All carbs are not equal. Since Robert Atkins most low carb gurus have argued that the danger in carbohydrates lies in their sugars. In 2004 Dr. Alessio Fasano discovered zonulin. Zonulin's significance is still misunderstood in mainstream medicine.
When we eat volatile sugars like fructose and sucrose they grow harmful microorganisms in the small intestine. Given time the intestinal immune system starts responding with zonulin. Zonulin defeats the "tight junctions" between the cells lining the small intestine. It causes permeability, and allows the digestive lumen to pass into the bloodstream before being thoroughly digested. When we ingest proteins like the gluten in wheat and the casein in milk, the digestive immune system mistakes them for harmful digestive microorganisms. The gut responds with permeability, and dumps the lumen into the bloodstream.
Unfortunately many of the partially digested proteins are opiates. They mimic body proteins, and wreck havoc. The zonulin dump and metabolic responses are age related. For the most part infants are born without a zonulin problem. Zonulin permeability and metabolic responses become prevalent. Over the lifespans of humans the reactions are nearly universal, but differ in severity.
Dr. Jack Kruse is running a series of articles describing zonulin permeability, the autoimmune and metabolic consequences, the universality of response, and his theory about an evolutionary explanation.
Dr. William Davis wrote a book about wheat's contribution to these diseases and conditions: