The term leaky gut refers to a part of the intestinal tract, stomach, small intestines, that becomes permeable due to exposure to a virus, bacteria, parasite, stressor, chemical, environmental toxin. Once permeable the immune system becomes involved in trying to rid the body of the stressor by producing antibodies and cells that fight their battle. The immune system may make antibodies that cant tell the difference between healthy tissue and the offending agent ( as in the case of Celiac autoimmune disease to gliadin, a protein in wheat, rye, barley ).
What people might not be aware of is cross reactivity.
Cross reactivity means that eating one food can cause a response similar to eating another
cows milk is known to cross react to gluten in grains
Whey protein is known to cross react to rice
Chocolate milk is known to cross react to corn
casomorphin in milk is known to cross react to oats
alpha and B casein in milk is known to cross react with yeast
This is why when a person has a leaky gut, initially it is best to stay away from milk and wheat products, since a permeable intestines may cause milk and wheat proteins to enter the blood and cause inflammation from their proteins.
Its best to wait until the initial insult and the leaky gut has been resolved.