Pu-erh Tea Could Save Your Kidneys
Adding to its anti-fat, anti-cholesterol, and anti-cancer benefits …While invigorating your taste buds
The aroma of the tea is shockingly complex: piney, resinous and yet also marine, like a forested seashore. The first sip pulls away from the beach and into the woods: It’s vegetal, salty, woody and earthy. It leaves a mineral—almost metallic—finish that coats the back of the throat and lingers for several minutes. Ocean, forest, mountain, earth—this is Pu-erh tea, one of the most obsessed-over and sought-after teas in the world, and one of the few teas that can improve with age. … There’s a feeling in the body beyond the aftertaste of Pu-erh that is almost emotional. … Above all, Pu-erh is a texture.
— David Lee Hoffman, Importer and Collector of Fine Teas1
Wine lover that I am, the above quote could apply to the sensual experience of tasting an exceeding great Bordeaux (forest), Burgundy (earth), Mosel (mountain), or Loire (ocean) wine, but no one wine could even capture what Hoffman says about Pu-erh (pronounced poo·air). If such a wine existed, combining the most tantalizing sensualities of many great tasting experiences, it would certainly be proclaimed to be an extraordinary celestial liquid, figuratively out of this world. Whatever! Yet, as we continue to discover, Pu-erh tea is so much more than taste (which only the oldest, at the perfect stage of maturity, can provide). This legendary tea, when properly selected and independent of cost, can deliver more health benefits than the sages of its past ever imagined. Ocean, forest, mountain, earth—as we have explicated—are useful metaphors for Pu-erh’s health span!
Pu-erh’s Mountain Range of Health Benefits
In previous articles in Life Enhancement, we have reveled in the ability of Pu-erh(especially when combined with green tea) to reduce obesity. But when considering other known mechanisms and benefits of Pu-erh, it becomes clear that this remarkable tea goes far beyond promoting weight loss: it also promotes a wide variety of enhanced health paybacks, including antioxidant, anticancer, and cholesterol lowering effects, not to mention lower blood pressure and blood sugar, along with improved bacterial flora in the intestines. There is even the exciting possibility that Pu-erh’s mechanisms might contribute directly to life extension (as the tea improves with age, so could you), a mountain-top benefit if ever.
Weight Loss Pay Dirt with Pu-erh
Before we go on, however, it is useful to point out that to achieve weight loss with Pu-erh, it is necessary to adopt a low-glycemic index diet (LoGID). This is true because while fatty acid synthase (FAS), an enzyme that plays a central role in the conversion of dietary calories to stored body fat in mammals (including humans), can be inhibited by Pu-erh tea, a “regular” Western diet is loaded with digestible carbohydrates. And this results in large oversupply of malonyl-CoA, the substrate for FAS. Thus, without a LoGID, this oversupply—formed in the fat-synthesizing pathway from glucose—simply overpowers any potential inhibition of FAS. But more and more people are adopting LoGIDs, so the power of Pu-erh earthy pay dirt may more readily be theirs and yours.
An Ocean of Unexpected TreasureImagine, how exciting it would be to find a small treasure in a place where there was no expectation of finding it. Like finding a pearl in an oyster, something like that happened to researchers in China when they discovered, in 2003, that an unusual kind of tea called Pu-erh* contains tiny amounts of a biochemical treasure that can help keep our cholesterol levels down and, therefore, our health and longevity prospects up.
The “Pu-erl” they found was lovastatin, one of the most effective cholesterol-lowering agents there is. Together with other members of the statin family, lovastatin is among the most widely prescribed drugs on earth, but when presented from a natural source, its drug-like liabilities are buffered. Recently, using a sample of Pu-erh tea that came from the Yunnan province of southwestern China (the source of almost all Pu-erh), but that was not otherwise identified, Chinese researchers confirmed that lovastatin was the only statin present in the tea, and its concentration was 139 nanograms per gram (dry weight), which is admittedly not much.2
* For an overview of this remarkable tea, see “Pu-erh Tea—Exotic, Aged, and Anti-Fat” in the June 2007 issue.
But measured amounts of lovastatin in Pu-erh tea could also depend on many other factors. Another recent paper has shown that when the fermentation of Pu-erh is carried out with a higher level of Streptomyces cinereus strain Y11 than many tea factories in Yunnan use, the result is a significantly higher amount of lovastatin produced, along with a high level of polyphenols that can significantly scavenge the well-known DPPH radical.3 The higher microbe orchestrated fermentation yielded the highest amount of statin (1012 ng/g). This may make all the difference in the anti-fat properties of some Pu-erhs vs. others.
