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WTF are Post-Biotics?

Updated: Mar 6


Prebiotics, probiotics, postbiotics. What's the difference, and should you care?  A lot of media attention has been given of late to the "bugs" that hang out in your pipes.  Is it all hype, or the next miracle health discovery?  Well, maybe some of both....Studies are exploding as we begin to better understand the previously unexplored terrain of the alien ecosystem that is our insides.  We are learning that the health of our gut has much bigger consequences than GI symptoms, like gas, diarrhea, and constipation.  It turns out that over half of our immune system is located in our intestines.  What?!?!  Yes, you heard me correctly!  And the critters that cultivate our inner landscape are the primary "deciders" of how well this part of defense is able to function (other factors also play a role, such as medications that alter your pH).  Not only that, but we are also finding out that the gut microbiome, as it has been termed, even behaves like a second "brain," strongly impacting our mood and concentration, even our risk of developing neurological disorders, such as Parkinson's Disease. These microorganisms also produce vitamins essential to health, such as vitamin K critical to bone health and blood clotting, and B12 that helps us harness energy from carbohydrates, builds healthy red blood cells, and decreases homocysteine, a contributor to cardiovascular disease. 

So how do we make sense of the science? I'll try to summarize the key points you need to know:  Your GI tract is not just a tube.  It is a complex organ with layers of differentiated cells.  The innermost layer is called the mucosa.  It is composed of individual cells lined up side-by-side like soldiers defending a city. These cells do their best to communicate to one another through a complex array of chemical mediators in an effort to regulate which substances get absorbed and which either get passed through as waste or need to be further broken down.  The spaces between these cells are called "tight junctions."  When large molecules pass between these gates that are supposed to be kept out, our body's defenses go on hyper alert.  This can cause food allergies (when large food proteins pass through before they are able to be broken down into amino acids) and possibly even auto-immune syndromes (when our immune system goes into over-drive and starts attacking our own tissues).

It turns out that these mucosal cells need to be properly nourished in order to do their job properly.  What do they need to thrive?  Substances such as short-chain fatty acids that are produced when beneficial microorganisms living in our digestive tract metabolize substances that we can't, such as fiber.  This is one reason why fiber is so important in our diets.  It's not just "bulk."  The beneficial bacteria and yeasts depend on plant fiber for their fuel. Without sufficient fiber, they can actually turn against us by feasting on the gut lining itself, leading to its breakdown. Fiber that feeds the good bacteria is called pre-biotics.  And while it may help to some degree with motility issues, your grandmother's Metamucil won't cut it.  You need a variety of different types of fiber because you want to nourish a diversity of good guys in your gut.  This is your best shot to crowd out the bad guys that can cause infection and inflammation and to withstand the ravages of antibiotics, when you do need them.  Just like a crop of one type of plant is more susceptible to drought and pests, so your flora is the heartiest when it is more varied.


What about probiotics?  Do we need them?  So, here's the deal.  There is no evidence that commercial probiotic organisms actually take up residence in our intestines.  They likely pass on through.  However, for folks who have a gut lining that is seriously impaired, they can provide some benefit to the injured mucosal cells on their way out. 

Those who already have a fairly healthy zoo flourishing down there probable won't notice much benefit.  If you do decide to try a probiotic product, take a variety of strains, and take it slow, building up your tolerance for greater numbers of "colonies." 

If you overdo it, you may find yourself needing to quarantine in your bathroom.  The same goes with fiber. Some gas is a good sign that the little guys have plenty to eat, but if you are not used to lots of fiber in your diet, I recommend increasing the amount you eat gradually, as well as adding plenty of water to prevent

unwanted constipation.



A healthy microbiome is affected by many factors, some beyond our control, such as whether we were born vaginally or by C-section and whether we were breastfed or formula fed, as well as by medications, and even insecticides on our non-organic produce.  A big step we can take to foster its vitality is with post-biotic foods.  Huh?  Post-biotics are foods that have been naturally fermented, or anaerobically broken down by naturally occurring bacteria and yeast.  These foods are easier to digest and less likely to cause intolerance symptoms (because much of the hard work has already been done), contain easy-to-access micronutrients (i.e. vitamins and minerals), and boast unique substances that nourish our gut cells and the commensal organisms residing there.  Examples are sourdough bread (the carbohydrates and gluten are broken down and less likely to cause tummy trouble for sensitive individuals (though those with full blown celiac/sprue must still avoid it), yogurt and kefir, miso, kimchi, kombucha, sauerkraut, and other lacto-fermented vegetables. 


Overwhelmed?  Don't be.  A healthy GI tract and therefore optimal immunity and energy can be achieved by taking small steps toward nourishing your gut microflora.  You've got this.


Amy B. Toscano, RDN, CFMHC

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