When my son Marty was born, I wanted him to love the world. For a while, he did. He was quick to smile. He hugged dogs. He sprinted to school. “Marty is so engaged and well-behaved,” his teacher said.

Problems in the gut causing glitches in the brain When Marty ate gluten (a protein in wheat, rye, and barley), his digestive system reacted like it was poison. Immune cells attacked and created ...