Leaky Gut: Facts and FadsThe latest fad of supplement makers is to talk about "gut health." The latest boogyman for the gut is the "leaky gut." The other name for leaky gut is intestinal permeability.A Surgeon's ViewAs a surgeon, a "leaky gut" is a devastating surgical emergency. Surgeons emergently operate to remove the gut that no longer has a barrier function.The dark gut is dead and needs to be surgically removed. This gut has no barrier function and will allow bacteria from the inside of the small bowel to easily enter the patient's bloodstream. Leading to septic shock and death.The Non-Surgical Emergency or Chronic Leaky GutBut a leaky gut doesn't have to be so dramatic.  Not leading to septic shock or needing to be removed. In this model, the intestinal barrier is "leaky," not to the point of causing sepsis. But the leaky gut enables small molecules to leak out of the gut into the bloodstream. Thus producing chronic inflammation.Chronic inflammation may cause obesity. Emphasis on "may."Emulsifiers and ObesityRodent studies have provided fascinating insights. Certain emulsifiers, when added to the diet of mice or rats, lead to obesity.  In one experiment, rodents were fed identical amounts of kibble. But one group, emulsifiers, was added to their water.  These emulsifiers, like polysorbate 80, not only produced obesity but also disrupted the microbiome of the gut (ref). But mice are not men.When dietary emulsifiers are examined in humans, high levels cause disruption of the gut. However, there is little evidence that small amounts found in the food supply cause issues. (ref 4)Non-Humans and Leaky GutWhile animal models are interesting, human studies provide useful information. That a rat or mouse has a leaky gut based on some intervention is not an equivalence in humans.Functional Medicine and Leaky GutIf you searched "leaky gut," you will find a host of "functional medicine" doctors providing supplements, bone broth, probiotics, and other scams.  On the shelves of drug stores and "health food stores," you will find abundant supplements to "support gut health."Disease States and Leaky GutFunctional medicine physicians associate many disease states with leaky gut. The following have little or no good evidence to be caused by a leaky gut:Alcoholic cirrhosisAsthmaAutismChronic fatigue syndromeDepressionEczemaEnvironmental enteropathyEosinophilic esophagitisFibromyalgiaKwashiorkorMetabolic syndromeMultiple sclerosisNon-alcoholic fatty liver disease (NAFLD)ObesityPancreatitisParkinson's diseasePsoriasisRheumatoid arthritisNon-Controversial Causes of Leaky GutThere is no doubt celiac disease, Crohn's disease, radiation, and ulcers from non-steroidal anti-inflammatory drugs; certain bacteria can cause a change in intestinal permeability (another name for leaky gut). Celiac disease and Crohn's disease have been studied for years (ref 2, ref 3). While we know gluten exacerbates the auto-immune function of those with Celiac disease, we do not yet have a mechanism for Crohn's disease.Gut Barrier Anatomy and FunctionThe small bowel's purpose is primarily for the absorption...