In 1994 I was diagnosed with celiac disease, which led me to create Celiac.com in 1995. I created this site for a single purpose: To help as many people as possible with celiac disease get diagnosed so they can begin to live happy, healthy gluten-free lives. Celiac.com was the first site on the Internet dedicated solely to celiac disease. In 1998 I created The Gluten-Free Mall, Your Special Diet Superstore!, and I am the co-author of the book Cereal Killers, and founder and publisher of Journal of Gluten Sensitivity.
The connection with wheat (and rye and barley) wasnt recognized until the 1950s - (a)nd it wasnt until the 1960s that intestinal biopsies began to become commonly used in the diagnosis of celiac disease. With regard to the harmfulness of barley malt, the situation is complicated. I will give you my best shot with the qualification that the ideal experiments have not been done and a definitive statement is not possible at this time.
Because barley malt is made from barley grain that has been germinated it is reasonably certain to be less toxic than barley itself. The hordein proteins and starch in the endosperm of barley grains, like the equivalent gluten proteins and starch in wheat, are there for storage purposes. In a sense, they provide food for the new plant upon germination. In order to use the hordein proteins, the grain releases and generates enzymes upon germination that break down the storage proteins into their constituent amino acids. The problem is that the process is not complete during a short germination, so some peptides (short pieces of the proteins) remain intact in malted barley. There is experimental evidence for this. The resulting mix of peptides is highly complex.
We know from work described in the scientific literature that relatively small polypeptide chains can still retain activity in celiac disease and we know something about a few sequences that seem to be harmful. But we probably dont know all the sequences that are harmful and we havent put our fingers on the common theme that gives rise to the activity in celiac disease. So the question arises as to whether or not the remaining sequences in malted barley are harmful.
The possibilities that come to my mind are:
There is no completely solid evidence for or against there being a threshold of gluten consumption below which no harm, or at least no lasting harm, occurs and above which definite harm occurs (but see my previous post to the list on starch/malt question). This is a difficult area to study where zero consumption is being approached and the arguments that come up are at least similar to those that have arisen in regard to the question of whether or not there is a minimal level of radiation exposure below which no harm is caused, but above which there is harm that increases with dosage. Accordingly, celiac patients must choose arbitrarily the path they feel comfortable with.
Here are some references that deal with the question of peptide toxicity. It is not a simple situation: