Elevated zonulin levels in the gut have been linked to elevated zonulin levels in the brain. Translation: A leaky gut can lead to a leaky brain. Once the blood-brain barrier has been breached, your brains immune system — glial cells — can be activated. Glial cells will then cause inflammatory cascades throughout the brain. (I cover this topic in more detail in Signs You Might Have A "Leaky Brain" + What To Do About It.)