Organic Oolong Tea Leaf Oolong tea is a product made from the leaves, buds, and stems of the Camellia sinensis plant. This is the same plant that is also used to make black tea and green tea Mental alertness. Drinking oolong tea or other caffeinated beverages throughout the day seems to help maintain alertness and mental performance. Combining caffeine with sugar as an "energy drink" seems to improve mental performance better than either caffeine or sugar alone. Some research suggests that drinking oolong tea or green tea daily prevents developing high blood pressure. Drinking more tea seems to lower the even more. Obesity. Early research suggests that drinking oolong tea does not decrease body weight in overweight or obese people.