Ever wonder if your home brew is as strong as a cuppa Joe from Starbucks? You may be able to test your coffee’s kick with the shine of a light: Scientists in Korea and Singapore have created a kit called Caffeine Orange that lights up your drink with a non-toxic laser to let you know when you’ve got too much caffeine in your cup.
While red usually signals to stop, healthy adults can drink up to 400 milligrams (mg) of caffeine a day—about 4 cups of coffee—without negative effects like headaches, drowsiness, anxiety, and nausea, according to a recent study in the Journal of Food Science. How we metabolize caffeine varies by gender, weight, and genetics, but if you’re having trouble sleeping or feel jittery, it’s time to cut back. Until Caffeine Orange is available to buy, use this guide to judge how much boost is in your bottle.
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