In a recent analysis of 199,794 participants studied for over 20 years in the Nurses Health Study (NHS II) and Health Professionals Follow-Up Study (HPFS), those with the highest consumption of gluten had the lowest levels of type 2 diabetes. 
My recommendation:Unless you have a compelling reason (such as celiac disease) to avoid gluten, I recommend including minimally-processed whole grains (whole wheat, rye berries, whole hull-less barley, etc.) in your diet on a daily basis. The health benefits are inescapable; don’t get caught up in the gluten-free fad! However, I suggest avoiding products with ingredient lists that include added gluten, which always refers to refined gluten; naturally-occurring gluten will not be on the ingredient list. To read more about gluten see pages 40-41 of Good Food, Great Medicine (3rd edition). We talk about the health benefits of eating whole grains on pages 23-25 and why we all should avoid highly-refined grains on page 46.
Miles Hassell MD