Compounds in Green Tea Can Improve Brain Function and Make You Smarter. Green tea does more than just keep you awake, it can also make you smarter. The key active ingredient is caffeine, which is a known stimulant. ... It also has the amino acid L-theanine, which is able to cross the blood-brain barrier · Green Tea Contains Bioactive Compounds That Improve Health · Compounds in Green Tea Can Improve Brain Function and Make You Smarter · Green Tea Increases Fat Burning and Improves Physical Performance · Antioxidants in Green Tea May Lower Your Risk of Some Types of Cancer · Green Tea May Protect Your Brain in Old Age, Lowering Your Risk of Alzheimer's and Parkinson's · Green T...