Caffeine cuts blood flow to the brain by 30%. Psychiatrist Daniel Amen says anything that lowers blood flow prematurely ages the organ. He founded Amen Clinics, which has performed over 200,000 brain SPECT scans. In his scans, low blood flow is linked to depression, ADHD, substance use problems and traumatic brain injury. He says it’s the top imaging predictor of Alzheimer’s. On SPECT, he says, caffeine constricts blood flow by 30%. The effect is large enough that he has patients avoid caffeine the morning of a scan. Otherwise it artificially lowers the reading. Blood flow is not his only reason. Caffeine blocks adenosine and disrupts sleep. It is addictive and causes withdrawal. It raises cortisol. His position: caffeine is best limited or avoided for optimal brain function. And the patients who quit tell him the same thing: “So many of my patients stop, and uniformly they tell me they feel better. They said their energy is better.” One of them was Jeff, a pilot with brain fog and memory problems. Jeff was having around 600 mg of caffeine per day (less than two Venti brewed coffees from Starbucks, at  ~330 mg each). His brain looked terrible. They cut his caffeine by 5% a day. In three weeks it was gone, with no withdrawal and no headaches. Then the texts from Jeff came in: “Unbelievable energy. Unbelievable clarity.” People treat caffeine addiction as one of life’s little miracles, with no cost. Amen’s scans tell a different story.