"Leaky Gut", which is a term I heard 20 years ago, was never seen in the medical literature until fairly recently. The fact that it is now acknowledged is going to help with understanding the cause of many "medically unexplained symptoms" and also diseases, such as autoimmune diseases and allergy:
Leaky gut may be a cause of both type 1 and type 2 diabetes:
It may be a primary cause of weight gain:
What is leaky gut? It is a subtle permeability of the small intestine wall in which bacteria, undigested food particles and toxins pass through the gut wall into the bloodstream. This should never happen, so when it does, it causes the immune system to create antibodies and pro-inflammatory substances (cytokines) that can cause many symptoms. It also overburdens organs such as the liver, which has to deal with the toxic byproducts of bacteria-induced leaky gut:
What causes leaky gut? Microbial imbalances (certain bacteria, parasites, yeast overgrowth) may be a primary cause, and these imbalances may be caused by antibiotics and steroid medications. Excessive starch consumption, by creating hydrogen gas, may cause small intestine bacteria overgrowth (SIBO). Food sensitivities can be caused by leaky gut and may be a cause themselves.
The take home message is this: Leaky gut may be a true causal factor behind many seemingly unrelated symptoms and even diseases.