Data from Japan show drinking oolong tea may help your body burn fat, independent of the effects of caffeine. Around the world, tea is one of the most popular beverages, second only to water. In popularity, 84% of tea consumed is black; 15% is green; and the remaining 1% is split between oolong, white and dark teas.1
According to the Tea Association, total sales in 1990 were $1.84 billion, which rose to $12 billion by 2016.2 The market continues to grow, albeit at a slower rate, with reported sales of $12.67 billion in 2019. The Tea Association hypothesizes several trends could be affecting their industry, including a healthier outlook of consumers and a greater number of people who practice alternative nutrition such as gluten-free, dairy-free, vegetarian and keto diet plans.
On any day, nearly half the people in the U.S. are drinking tea, with a greater concentration of tea drinkers found in the South and Northeast. Although black tea is the preferred drink, it may be time to consider the less bitter and flavorful oolong tea.
A Cup of Oolong in the Evening Raises Fat Burning at Night
A recently published study from a team of researchers at the University of Tsukuba in Japan found that drinking oolong tea can help your body burn fat, even while you’re sleeping.3 The study took place over 14 days and engaged 12 non-obese men who drank either oolong tea, caffeine or a placebo at breakfast and lunch each day.
On Day 14, 24-hour measurements were recorded. The researchers found that drinking caffeine or oolong tea raised fat burning by approximately 20% without any effect on energy expenditure.4
However, they also found a greater decrease was experienced by those drinking the oolong tea suggesting there was an unidentified ingredient in the tea that has a greater effect on fat oxidation.5 Additionally, it appeared that the effect on fat burning was suppressed immediately after meals and occurred during sleep.
The researchers also found drinking two cups of oolong tea per day did not interfere with the participants’ sleep habits. Past research has demonstrated caffeine at greater than 100 milligrams (mg) can increase energy expenditure, but in the present study the amount of caffeine ingested did not increase energy expenditure.
This suggested to the researchers that the participants became tolerant over the two weeks of routine caffeine ingestion. While the researchers did measure fat burning, they noted two weeks was not a long enough duration to assess the effects this intervention could have on body composition. The senior study author commented in a press release:6
“Like all teas, oolong contains caffeine, which impacts energy metabolism by increasing our heart rate. However, studies suggest that tea consumption may also increase the breakdown of fat, independent of the effects of caffeine. We therefore wanted to examine the effects of oolong consumption versus caffeine alone on energy and fat metabolism among a group of healthy volunteers.
The stimulatory effects of oolong tea on fat breakdown during sleep could have real clinical relevance for controlling body weight. However, we need to determine whether the effects we observed in the 2-week study translate into actual body fat loss over a prolonged period.
In addition, we want to trial a decaffeinated oolong tea to better distinguish the effects of caffeine from other components of tea, which will help us understand exactly how oolong helps with fat breakdown.”
Green, Black or Oolong?
Although the health benefits of green tea are well covered, black tea is the most commonly consumed tea in the U.S. As the health benefits of oolong tea are not as well publicized, one team of researchers set out to assess how well a group of dental students understood the benefits of oolong tea.7
Using a set of questionnaires, they drew data from 100 participants using an online survey. Among the students, only 19% had ever heard of oolong tea, and of those only 55% were aware of the health benefits.
Interestingly, the Tea Association says that black, green, oolong and all dark and white teas are all made from the leaves of the same tree, an evergreen named Camellia sinensis.8 The difference in the taste and color happen when the leaves are processed. But, no matter which type of tea it is, or whether it’s caffeinated or decaf, it’s only 24 hours from the time tea leaves are picked until they’re packed.9
Before processing starts, the tea leaves are graded and sorted. The most common method of processing tea leaves is the Orthodox method during which the leaves go through four stages, including withering, rolling, oxidation and drying.
It’s in the oxidation stage that the color, taste and strength of the tea is determined. The leaves are laid out and left at 26 degrees Celsius (78.8 degrees Fahrenheit) for 30 to 120 minutes. During this time, oxidation occurs, which changes the color of the leaves.
The oxidation process is left out when making green tea, which gives the tea leaves a light fresh flavor. Black tea goes through the longest oxidation and oolong is made from partially oxidized leaves. The oxidation goal for tea leaves destined to become oolong is 70% green and 30% brown, enough to give a delicate color and fruity aroma.
The shape of the leaves and flavor of oolong tea can vary depending on where it’s grown and how it’s processed.10 For instance, oolong tea from Taiwan is traditionally less oxidized and the famous Chinese teas are grown in a harsh environment, which gives the leaves a rich flavor.
Oolong Shifts Salivary and Gut Microbiota
In addition to raising fat metabolism, oolong tea also has an impact on your oral and gut microbiota. One study, published in the journal Nutrients, evaluated the oral microbiota of three healthy adults who drank 1 liter (33 ounces) of tea daily for eight weeks.11 Before the intervention, during the treatment and after the study, the participants’ salivary microbiota were sampled, sequenced and analyzed. The data showed:12
“[O]olong tea consumption reduced salivary bacterial diversity and the population of some oral disease related bacteria, such as Streptococcus sp., Prevotella nanceiensis, Fusobacterium periodonticum, Alloprevotella rava, and Prevotella elaninogenica.”
