If you were to inject dye into your body, it would stain all of your organs except for your brain. If you were to inject dye directly into your brain, your brain would become stained but none of your other organs would!
This oddity is because of the blood-brain barrier. Within your brain the capillary endothelial cells are fitted together very tightly which makes the capillary wall nearly impermeable. The blood-brain barrier exists to keep foreign substances out of your brain and without it your brain would become toxic and you would become ill and then die.
The biggest threat to your blood-brain barrier is wheat germ agglutinin (WGA). WGA is a protein that can cross the capillary wall and enter your brain, frequently bringing other foreign substances along with it. This mechanism is thought to underlie many mood disorders like depression and anxiety as well as degenerative neurological illnesses like Alzheimer’s and multiple sclerosis.
WGA is found in wheat, of course, but the highest concentrations of WGA are found in whole grain wheat products. So why does the USDA recommend 3 ounces of whole grain every day? If they’re trying to start the zombie apocalypse they’re doing a great job.
Wheat’s effect on your blood-brain barrier is a physiological reality that trumps any silly food allegiances. Whether you’re paleo, vegan, or whatever – wheat kills your brain. Don’t eat it.