While only 2 percent of all tea consumption worldwide is from oolong tea, this wonderful tea deserves more attention. It has been linked to benefits such as increasing metabolism. This delicate, sweet and smooth tea has been around since the 16th century. If you try it, you may notice that the leaves have a unique appearance. Oolong tea is made using a fermentation and oxidation process that gives the leaves a yellow surface with a reddish edge.