Pu-Erh could help you lose weight" or "Detox/minimizing tea", dark tea or Pu-Erh has a growing reputation as a fat burner. However, few information and sources are given in the media. What is the secret of this emblematic Chinese tea?
Pu-Erh tea is a tea that is originally produced in China. Unlike other types of teas, the harvested tea leaves undergo a microbial post-fermentation (bacteria and fungi). This will give Pu-Erh unique flavors. (For more information on Pu-Erh, please refer to the blog post The Teapot Library). In China and especially in Canton, Pu-Erh is a medicinal drink to ease digestion. It is this property that researchers have tried to understand and verify in animals and then in humans.
Pu-Erh's hatred against lipids
A bad digestion can result in a diet too rich in lipids. Indeed, in too large quantities, lipids are poorly absorbed by the cells of the intestinal wall. This can damage the barrier formed by the cells and can cause cramps, diarrhea, etc.
Over the last decade, it has been proven that Pu-Erh extracts are able to limit the absorption of lipids by the cells. This capacity is very similar to the one studied for green tea (1). Pu-Erh has also been shown to cause fat oxidation and decrease the synthesis of new fats (2)
Contrary to the classical scientific approach, Pu-Erh is much less studied in vitro¸ i.e. on cell cultures. The first studies were performed in rats in 1986 (3). These first studies revealed that lipid levels decreased significantly when the rats' diet was supplemented with Pu-Erh. Overweight, obesity but also sedentary lifestyle induces fat accumulation in subcutaneous and visceral tissues. Visceral fat lipids can be released and accumulate along the blood vessel walls. This is a factor in the development of serious cardiovascular diseases such as stroke or atherosclerosis. Thus, researchers wanted to understand if Pu-Erh was able to reduce the weight and the presence of lipids in the blood to prevent these risks.
Pu-Erh, a slimming partner for rodents since 1986
Although the first studies in rodents began almost 35 years ago, it is in the last decade that studies in rodents have been accumulating. In three studies dating from 2019, obese mice and rats lost an average of 25% of their body weight after consuming Pu-Erh (for a 100kg individual, this represents 25kg lost). Even more surprisingly, in the study conducted by Huang's team (4), the body weight of obese mice fed a diet rich in fat and Pu-Erh returned to that of healthy mice. To understand why this weight loss occurs, the research teams are looking at the different lipids in the blood and the digestive system.
The good, the bad, the cholesterol
Cholesterol is a lipid that is essential in maintaining the cell membrane. In the blood, cholesterol is carried by special proteins called lipoproteins. We speak of HDL (high density lipoprotein or "good cholesterol") and LDL (low density lipoprotein or "bad cholesterol"). HDL is able to capture cholesterol from the blood and transport it to the liver for elimination. LDL binds the cholesterol to the cells of the blood vessels to stiffen and maintain their walls.
With too much LDL and not enough HDL, blood vessels will become rigid which increases the risk of blockage. In a 2019 study (5), mice were fed a high-fat diet. Those who consumed Pu-Erh in addition had their HDL levels increased and their LDL levels dropped. The balance between these two cholesterols could be improved by Pu-Erh.
The enemy of saturated fat
Health campaigns recommend limiting the consumption of saturated fatty acids (cream, butter, milk, oil, etc). These fats are part of the composition of LDL. A too high proportion of saturated fatty acids leads to a real vicious circle. The amount of cholesterol deposited in the vessels is increased and the fatty acids can accumulate in the nascent arterial plug (6). A recent study (4) revealed that blood and liver saturated fatty acid levels decreased when obese mice on a high-fat diet consumed Pu-Erh. Moreover, these levels returned to values close to those of mice without a particular diet.
When intestinal bacteria and Pu-Ehr join forces
Last year, Xia's team (7) investigated the weight loss in obese rats after Pu-Erh consumption. They showed that it could be linked to the modification of the intestinal microbiota.
This broth of intestinal bacteria sometimes called "good bacteria" is known for its metabolic role (degradation of undigested nutrients, produce energy, synthesize vitamins) and its role of barrier (physical and immune cell barrier). The imbalance of the microbiota leads to a poor functioning of the digestive system. The link between obesity and the gut microbiota is beginning to be established as it has been shown that specific lipids overrepresented in obese patients, LPS, disrupt the functioning of the microbiota (8). It has been shown that the population of Akkermansia muciniphila (one of the most abundant bacteria of the intestinal microbiota) was more represented with an activity reinforced by Pu-Erh extracts, in particular in the presence of raw Pu-Erh extracts (7). The actions of Pu-Erh on weight would be multiple and could be interesting coupled with probiotics.
Should we adopt the Pu-Erh diet in humans?
To date, there are 2 studies conducted in overweight or obese patients. The first study, conducted in 2014 (9), is based on 70 patients with metabolic disorders that promote overweight and obesity. One group consumed Pu-Ehr extract powder capsules 3 times daily for 3 months. These patients lost 1.3 kg on average, without any particular diet. On the other hand, there was no evidence of changes in blood cholesterol and fatty acid levels.
The second study, conducted in 2016 (10), was based on 59 overweight or obese patients with blood cholesterol levels above the cut-off value. One group of patients consumed Pu-Erh powder twice daily for 20 weeks, without any special diet. On average, patients lost 1kg, with an overall decrease in arm, leg and pelvic circumference. Cholesterol levels decreased within 4 weeks, the LDL:HDL ratio was improved, and blood lipid levels decreased for the first 8 weeks before returning to baseline.
Although these results may seem modest, these 2 studies are based on an unchanged, potentially high-fat diet (2016 study). In addition, the weight loss is probably not due to other factors. It would be interesting to carry out new studies by associating Pu-Erh to a balanced diet to see if Pu-Ehr would optimize weight loss. However, we have to be careful with these two studies because they are based on Pu-Erh powder. There are currently no studies comparing the effects of powdered and infused Pu-Ehr. The proportion of micronutrients in the powder versus the infused leaf has not been measured. Finally, the difference between raw and cooked Pu-Erh is almost never studied. The only studies published contradict each other on the antioxidant power of raw versus cooked.
A Pu-Erh cure can't do any harm, in moderation of course!