August 29, 2016
Hygiene hypothesis and the biome depletion theory.
I could not contain my excitement after reading a New England Journal of Medicine article (August 4, 2016) that Dr. Koontz put before me entitled "Innate immunity and asthma risk in Amish and Hutterite farm children".
A little context here: I have been preaching animal exposure for infants since the late 90's when I fell in love with caring for allergic and asthmatic children. Animal exposure and reducing allergy risk was a theory that made a lot of sense. I remember when Thomas was born in 2003, I would encourage my golden retriever, Nala, to lick him on the face all of the time to the dismay of my wife. The hygiene theory needed to be tested.
The NEJM study: The Amish and Hutterite communities are geno-centric populations that reside in tight nit farming environments where the only major difference was the exposure of the children to farm animal microbes. The Amish keep single family farms where the children play in the barns and around the animals. The Hutterites on the other hand have a more industrial based farming that keeps the homestead away from the farmed animals limiting the children's exposure to microbes. Both groups are known to keep an exceedingly clean domicile.
The authors set out to analyze the risk of developing asthma among 60 children from these two communities based on genetic ancestry, environmental exposure and immune profiles as tested. They measured the levels of allergens and bacterial endotoxin (cellular debris) of indoor house dust. They measured blood levels of allergic markers including IgE, inflammatory cytokines, gene expression patterns and white blood cell patterns. They also then went on to test the different groups dust on mouse models to recreate the perceived asthma and allergic sensitization effects.
What they found is astonishing! These two genetically similar groups had very different asthma prevalence outcomes. The Hutterites had a 6 fold increased risk of asthma and allergic sensitization. The Amish dust was found to be loaded with bacterial debris known as endotoxin at a volume 7 fold higher.
When they drilled down to the cellular level they found that the white blood cell proportions of the Amish children were dominated with neutrophils while the Hutterites had an increase in eosinophils known to be associated with allergic sensitization. Cytokine proteins that mediate inflammation were higher in the Hutterite children. Gene expression patterns noted that the Amish children had 18 unregulated genes that code for innate immune function and responses to microbial stimuli. This gene expression shift mediates the beneficial effects seen in the human cells.
The other beautiful piece of this experiment is the allergic mouse model. The authors gave these allergy predisposed mice the dust from both communities and found that the Amish dust exposed mice were protected from allergy sensitization by an upregulated innate immune system. The Hutterite dust exposed mice developed asthma.
The take home point: The innate immune system is primitive and wants to be challenged by microbes from birth. It is now clear from this study that by doing so, the immune system develops tolerance and avoids the unhealthy allergic reactions that we are faced with in many children today. Get dirty and expose your children to the dust of animals early in life.
Also do these things: 1) have a vaginal delivery if possible, 2) breastfeed, 3) avoid antibiotics, antacids and anti inflammatories like ibuprofen and acetaminophen, 4) eat an anti inflammatory diet with lots of fiber - prebiotic foods, 5) take probiotics