As a possible explanation of the other health properties of Pu-erh, recent studies have shown that theabrownin (TB) fractionated from Pu-erh tea has a significant blood lipid-lowering effect, reducing serum triglyceride, total cholesterol and low density lipoprotein (LDL), while increasing HDL in rats fed a high fat diet (though not in those on a normal diet). The authors hypothesized that these effects were a result of alterations by TB in key enzymes involved in lipid metabolism and/or on cholesterol breakdown and excretion.4 In a more recent paper by the same authors, enzymes produced by microorganisms were found to be the main cause of TB formation during the fermentation of Pu-erh tea.5
Seeing the Forest From the Trees
Pu-erh is a Tumor Suppressor
In a recent study, using water extracts of Pu-erh tea, researchers analyzed the tumor cell growth inhibition activities on several genetically engineered mouse tumor cell lines.6 They found that at a concentration that did not affect wild type mouse embryo fibroblasts growth, Pu-erh tea extracts could inhibit tumor cell growth.
The researchers also found that Pu-erh tea extracts down-regulated the expression of mutant p53 in tumor cells at the protein level as well as messenger RNA level. Curiously, while p53 (also known as protein 53 or tumor protein 53) is a tumor suppressor protein that in humans is encoded by the TP53 gene, p53 is crucial in multicellular organisms. There, it regulates the cell cycle and thus functions as a tumor suppressor that is involved in preventing cancer. However, a mutant p53 will no longer bind DNA in an effective way, and, consequently, another needed protein will not be available to act as the “stop signal” for cell division. Thus, mutant p53 can cause cells to divide uncontrollably, and form tumors.
The toxicity of chemotherapeutic drugs has become one of the dominant issues in chemotherapy. New developments in cancer fields have focused more and more on cancer prevention, early diagnosis, and personalized medicine. Accordingly, chemicals which target tumor specific molecules and selectively kill tumor cells have become one of the most popular topics in drug screening.
In the Pu-erh/p53 study using the wild type control and genetically engineered tumor cell lines as the screening system, the researchers could easily differentiate the toxicity of drug treatment to normal cells from the tumor cell growth inhibition activity. As well, the specific genetic background provided advantages in identifying the molecular target of the treatment.
Other Natural Compounds May Enhance Pu-Erh Antitumor Activity
The investigators also showed that Pu-erh tea has comparable tumor cell growth inhibition activity with black tea and green tea. However, several independent groups have shown that the fermentation process of Pu-erh tea could reduce its total catechins and related antioxidant activity. Thus, it is reasonable to speculate that the tumor cell growth inhibition activity of Pu-erh tea is due to other natural compounds and further studies are needed to clarify this.
To repeat, an important finding from the study is that Pu-erh selectively inhibits tumor cell growth at a concentration that does not affect wild type cells. Specifically, at the concentration used, Pu-erh’s selective inhibition of tumor cells would greatly reduce the non-specific cytotoxicity thus providing a way for cancer prevention or treatment that potentially helps avoid the current problem of cytotoxicity caused by most conventional chemotherapy drugs.
Furthermore, the current study reveals that Pu-erh down-regulates the expression of p53 mutant at both mRNA and protein levels. Consequently, Pu-erh tea might eliminate the growth advantage of tumor cells with mutant p53. It is widely known that at least 50% of human tumors have p53 mutation, and that mutant p53 proteins induce cancerous function, impact tumor progression, and contribute to metastasis. Targeting mutant p53 has become one important strategy in drug screening and personalized cancer treatment. Thus, due to its down-regulation of mutant p53, Pu-erh tea has a significant potential in cancer treatment with low side effects.
Pu-erh Down-Regulates Heat-Shock Protein in Tumors
The heat-shock proteins HSP70 and HSP90 have been targeted for cancer therapy due to their high expression level in tumor cells and their chaperon-like characteristics for other cancer causing proteins, e.g., mutant p53. Importantly, the researchers found that Pu-erh tea treatment could slightly down-regulate both HSP70 and HSP90 protein levels in tumor cells. Their data reveal the action of Pu-erh tea on tumor cells and suggest the possible mechanism for Pu-erh tea action, which explained its selectivity in inhibiting tumor cells without affecting wild type cells. Altogether, the data sheds light on the application of Pu-erh tea as an anti-tumor agent with low side effects.
The point to drive home is that the data showed that the same concentration of Pu-erh tea solution did not cause p53 stabilization or activation of its downstream pathways in the wild type cells. The analysis did not show any growth inhibition of wild type cells by Pu-erh tea treatment. These new findings reveal the action of Pu-erh tea on tumor cells and provide a possible mechanism for Pu-erh tea’s selectivity, targeting tumor cells without affecting wild type cells. This is good news in the fight against tumors of the breast, colon, stomach, hematopoietic and reticuloendothelial systems, liver and intrahepatic bile ducts, bronchus and lung, and brain.
A New Power of Pu-erh
The accumulation of advanced glycation end products (AGEs) has been implicated in the development of diabetic nephropathy (DN). You may not have known that DN is now considered to be the leading cause of endstage renal failure as well as a life-threatening complication of diabetes mellitus. Nearly 30% of diabetics suffer from DN, eventually undergoing renal dialysis or transplantation. The pathologic changes that accompany DN are persistent albuminuria, altered creatinine clearance, mesangial cell matrix expansion (specialized cells around blood vessels in the kidneys), glomerular basement membrane thickening, and glomerular sclerosis (see below).
