@T-3 I don't know why Ray preferred nixtamalized corn, and didn't find the answer easily in search.
From what I've read elsewhere, it's the gluten, and in the case of corn and popcorn other gluten-like proteins, that cause the digestive issues.
Ray liked the polyphenols in orange juice particularly. The ferulic acid in popcorn and other grains is also in orange juice, but I don't remember that being the one he liked in orange juice.
I'm sorry I'm not one of the experts.