Help Cleanse Your Innards with Green Tea

Green Tea Boosts
Cancer Defense

It increases the activity of a major class of
detoxification enzymes in healthy people who may be deficient
By Will Block

ou put good, nutritious food and nutritional supplements into your body. And all those nutrients find their way into your cells, where they participate in myriad metabolic processes that will keep you healthy and happy, not to mention alive, for a long, long time. It’s all a marvel of clean, safe, efficient biochemistry, right?

Well, yes and no. The system does work very well, by and large. But if truth be told, your innards are in a constant state of biochemical turmoil owing to all the toxic byproducts of your metabolism. Like the pollutants that inevitably arise from industrial processes, the toxins resulting from metabolic processes must be disposed of somehow, lest they kill you—which they would, within an hour or so, if you didn’t have an efficient system for internal detoxification.

Will the Real Detox System Please Stand Up?

Much money is made by people with little or no scientific knowledge who tout a variety of “detoxification” and “cleansing” procedures involving questionable dietary regimens, black-box electrical treatments, colonic irrigations, saunas, etc. These procedures, which are usually promoted in pseudoscientific terms, have little or no proven value, and in some cases, they can be harmful rather than helpful. Caveat emptor.

A more rational, not to mention more cost-effective, approach is to learn how your body’s built-in detoxification system does an efficient job, 24/7—primarily via the liver, kidneys, and lower gastrointestinal tract—of keeping your innards “cleansed.” Then, armed with such knowledge, you can, perhaps, give the system a helpful boost through the use of nutritional supplements whose actions are elucidated by real scientists on the basis of actual scientific research. What a concept!

In this article, we’ll see how green tea can enhance your body’s ability to rid itself of unwanted chemical compounds. Let’s start with an overview of how your detox system works.

Why We Need Antioxidants

Our metabolism—the sum total of all the biochemical processes in our cells—produces the chemical energy needed to sustain life as well as all the compounds of which our bodies are composed. It also, however, produces waste products and torrents of harmful reactive oxygen species (ROS), including the notorious free radicals.

The paradox of ROS is that we couldn’t live without them, because some of them play vital roles in cellular function. Others do not, however, and we can’t live with them—we must eliminate them as quickly as possible. For that, we need endogenous (home-grown) antioxidants, with whatever extra help we can get via antioxidant supplements. These vital compounds neutralize ROS through either nonenzymatic chemical reactions or enzyme-catalyzed reactions. The most important of all antioxidants is glutathione, a compound produced in the cells of virtually all living things. (The locus of glutathione’s biological actions is a single sulfur atom in its molecular structure.)

Why We Need Detoxicants

In addition, our bodies are constantly exposed to xenobiotics—biologically active compounds that are foreign to us, such as industrial and agricultural pollutants, pesticides, food additives, and natural poisons; among the most pernicious xenobiotics are carcinogens. Our cells are programmed to get rid of such enemies. For that, they need detoxicants, which consist of several large families of enzymes whose role is to catalyze chemical reactions that neutralize the substances in question. (It’s annoying to realize that our bodies are ingrates, in that they also regard most medicines and some supplements as xenobiotics, so they try to get rid of those too, even while the medications are trying to do us good; this is a chronic problem in therapeutics.)

Our detoxification enzymes attack not just xenobiotics but also some endogenous substances that need to be removed, such as peroxidized lipids. In either case, the action occurs mostly in the liver, in two well-defined phases. In phase I, certain enzymes catalyze the oxidation, reduction, or hydrolysis (depending on the molecular characteristics involved) of the toxic compounds. This converts them into metabolites that can be further attacked (if the liver wishes) in phase II.*

*Because compounds that enter the bloodstream from the intestines go immediately to the liver (via the portal vein), the liver gets first crack at them and metabolizes most of them before they ever reach the general circulation—which they then do (if at all) mainly as metabolites rather than as the original compounds. This “first-pass metabolism” by detoxification (and other) enzymes in the liver accounts for many of the differences—often major ones—between the results of laboratory studies on various nutrients and those of clinical trials with the same nutrients. (For example, many compounds that exhibit antioxidant activity in cell cultures do not do so in living organisms, probably because they never even make it into the circulation.) In terms of assessing actual value, only the clinical results matter.