These are the same changes observed in diabetic (db/db) mice, manifesting genetic obesity-induced type 2 diabetes. These mice also are prone to severe obesity, insulin resistance, hyperglycemia, and other diabetic complications. Subsequently in a new paper, researchers investigated the effects of Pu-erh tea on AGE accumulation associated with diabetic nephropathy.7
What is amazing is that Pu-erh
held its own in comparison to
Rosiglitazone, a drug that
has significant side effects,
including the possibility of an
increased risk of heart attacks, by
43% according to one study.
While Pu-erh did not affect blood glucose levels or insulin sensitivity, treatment for 8 weeks lessened increases in serum creatinine, urinary albumin, and mesangial matrix in diabetes-prone mice. Of significance, Pu-erh tea also prevented diabetes-induced AGE accumulation and led to reduction of AGE receptor expression in glomeruli, the network of capillaries in the basement membrane of the kidneys that filter blood impurities to form urine. Once this filtration process is severely impeded by the buildup of AGEs, the toxicities that remain can kill you. Among the scientist’s other findings is the probability that both the production and clearance of carbonyl compounds—the main precursor of AGE formation—were lessened by Pu-erh tea in vivo independent of glyoxalase I expression. The glyoxalase system is a set of enzymes that carry out the detoxification of methylglyoxal and the other reactive aldehydes. In vitro analysis demonstrated that Pu-erh tea could trap methylglyoxal in a dose-dependent manner, thereby defusing toxification. This study shows that Pu-erh tea may inhibit AGE formation by carbonyl trapping, and as a consequence may help prevent or arrest the progression of diabetic complications.
Pu-erh Stands Up to Antidiabetic Drug
Rosiglitazone, an antidiabetic drug in the thiazolidinedione class of drugs was used as an established drug, as a means of comparison. It works as an insulin sensitizer, by binding to the receptor proteins that regulate the expression of genes in fat cells, making the cells more responsive to insulin. What is amazing is that Pu-erh held its own in comparison to Rosiglitazone, a drug that has significant side effects, including the possibility of an increased risk of heart attacks, by 43% according to one study,8 leading to the FDA restricting access to the drug.9 On the other hand, Pu-erh not only has been found free of side effects, it appears to be safe at doses of 5,000 mg/kg/day in rats, the human equivalent of nearly 69 g/day for a 187 lb human. That’s a big safety margin.
After all of this, and along with the justified assumption that there will be more to come, we could say “Pu-erh to the people!” Returning to the metaphors: now you can see the forest from the trees, firmly implanted in the earth, and from the mountain on which it exists, the ocean below. Pu-erh is an important addition to your health program.
Advanced glycation end products
Fatty acid synthase, an enzyme that plays a central role in the conversion of dietary calories to stored body fat in mammals
the network of capillaries in the basement membrane of the kidneys that filter blood impurities to form urine
Low-glycemic index diet
Theobrownin, a component of Pu-erh found to lower bad lipids and increase the good one
- Wong DP. Bold & Beautiful. Imbibe Liquid Culture Jan/Feb 2009. http://www.imbibemagazine.com/Bold-Beautiful-Pu-erh-Teas.
- Yang DJ, Hwang LS. Study on the conversion of three natural statins from lactone forms to their corresponding hydroxy acid forms and their determination in Pu-Erh tea. J Chromatogr A 2006;1119:277-84.
- Jeng KC, Chen CS, Fang YP, Hou RC, Chen YS. Effect of microbial fermentation on content of statin, GABA, and polyphenols in Pu-Erh tea. J Agric Food Chem2007 Oct 17;55(21):8787-92.
- Gong J, Peng C, Chen T, Gao B, Zhou H. Effects of theabrownin from pu-erh tea on the metabolism of serum lipids in rats: mechanism of action. J Food Sci 2010 Aug 1;75(6):H182-9.
- Wang Q, Peng C, Gong J. Effects of enzymatic action on the formation of theabrownin during solid state fermentation of Pu-erh tea. J Sci Food Agric 2011 Oct;91(13):2412-8.
- Zhao L, Jia S, Tang W, Sheng J, Luo Y. Pu-erh tea inhibits tumor cell growth by down-regulating mutant p53. Int J Mol Sci 2011;12(11): 7581-93.
- Yan SJ, Wang L, Li Z, Zhu DN, Guo SC, Xin WF, Yang YF, Cong X, Ma T, Shen PP, Sheng J, Zhang WS. Inhibition of advanced glycation end product formation by pu-erh tea ameliorates progression of experimental diabetic nephropathy. J Agric Food Chem 2012 Apr 16. [Epub ahead of print]
- Nissen SE, Wolski K. Effect of rosiglitazone on the risk of myocardial infarction and death from cardiovascular causes. N Engl J Med 2007 Jun 14;356(24):2457-71. Epub 2007 May 21.
- Woodcock J, Sharfstein JM, Hamburg M. Regulatory action on rosiglitazone by the U.S. Food and Drug Administration. N Engl J Med 2010 Oct 14;363(16):1489-91. Epub 2010 Sep 23.