Oolong Tea

What is oolong tea?

Oolong tea comes from the same plant as green and black tea, Camellia sinensis. What sets it apart is processing: the leaves are partly oxidized, placing oolong between unoxidized green tea and fully oxidized black tea. It is traditional in southern China and Taiwan. Oolong contains caffeine, catechins such as EGCG in smaller amounts than green tea, and theaflavins and other polyphenols formed during oxidation.

What the research says

Energy expenditure

The most rigorous human study measured metabolism in a sealed room calorimeter. Twelve men drank full-strength oolong tea, half-strength oolong, water or water with caffeine for three days each. Compared with water, full-strength oolong raised 24-hour energy expenditure by 2.9%, about 67 calories a day, and increased fat burning by 12%. Caffeinated water raised energy expenditure by a similar 3.4%, which suggests caffeine explains much of the effect (Rumpler et al., 2001). The full-strength tea was brewed from 15 grams of leaves a day and served as five 300 mL cups, much more than a single tea bag.

Body weight

In a Chinese study, 102 adults with overweight or obesity drank tea made from 8 grams of oolong a day for six weeks. Most lost more than 1 kg, and people with high blood lipids saw lower triglycerides and cholesterol (He et al., 2009). However, the study had no control group, so it cannot show that the tea caused the changes.

For tea in general, NCCIH says the catechins and caffeine “may have a modest effect on body weight,” and that results vary with the product and a person’s activity level (NCCIH: Green Tea). Much of that research is on green tea, but oolong shares the same main active compounds.

How it’s used in supplements

Oolong is usually consumed as brewed tea and sometimes appears in weight loss teas and extracts. Studies with measurable effects used several cups a day. An 8-ounce cup typically supplies a moderate amount of caffeine, generally less than coffee.

Safety

As a beverage, tea is considered safe for most adults. The main concerns relate to caffeine: jitteriness, trouble sleeping, faster heartbeat and stomach upset, especially with several cups a day or in sensitive people. Concentrated tea extracts, rather than brewed tea, have been linked to rare liver injury, and green tea extracts can raise blood pressure and interact with nadolol, atorvastatin and raloxifene (NCCIH: Green Tea). People who are pregnant, have heart rhythm problems or anxiety, or take stimulant medications should limit caffeine and talk with their doctor about tea-based supplements.