5. Green tea
Drink it for: The amino acid L-theanine
Examples: Hot green tea, brewed iced green tea — including flavored varieties like jasmine green tea or berry green tea
Why it helps: L-theanine is an amino acid found mainly in tea leaves; it’s been shown by EEG tests to stimulate alpha brain waves. This can improve focus while also having a calming effect on the body.
“Despite the caffeine, the L-theanine in green tea seems to be profoundly relaxing, with effects that last up to eight hours,” Reardon says. L-theanine is easily absorbed and can cross the blood-brain barrier, adding to its effectiveness.