Glutathione Is Central to Antioxidant and Detoxification Activity

Two depictions of the glutathione molecule. The yellow ball is the sulfur atom.
In phase II, other enzymes catalyze the conjugation of the metabolites, i.e., their chemical linkage to some other molecule. Here that molecule is a naturally occurring one that typically enhances the metabolites’ solubility in the aqueous environment of the cells and facilitates their excretion via the urine, feces, sweat, or breath. In a sense, the compound to which the metabolites are conjugated acts as a molecular “usher” to escort them out one of those “doors.” (Sometimes there is a phase III process that further metabolizes the unwanted compound before it’s excreted.)

One of the families of phase II detoxification enzymes, playing a pivotal role in cancer prevention, is called glutathione S-transferase. Hello! There’s that word glutathione again. This is no coincidence. Not only is glutathione the body’s most important antioxidant, but it’s also the most important conjugating compound for xenobiotic metabolites. In the metabolites, atoms with a certain type of electronic structure are susceptible to attack by the sulfur (S) atom in glutathione. Once the chemical bond is formed (courtesy of glutathione S-transferase), the enemy is on its way to oblivion, as described above.

It’s worth noting that, in its role as an antioxidant, glutathione acts both independently and as a cofactor (a molecular collaborator) for the powerful antioxidant enzyme glutathione peroxidase, which would not be an antioxidant enzyme without the glutathione.

All of which must make you wonder why glutathione cannot be used successfully as a supplement. It’s because glutathione is a tripeptide (three linked amino acids) and is broken down in the digestive tract. It must therefore be synthesized in our cells from amino acids that are readily available there. Cellular glutathione levels are maintained, in part, by the action of the versatile and potent antioxidant alpha-lipoic acid (ALA), and some scientists believe that that is ALA’s single most important biological function.

Cancer Prevention Depends on Robust Detoxification

The integrity of our built-in detox system determines, to a large degree, our susceptibility to cancer. If this system becomes less efficient, whether through diminished levels of the enzymes or through their diminished biological activity, as we grow older, our risk for cancer will increase. Can that situation be remedied? Researchers at the University of Arizona and the National Cancer Institute think perhaps it can be.

In a 4-week study involving 42 healthy men and women aged 18 or over (the authors provided no data regarding their age distribution), the subjects were given a commercial green tea extract that was standardized to provide 800 mg daily of EGCG (epigallocatechin gallate), the polyphenol to which most of green tea’s health benefits, including anticancer activity, are attributed.1 The subjects took the capsules on an empty stomach (at least 1 hour before breakfast), because that maximizes the absorption of the polyphenols.

Why choose green tea? Because green tea was known from prior laboratory and animal studies to be an inducer of detoxification enzymes, including glutathione S-transferase (GST). Before the trial, the researchers measured the overall biological activity of the subjects’ GST, as well as their levels of the dominant type of GST (GST-π) in lymphocytes, which are white blood cells of the immune system. They then divided the subjects into three same-size groups called tertiles, representing the lowest, middle, and highest values of the baseline GST activity and level.

EGCG May Prevent Pancreatic Cancer

As cancers go, pancreatic cancer is among the worst. It tends to be silent and is thus not usually diagnosed until its late stages, when the prospects for recovery are very poor. It’s extremely resistant to chemotherapy and radiation therapy. Surgery is the only potential cure, but only 20% of patients are eligible for it; furthermore, the operation is complex and difficult and has a poor record of success. For all practical purposes, pancreatic cancer is a death sentence.

