Oolong tea is a traditional Chinese tea made leaves and buds of Camellia sinensis plant; the same plant that is used to make green tea and black tea. Though made from the same plant, the oxidation level resulting from different production style makes one tea different from another.
Green tea is unoxidized, black tea is fully oxidized whereas oolong tea is partially oxidized giving it a unique taste. The taste of oolong tea can also differ (sweet, bitter or grassy) depending upon the horticulture and degree of oxidation allowed during production.
Nutrients in Oolong Tea
Oolong tea contains powerful antioxidants because they are not completely fermented. It also contains several vitamins, minerals and useful chemicals.
|Nutrients in Oolong Tea|
|Minerals||Calcium, Manganese, Copper, Selenium, Potassium, Zinc|
|Vitamins||A, B, C, E, K|
|Other Chemicals||Folic acid, Niacin amide, Caffeine, Theophylline, Theobromine|
Benefits of Oolong Tea
Along with it's unique taste, oolong tea also provides several health benefits. As it is packed with powerful antioxidants, it helps to prevent cancer, improves mental alertness, prevents heart disease, makes bone strong and so on.
Health Benefits of Oolong Tea
Fights free radicals and boosts immune system
Oolong tea can fight against free radicals, improves immune system and may prevent diseases like cancer. Oolong tea contains polyphenol, a powerful antioxidant, which reduce cell damage and fights against free radicals without damaging the healthy cell. Besides, the potent catechin called epigallocatechin gallate (EGCG) helps to fight against allergies. [1, 2]
Improves mental alertness and reduces stress
Along with caffeine, teas like green tea and oolong tea also contain l-theanine, an amino acid. Caffeine is a natural stimulant which promotes activities of central nervous system. However, high intake of caffeine might result in hype and anxiety which are prevented by the l-theanine, the stress reducing agent. These compounds as a pair help to improve overall brain function and mood. [3, 4]
Promotes weight loss
Polyphenols in oolong tea blocks absorption of fat from diet. As a result, drinking oolong tea in considerable lifestyle can help reduce the body fat. In addition, drinking oolong tea also improves lipid metabolism, thus prevents you from possible coronary artery diseases that arise with obesity. 
Treatment of diabetes
According to a study, oolong tea lowers the plasma glucose levels in person who have type II diabetes. Also, it was found that, drinking oolong tea and anti-diabetic medication in conjunction was more effective in lowering glucose level than when drug was used alone. 
Strong bones and prevents tooth decay
There are several minerals found in oolong tea including calcium and magnesium. Regular consumption of oolong tea for long period of time, especially more than 10 years, has significant benefit on Bone Mineral Density (density of minerals in bone) in adults.
Oolong tea extract can significantly lower plague deposition which prevents the decaying of tooth. Moreover, randomized trials even suggest protective effect of polyphenols in oral lesions and cancer. 
Beauty Benefits of Oolong Tea
The primary factors of aging are free radicals and oxidative stress. Oolong tea can fight against both these factors as it possesses powerful antioxidants. Dying skin cells are rejuvenated and signs of aging such as wrinkles, fine line, dark spots, uneven skin tone, sagging skin, etc can be eliminated with regular consumption of tea containing polyphenols. 
How much oolong tea should you drink?
Oolong tea contains caffeine as much as 37 mg per 8 fl. Oz. cup. And 400 mg of caffeine a day is considered safe for healthy individuals.
However, health experts suggest limiting your daily tea consumption to no more than 5 cups in a day to avoid any possible consequences of caffeine overdose. Also, it would be a good idea for you to consult physician beforehand you decide your safe caffeine limit.