The Grain Brain hypothesis states that the consumption of gluten (and grains in general) produce long-term neurological damage. It's been proposed and popularised by neurologist and best-selling author David Perlmutter. He's has now made a career as a diet celebrity, selling books, food products, retreats, and the like.
There is a very comprehensive critical review of his profile and ideas here, which basically states that the current (2015) evidence is not there to support his claims, but doesn't deny some potential plausibility. A similar conclusion is reached in this Quora question, from 2014.
I wonder what's the updated case for or against that hypothesis. I did a rough search on Google Scholar and found this and this articles advising against low or gluten free diets. This one suggests gluten might not have to do with mild brain degeneration. This meta-analysis is too technical for me to understand but seems to focus only on those allergic to gluten.
Anyone aware of the most recent and reliable evidence on this hypothesis?