for 16 months now for an IBD has proven to me that gut flora not only adjusts over time, but reduces and then eliminates IBD symptoms along with constantly changing up tolerable/intolerable foods. Now I’ve stabilized (perhaps, as more time on SCD will tell) as even sporatic stresses are without IBD symptom return. SCD protocol requires PROBIOTICS. Rush SCD and UMass SCD diet-like studies seem to confirm gut flora change with many reducing medications.
I totally encourage my kid to play in the dirt and I NEVER make her wash her hands before eating, either. She’s one of the healthier kids I know – no allergies, skin problems or anything and few colds, despite basically every family member on her dad’s side suffering from some form of eczema and multiple allergies (food and environmental). And yes, I do a lot of laundry, but it’s worth it.
I played in the dirt a lot when I was little too, and hand-washing before meals wasn’t part of my childhood. I’m not perfectly healthy, but at least I don’t have any auto-immune stuff going on, nor do I have food allergies, eczema or other skin conditions, depression, or anything else. I’ve had the flu only once and when I get a cold it lasts a few days and is rarely incapacitating (except when I need a bit of a “vacation”). So my admittedly small sample size and non-rigorous methodology totally supports the hygiene hypothesis 🙂
Count your blessings, lady. Sounds like you just got lucky. I also encourage my child to play in the dirt and also we lead a healthy lifestyle, eating locally grown organic foods etc. Sadly that did not do anything to protect her from multiple allergies, despite the fact that allergies do not ran in our family. No one knows what causes allergies, hygiene hypothesis is just a hypothesis not a proof of anything.
So excited to see you talk about this! I’ve been reading about this for a while. Check out http://www.hygienehypothesis.com, where they give good research references and talk about helminthic therapy.
Good article Chris. Another significant reason could be that we are actually disconnected more from the “dirt” and “ground” in modern society…
Most people (children included) spend their lives insulated from the healing powers of the earth…
If you haven’t heard of “Earthing”, you must look into it. Perhaps the most important recent health discovery…with the science to back it up!
Have you been reading Paleohacks? Big long convoluted discussion of all this over there. I find it fascinating. Do you think drinking kefir and eating fermented, traditionally prepared foods like sauerkraut can do anything to help us restore and/or maintain a better gut microbiome balance, or are we just screwed if we didn’t get the right birth and enough dirt as kids?
No, I never read Paleohacks. I’ve been interested in the hygiene hypothesis for some time, and I did helminthic therapy myself when I believed I had Crohn’s disease earlier on. I’ve also talked a lot with Kurt Harris about it, and he’s done tons of research on that subject lately. Hence the timing.
Chris, those of us in the helminthic therapy community are some of your biggest fans! My son and I are regaining our health by going back to our evolutionary roots, including a paleo diet and helminthic therapy. We also consume a pinch of dirt when we visit our favorite organic farm to pick up our produce. A little dirt never hurt. I always make time to visit the farm since my son has a rare disease called eosinophilic esophagitis, and living in an apartment is a pretty sterile life, no way to heal from this devastating disease. In fact, I read an article recently that said our microbiomes are more like lab rats than wild rats, and there is known to be differences in the immune system of those two populations of rats.
I would love to hear more about your adventures with helminthic therapy. I have decided I will keep a few (not too many) of my “old friends” necator americanus for the rest of my life.
I just read that your son has eosinophilic esophagitis…
So do I. I also have oral allergy syndrome and GERD. I have been on a daily PPI (rabeprazole) for over 5 years and still these issues persist.
My conditions developed when I was away from home at University living in an old, dusty student house (with a moldy basement). I was also making poor lifestyle choices (drinking, and smoking cigarettes & marijuana). I believe all of these factors, put my body in an inflammatory/allergic state and promoted disease processes. That said, I did have many environmental allergies when I was younger, as well as asthma.
I am, finally, completely reforming my diet in attempts to resolve these issues. And I want to discontinue my daily PPIs. Today is day 1. After reading some of Chris Kresser’s articles I have decided to start with a low FODMAP, low carb, and paleo diet (as well as avoiding foods that I am allergic to) and will soon be implementing food sources/supplements to help rebuild a healthy gut flora and induce increased stomach acid secretion (Chris has an article that GERD is likely caused by low levels of stomach acid).
As you know, there are very few people with this condition. I would love it if you had any advice or helpful information on changes that your son has made in his life that have given him relief.
Advice that I have: see an allergist to identify foods which cause inflammation of the oropharynx, Yoga has been very helpful in promoting proper digestion (Hot Yoga specifically), and daily exercise. Furthermore, the following advice seems basic but it is essential and I was embarrassed when I realized how effective it was: be as calm as possible at meal times, give yourself a lot of time to eat, chew your food slowly and many times, and avoid talking while eating. I strongly believe that EE (for me) has roots in worry, anxiety and stress. Perhaps this is another reason that Yoga has been helpful.
I’ve almost given you my life story now. I am in a strong, pro-health, independent and goal-oriented state of mind at this point in my life. I would love to hear of other’s pursuits and will gladly share mine. Feeling good and living healthy are my new top priorities.
I too have eosinophilic esophagitis. I don’t think it’s rare at all. I figured out that wheat/gluten is what causes it for me. No gluten = no choking on my food! Good Luck with your son!
I am also hosting necator americanus and it has helped a lot with asthma & food allergies. Here’s a forum on FB to discuss HT for those who are wanting to learn more: http://www.facebook.com/groups/htsupport/
I’m hosting Necator americanus and have had huge benefits with a whole slew of health problems, including Crohn’s, food intolerance, allergies, CFS and Restless Leg Syndrome. Truly amazing! http://tiny.cc/elc9bw
I’m glad my kids grew up on a hobby farm and were exposed to more dirt than city kids typically are. They dug clay out of the pond to create things and when they needed a snack they grabbed a carrot out of the garden, gave it a wipe on their jeans and ate it. My older son, the gourmet, used to pick meadow mushrooms and saute them in our own farm butter for a snack.
George Carlin has known this for years : http://www.youtube.com/watch?v=X29lF43mUlo
Loved your clip! Thanks for sharing!
That was hilarious!
Classic Carlin WINNING!
As a mom with MS, thie makes total sense! Kids that live on farms, are the healthiest I know!
If my Dr’s had the common sense 10 years ago when my stomch problems started, to tell me about Paleo, consider Leaky Gut… I really think I wouldbe much better off today. 10 days on Paleo Autoimmune has made a big difference already!! Thank heavens I picked up Robb’s book! Can you tell us why no nuts and seeds on autoimmune?
Thanks for your fabulous insights!
PS I am using your meal planner and it is making life so easy!!
I would like an answer to this also.
It’s interesting to see studies that prove our germaphobic culture is doing the opposite of what is intended–to avoid illness. An article I read recently discussed how cow manure contains beneficial bacteria that boosts serotonin production–vacca something-or-other–and this may be a reason why gardening has such a calming effect.
Also, maybe this is part of the reason why earthing is so effective. Not the mats, obviously, but walking barefoot outside.
Thanks for this great read! I do love gardening with my children, and I was first made aware of the importance of “dirt” for our health after reading Jordan Rubin’s “The Maker’s Diet” back in 2004. This is why I never miss a day taking Garden of Life’s Primal Defense. Between the probiotics and the HSO’s (homeostatic soil organisms) it made a remarkable difference in my digestive health.