The results suggested that drinking oolong tea for an extended period of time could change your salivary microbiota and have a protective effect on dental health. Several studies have also evaluated the effect oolong tea has on modulating human intestinal microbiota in the lab and in animal models.
One study published in Food Research International demonstrated the compounds commonly found in oolong tea, including epigallocatechin gallate (EGCG), (-)-gallocatechin gallate (GCG) and epigallocatechin‐3‐(3”‐O‐methyl) gallate (EGCg3”Me),13 modulated bacterial growth in the intestines.14 They inhibited the growth of harmful bacteria and helped beneficial bacteria to proliferate.
A second study evaluated the effect tea had on gut microbiota in light of the known anti-obesity properties.15 The results of this animal model suggested drinking tea substantially increases the diversity and structure of gut microbiota, which may have an impact on fat burning.
Researchers also demonstrated the polyphenols extracted from green tea, oolong tea and black tea could modulate intestinal flora and produce a greater number of short-chain fatty acids, contributing to a healthy gut microbiome.16
More Health Benefits Associated With Oolong Tea
Oolong tea is also rich in antioxidants — beneficial compounds that help reduce the effects of free radicals and reactive oxygen species.17 This plays a role in the development of various diseases, including diabetes, stroke, cancer and rheumatoid arthritis.
One study evaluated the effect of oolong tea on bone mineral density in 476 postmenopausal women.18 They were questioned about their lifestyle, types of tea they drink, demographic features and health status.
When researchers compared the tea drinkers against the non-tea drinkers, they found those drinking oolong tea had higher bone mineral density. It was significantly higher in those who drank one to five cups of tea per day but did not go up for those drinking more than five cups per day.
The antioxidants, caffeine and theanine found in oolong tea may also contribute to a lower risk of cognitive impairment and decline that researchers have found in community-living Chinese adults 55 years and older who consistently drank oolong or black tea.19
In a review of the literature, researchers identified an increase in insulin activity.20 This occurred with black, green and oolong teas with an increase in insulin activity of at least 15-fold in laboratory fat cell assays. Oolong tea also reduced plasma glucose and is believed to be an effective adjunctive treatment of Type 2 diabetes.
Oolong tea has been associated with a reduction in heart disease. In one study with 76,979 Japanese adults, those who drank 8 ounces or more of oolong tea each day significantly reduced their risk of cardiovascular disease mortality.21 In a separate study, those drinking one to two cups of green tea or oolong tea each day significantly reduced their risk of stroke.22
EGCG Helps Improve Zinc Absorption
During flu season and the COVID-19 pandemic, it bears remembering that the EGCG found in green, black and oolong tea can help improve absorption of zinc. Zinc is an essential mineral and a cofactor for nearly 3,000 proteins in the body.23
In addition to this, it is crucial for healthy immune functioning. Zinc deficiency has been shown to impair your immune function24 as it modulates cell mediated immunity and acts as an anti-inflammatory agent and antioxidant.25
Although there’s no cure for viral infections, your body uses a process to fight viruses that includes zinc. It has also demonstrated the ability to reduce the length of a cold by an average of 33%.26
One effective treatment for the early symptoms of COVID-19 has been a combination of hydroxychloroquine and zinc. Hydroxychloroquine is routinely used in the treatment of rheumatoid arthritis, lupus and other autoimmune diseases.27
The hydroxychloroquine acts as an ionophore, driving zinc into the cells where it can impair the replication of the SARS-CoV-2 RNA virus.28 Beyond immune health, zinc has an impact on wound healing, age-related macular degeneration, sense of smell and taste29 and blood sugar balance.30
EGCG is a major polyphenol component found in tea and has demonstrated the ability to act as a zinc ionophore, transporting zinc across the cell membrane.31 A study published in the Journal of Agricultural and Food Chemistry used a lab model to demonstrate EGCG and quercetin could rapidly increase levels of zinc in cells in the laboratory.32
They hypothesized that the ionophore activity of the dietary polyphenols tested may play a significant role in raising the levels of intracellular zinc and thus may be responsible for many of the biological actions attributed to the polyphenols.
Get the Most From Your Tea
While drinking oolong tea is healthy, using tea bags adds a level of toxins you don’t want. Tea bags may be more convenient, but many are made with heat resistant polypropylene that prevents the bag from breaking apart in hot water and releases minute pieces of plastic in each drink.33
Paper tea bags are treated with epichlorohydrin, which is a chemical that prevents tears and has been found to be a probable human carcinogen.34 Instead, seek out loose tea leaves and store them in an airtight container kept in a dry, dark cabinet away from direct sunlight and heat.
Since the processing techniques used affect the ideal brewing temperature, look for the directions on the package of tea you buy. However, here are some general tips to consider:35
- Use fresh, pure filtered water. Do not use distilled water as it will give your tea a flat flavor.
- In general, the tea should be steeped between 180 degrees and 200 degrees Fahrenheit for one to three minutes.
- Oolong teas can be used multiple times. With each cup the leaves open a little more, which releases more flavor. You may be able to get up to five uses out of a high-quality tea.
- Oolong tea tastes best after steeping for a short time, so it’s a good idea to taste it after the recommended time before deciding to steep it longer.
- Cover the tea while it steeps to keep all the heat in the vessel and try drinking it without any additives, such as milk or sugar, to improve the health benefits and appreciate the handcrafted flavor of the tea.