What is oolong tea good for? Benefits, evidence and whether it is good for you

Strong = multiple human trials or a meta-analysis. Moderate = a few small trials. Preliminary = early, traditional or animal data.

1. 1

   Raises energy expenditure and fat oxidation

   Moderate evidence

   In a controlled metabolic-chamber study, 12 men drinking full-strength oolong (about 1.5 litres a day) for 3 days burned 2.9% more energy over 24 hours (around 67 kcal) and oxidised 12% more fat than when drinking water, with the effect greater than caffeine-matched water. A Japanese crossover trial in 11 women found oolong raised energy expenditure by about 10% for 2 hours after drinking, more than green tea at 4%.

   Key evidenceRumpler et al., Journal of Nutrition 2001; Komatsu et al., Journal of Medical Investigation 2003.

2. 2

   Helps with modest weight and waist loss

   Moderate evidence

   In a 6-week Chinese trial, 102 overweight or obese adults drank oolong brewed from 8 g of leaf a day: 64–70% lost more than 1 kg and 22% lost more than 3 kg, with reduced waist circumference and subcutaneous fat, and the effect was stronger in those who were heavier at the start. The trial had no control group, so some of the loss may reflect being watched; the metabolic-chamber data make the direction plausible.

   Key evidenceHe et al., Chinese Journal of Integrative Medicine 2009, 102 adults, 6 weeks.

3. 3

   Lowers blood glucose in type 2 diabetes

   Preliminary evidence

   In a crossover trial, 20 people with type 2 diabetes on oral medication drank 1.5 litres of oolong a day for 30 days: average plasma glucose fell from 229 to 162 mg/dL and fructosamine (a 2–3-week glucose marker) dropped from 410 to 323 µmol/L, both reversing in the water period. It is one small trial at a large daily volume, so treat it as promising, not proven.

   Key evidenceHosoda et al., Diabetes Care 2003, 20 adults with type 2 diabetes.

4. 4

   Improves eczema (atopic dermatitis)

   Preliminary evidence

   In an open study at a Japanese dermatology clinic, 118 adults with treatment-resistant atopic dermatitis drank 1 litre of oolong a day (from 10 g leaf) alongside their usual care; 63% showed marked to moderate improvement after one month, with effects beginning in the first 1–2 weeks and persisting in 54% at six months. Without a placebo group it cannot be called proven, but the size and speed of response are notable.

   Key evidenceUehara et al., Archives of Dermatology 2001, 118 patients, 6 months.

5. 5

   Improves cholesterol particle quality and adiponectin

   Preliminary evidence

   Twenty-two patients with coronary artery disease who drank 1 litre of oolong a day for a month had higher adiponectin (a protective hormone), larger LDL particle size and lower HbA1c than during a water month, though total LDL did not change much. Taiwanese cohort data link habitual oolong drinking with lower cholesterol, and tea catechins lowered LDL by about 4.6 mg/dL in green tea trials.

   Key evidenceShimada et al., Diabetes Research and Clinical Practice 2004, 22 patients, crossover.

6. 6

   Sharpens attention and mood

   Strong evidence

   Each cup supplies 30–50 mg of caffeine and about 5–10 mg of L-theanine, the pairing that improved attention switching and reduced distraction within an hour in placebo-controlled trials at 40–100 mg of each, while theanine moderated caffeine's blood-pressure rise. The evidence is for the compounds rather than oolong specifically, but oolong delivers them at a mid-range dose.

   Key evidenceHaskell et al., Biological Psychology 2008; Owen et al., Nutritional Neuroscience 2008.

7. 7

   May support bone density

   Preliminary evidence

   In a Taiwanese study of 1,037 adults, those who had drunk tea (mostly oolong and green) habitually for 10 or more years had bone mineral density about 6% higher at the hip and spine than non-drinkers, after adjusting for weight, exercise and smoking. The link held only for long-term drinking and may reflect fluoride, polyphenols or lifestyle differences; no randomised trial has tested it.

   Key evidenceWu et al., Archives of Internal Medicine 2002, 1,037 adults.

8. 8

   Protects teeth from decay

   Preliminary evidence

   Oolong's polymerised polyphenols strongly inhibit the glucosyltransferase enzyme that Streptococcus mutans uses to build plaque, and in small Japanese studies rinsing with oolong extract reduced plaque deposition over several days. Oolong also contains fluoride. These are mouth-rinse and laboratory studies rather than trials of drinking the tea.

   Key evidenceOoshima et al., Caries Research 1994 (plaque-inhibition study).

Is oolong tea good for you?

• Yes for most adults: 2–4 cups a day gives a mild metabolic lift, catechins and theaflavins for the heart, and mid-range caffeine with L-theanine for focus.
• The weight and blood-sugar trials used large volumes (1–1.5 litres a day) and were short or uncontrolled, so expect a nudge of 1–2 kg over months, not a transformation.
• Drink it between meals if you are iron-deficient or vegetarian; like all true teas, it reduces non-heme iron absorption from food eaten with it.
• Keep it to 2–3 cups in pregnancy (under 200 mg caffeine), stop by mid-afternoon if you sleep poorly, and choose lighter steeps if you have reflux.

• Rinse the leaves with a 5-second splash of hot water and discard it; it wakes the rolled leaf and softens the first steep.
• Good oolong improves over the second and third steeps, so never throw the leaves out after one cup.
• Tea bags labelled oolong are often broken dark leaf; whole-leaf Tie Guan Yin, Dong Ding or Wuyi rock teas are a different drink.

Frequently asked questions

1. Rumpler W, Seale J, Clevidence B, et al.. Oolong tea increases metabolic rate and fat oxidation in men. Journal of Nutrition (2001)
2. Komatsu T, Nakamori M, Komatsu K, et al.. Oolong tea increases energy metabolism in Japanese females. Journal of Medical Investigation (2003)
3. He RR, Chen L, Lin BH, Matsui Y, Yao XS, Kurihara H. Beneficial effects of oolong tea consumption on diet-induced overweight and obese subjects. Chinese Journal of Integrative Medicine (2009)
4. Hosoda K, Wang MF, Liao ML, et al.. Antihyperglycemic effect of oolong tea in type 2 diabetes. Diabetes Care (2003)
5. Uehara M, Sugiura H, Sakurai K. A trial of oolong tea in the management of recalcitrant atopic dermatitis. Archives of Dermatology (2001)
6. Shimada K, Kawarabayashi T, Tanaka A, et al.. Oolong tea increases plasma adiponectin levels and low-density lipoprotein particle size in patients with coronary artery disease. Diabetes Research and Clinical Practice (2004)
7. Wu CH, Yang YC, Yao WJ, Lu FH, Wu JS, Chang CJ. Epidemiological evidence of increased bone mineral density in habitual tea drinkers. Archives of Internal Medicine (2002)
8. Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB. The effects of L-theanine, caffeine and their combination on cognition and mood. Biological Psychology (2008)
9. Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. British Journal of Nutrition (1999)
10. U.S. Food and Drug Administration. Spilling the Beans: How Much Caffeine is Too Much?. FDA Consumer Updates (2024)View source