What it is
Wheat and its cousins with bran and germ intact — genuinely more food than white flour. But "whole grain" on a package rarely means it got the processing the grain needs.
Why your biology objects
Cereal grains are a ~10,000-year-old food — recent enough to still carry their seed defenses. Wheat brings wheat germ agglutinin (a lectin) that binds the gut lining, phytic acid that chelates zinc and iron, and gliadin, which triggers zonulin release and loosens the gut wall's tight junctions. Your ancestors didn't eat grain raw — they soaked, sprouted, and sourdough-fermented it, and that processing (phytase, fermentation) is what stood the defenses down. The pot for beans; the starter for grain.