All the more reason, then, to try to prevent it by any means possible, as pointed out recently by a team of researchers at the University of Texas, who stated,1

A polyphenolic constituent, (–)-epigallocatechin-3-gallate (EGCG), is the major and most effective chemopreventive agent in green tea. EGCG has been shown to exert a growth-suppressive effect on human pancreatic cancer cells in vitro. It induces cell-cycle arrest and apoptosis in pancreatic cancer cells and thus holds great promise for development as a chemopreventive agent.

Apoptosis (pronounced ap·oh·TOE·sis) is the natural process of programmed cell death, or cell suicide, which occurs in order to make way for fresh new cells as existing ones become damaged or too old to function well. Many factors influence apoptosis, either inducing it or suppressing it, with results that are desirable or not, depending on which cells are targeted. Just as we want to prevent apoptosis in healthy cells, we want to induce it in cancer cells, especially those of pancreatic cancer in its earliest stages.

The Texas authors examined numerous molecular mechanisms, including the induction of apoptosis, by which EGCG may prevent pancreatic cancer. The details of their work are far too technical to describe here, but we can quote their summary statement:

In conclusion, we have shown a potential of EGCG as a chemopreventive agent for pancreatic cancer. EGCG induces apoptosis through multiple mechanisms . . . The ability of EGCG to inhibit growth and induce apoptosis in pancreatic cancer cells suggest [sic] that EGCG can be used in the management of pancreatic cancer prevention.


  1. Shankar S, Suthakar G, Srivastava RK. Epigallocatechin-3-gallate inhibits cell cycle and induces apoptosis in pancreatic cancer. Frontiers Biosci 2007;12:5039-51.

Green Tea Strongly Induced Detoxification Enzymes in Subjects with Low Levels—But How Old Were They?

Ribbon diagram of one-half of a glutathione S-transferase molecule. The other half can be similar or identical. Each contains ~220 amino acids.
Green tea had a dramatic but selective effect. After the 4-week treatment, the GST activity and GST-π level for the lowest tertile of baseline values had improved by 82% and 83%, respectively, indicating a major improvement in phase II detoxification function in that group. In the middle tertile, there was an appreciable but non-statistically significant improvement, and in the highest tertile, there was an appreciable decline. The authors suggested that this decline could be based on statistical anomalies in the data rather than on biological effects, and they pointed out that the overall (total-group) trend was toward improvement, not decline: it was +14% for GST activity and +17% for GST-π level.

It would have been of great interest to see whether the subjects’ baseline GST activity/level values—and hence their response to the green tea polyphenols—correlated with their age. The authors, however, reported no such analysis—an astounding oversight!

In any case, they concluded by saying, “. . . green tea polyphenol intervention may enhance the detoxification of carcinogens in individuals with low baseline detoxification capacity,” and they stated that a loss of GST-π activity has been associated with the development of cancer, citing prostate cancer as one that is characterized by an early and near-universal loss. Restoration of GST-π activity has been proposed as a rational measure for preventing prostate cancer (and, presumably, other cancers as well).

Forget about Ignorance—Take Action!

It’s most unlikely that you know what your baseline GST activity is. So how do you know whether or not green tea would help boost your detox capacity? You don’t. But it might—and considering the long list of well documented health benefits of green tea, it will almost certainly boost various aspects of your health, even if you don’t know what they are. So don’t worry about what you don’t know, and take action on what you do know: make green tea a permanent part of your nutritional regimen.


  1. Chow HHS, Hakim IA, Vining DR, Crowell JA, Tome ME, Ranger-Moore J, Cordova CA, Mikhael DM, Briehl MM, Alberts DS. Modulation of human glutathione S-transferases by Polyphenon E intervention. Cancer Epidemiol Biomarkers Prev 2007;16(8):1662-6. This paper must technically be regarded as an advertisement, because the cost of its publication was defrayed in part by the payment of page charges.

Will Block is the publisher and editorial director of Life Enhancement magazine.

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