GREEN TEA AND LIVER TOXICITY
Posted on January 11 2014
Supplements are an essential part of training. If you want to be an elite athlete or professional bodybuilder, you need to use high-quality effectual supplements. The use of nutritional supplements in the United States has been on the rise for many years.
It is my hope that this is because of increased interest in health and longevity. Although the truth is likely that the rising costs of health care may be a stronger drive for preventative supplementation and self-medication. More people are interested in "natural" and "organic" products than ever. Thus, the herbal supplements made from various extracts have also become increasingly popular.
Herbal supplements are not regulated by the U.S. Food and Drug Administration (FDA) the same way as prescription and over-the-counter drugs. Herbal supplements can make it to the market much quicker without documented evidence of safety or efficacy. However, it is expected by the FDA that supplements demonstrate safety and perform according to their manufacturer's claims. It is the job of the FDA to recognize supplements that pose a risk to consumers and investigate the casual nature of the injuries. The Federal Trade Commission (FTC) holds the job of investigating and maintaining truth in advertising. Therefore, supplement companies must be careful not to make misleading claims. The FTC can take down your ads, and the FDA can recall your supplement.
There are a number of organizations like NSF International and the United States Pharmacopeia (USP) that evaluate the quality and safety of dietary supplements. These organizations can provide a valuable service by independently evaluating supplements. Otherwise, you have to go by a supplement company's reputation and experiment for yourself. Attention to this is critical in a time when rogue companies seem to pop up daily. All that being said, there are many high quality, effective herbal supplements on the market.
One of the Most Popular Herbal Extracts
Green tea extract (GTE) is one of the most popular herbal extracts on the market today, found in over 100 supplements.1 GTE contains polyphenolic substances called catechins that can be found in many plant extracts including the leaves of Camellia sinensis.2 Most of these extracted polyphenols are utilized in supplements for their antioxidant properties. Briefly, an antioxidant is a compound that scavenges "free radicals." These are very reactive molecules that set off chain reactions in tissues like cell membranes and DNA, and cause significant damage if left unchecked. These oxidation reactions are thought to lead to cancers, degenerative brain diseases and cardiovascular disease. You maintain healthy antioxidant levels via production by your healthy body (e.g., glutathione, enzymes, etc.) or consumption in your veggie-rich diet (e.g., polyphenols, vitamins C and E, etc.). However, it is often left out of discussion that polyphenols can also have "PRO"-oxidant properties. I will elaborate.
The green tea polyphenol "epigallocatechin-3-gallate" (EGCG) is the most studied of the antioxidant catechins. A cup of green tea has ~180 milligrams of EGCG with one-third less in decaffeinated teas. Most GTEs are standardized for their EGCG content. The beneficial effects of GTE have been proven in clinical and laboratory studies and are often attributed to EGCG. Of particular interest to bodybuilders is that GTE has been shown to improve fat burning.3 The potential mechanisms by which GTE improves fat loss involve inhibition of fat cell division, reduced fat absorption from food, increased sympathetic nervous system activity, increased energy expenditure (thermogenesis) and improved utilization of fat.4 Studies have shown that regular drinking of green tea over 10 years correlates with lower body fat percentage.5
So what's the catch? Whenever we discuss fat-loss supplements, we always have people who tend to take things to the extreme and live by the "more is better" philosophy. In previous articles, we have discussed how there's a "Goldilocks" (just right) level for taking antioxidants. Oxidative stress occurs during exercise. It is this stress that "shocks" the system into generating adaptations to that exercise.6 Those adaptations include improved mitochondrial energy production and efficiency. If the stress is too high, cell damage occurs. If it is too low, you get very little adaptive change. If you take too much of an antioxidant like EGCG, you can blunt your response to exercise. It is difficult to know how much is "just right" for you, so we have to rely on science to tell us what works for a group of subjects similar to you.
No Significant Health Threat
What science has shown over and over again is that reasonable consumption of GTE does not pose a significant threat to your health.7 Human studies have shown that doses of up to 1.6 grams of GTE are fairly well tolerated.1 It's been reported that the maximum dose is thought to be 9.9 grams per day- equivalent to 24 cups of green tea! The side effects of doses greater than 1 gram of GTE can include headaches, nausea and dizziness. Multiple studies have examined the effects of EGCG on exercise, cancer and many other conditions, without many adverse effects noted. However, since humans are diverse beings with diverse habits, occasionally we will see outliers. This is especially true when it comes to a supplement like GTE that is extraordinarily popular and used by millions. Unfortunately, a number of case reports have implicated GTE supplementation as a potential cause of liver failure.7
A similar situation can be seen with another compound that is used by millions, Tylenol. Tylenol, or acetaminophen, can cause liver failure with a single dose. I have seen this during my career. The antioxidant glutathione protects the liver from the oxidative damage that can occur with Tylenol toxicity. Case studies have demonstrated that the cellular damage that occurs with GTE toxicity looks quite similar to Tylenol toxicity. GTE seems to induce excessive free radical damage with destruction of mitochondrial membranes.8 One study tried to show that the antioxidant effects of GTE could blunt the toxic effects of high doses of Tylenol in mice.9 In this study, researchers gave mice the human equivalent of ~3 to 6 grams of GTE after the Tylenol, and showed that this worsened the toxicity. On the flip side, if they gave the GTE before the Tylenol it seemed to help. Further, a study in rats and mice dosing a human equivalent of ~3 grams per day demonstrated no adverse events at this dose.12
Pro-oxidant Effect and Toxicity Concerns
Why acetaminophen or GTE seems to affect a few individuals is unclear. Some individuals may have a genetic predisposition or hypersensitivity. It may be that these individuals were inherently low in antioxidants and in an overly inflammatory state to begin with.10 One thing is becoming clear in the scientific literature- EGCG can also act as a PRO-oxidant. It is believed that this pro-oxidant effect may be the way EGCG kills tumor cells.2 The EGCG component also seems to be the most damaging to liver and tumor cells when compared to the other catechins found in GTE.11 One study suggests that metals may be involved in the pro-oxidant effects, as copper-oxidized EGCG seemed to be more toxic to cancer cells.2 Perhaps your GTE shouldn't be taken with your mineral supplement?
There are a lot of variables that need to be considered when it comes to the potential toxicity of GTE. First, the absorption of GTE is remarkably increased when taken on an empty stomach. If you are taking GTE on an empty stomach, you should consider a lower dose. Second, the catechin content of GTEs can vary greatly. It is hard to know when you are getting too much, so stick to reliable manufacturers and use in moderation. Third, it is important to avoid taking GTE with other potentially liver-toxic compounds. Alcohol, Tylenol, usnic acid and other medications have liver-toxic effects; if you are unsure about something you are taking, consult your physician. Fourth, if you are taking any supplement and you start to experience fatigue, malaise, or abdominal pain, stop and see your physician for some labs. There are a number of supplements on the market tainted with liver-toxic steroids and compounds like usnic acid. Finally, remember the "Goldilocks" principle that you should avoid excessive antioxidants. Supplements should be just that, "supplements." They are to be supplemental to your balanced diet.