Does Green Tea Prevent Cardiovascular Disease?
By William FaloonJanuary 2007
By William Faloon
On May 9, 2006, the FDA stated that there was no credible evidence to support the claim that green tea reduces cardiovascular disease risk factors.1
The FDA’s 21-page letter of denial was in response to a petition filed by a maker of green tea bags that sought to state a cardiovascular risk-reduction health claim on the label of its product.
Although the FDA identified dozens of published scientific studies suggesting that green tea might reduce heart attack and stroke risk, the agency decided that none of these studies met its criteria for allowing a health claim on the labels of green tea products.
On September 13, 2006, the Journal of the American Medical Association published a study that tracked the green tea consumption of 40,530 adults over an 11-year period. The study found that those who drank five or more cups of green tea a day cut their overall death rate by 16% compared to those who drank less than one cup of green tea a day.2
The most striking finding from this study was the reduction in cardiovascular death in those who consumed the most green tea. Women who drank five or more cups of green tea daily had a 31% reduced risk of dying from cardiovascular disease, whereas men who drank five or more cups had a 22% reduced risk of dying from cardiovascular disease.2
Stroke was the type of cardiovascular mortality against which green tea was shown to be most effective. Women who drank five or more cups of green teas had a 42% lower risk of stroke compared to those who drank less than one cup a day.2
Why the FDA Disagrees with Study Findings
The FDA’s criteria for allowing a health claim on the label of a food or dietary supplement is quite archaic. For example, the FDA does not recognize low-density lipoprotein (LDL) oxidation as a validated cardiovascular disease risk factor. Therefore, scientific studies in humans showing that green tea extract inhibits LDL oxidation are excluded from the FDA’s analysis of green tea’s efficacy.
The FDA’s antiquated position flies in the face of voluminous data showing that oxidized LDL severely damages the arterial wall and is a major contributor to atherosclerosis-induced heart attack and stroke.3-22
When choosing which studies of green tea to evaluate, the FDA excluded those that did not show significant reductions in total cholesterol, LDL, or blood pressure. According to the FDA’s logic, if green tea does not lower cholesterol, LDL, or blood pressure, then a claim cannot be made on a green tea label that it reduces cardiovascular disease risk factors. The FDA did acknowledge studies in which people who consumed 10 cups of green tea a day showed a significant decrease in total cholesterol and LDL.
Completely overlooked by the FDA analysis are published studies showing that green tea protects against heart attack and stroke via mechanisms (such as inhibiting abnormal platelet aggregation)23-32 that are different than the rudimentary measurements to which the FDA limited its green tea evaluation.
The FDA also made it clear that all in vivo animal studies are excluded from its analysis because these studies cannot mimic normal human physiological response to green tea ingestion. The FDA then found a reason to invalidate every human study that had ever shown a cardiovascular benefit in those who consumed green tea.
The FDA’s conclusion was that no credible evidence existed to support a cardiovascular risk-reduction claim on the label of green tea products.1 The recent study published by the American Medical Association, which included more study subjects and lasted far longer than any other previous study, did show a cardiovascular benefit to drinking greater amounts of green tea. Who then should consumers believe?2
Misconceptions About Green Tea Beverages
When green tea is consumed as a beverage, relatively little of its active polyphenols are absorbed into the bloodstream. This helps explain some inconsistent findings about how effective green tea may be in preventing common diseases.
The study published by the American Medical Association showed that daily ingestion of five or more cups of green tea reduced cardiovascular mortality and overall death rates. It also showed that those who drank two to four cups of green tea a day had less disease than those who drank less than one cup a day. This particular study failed to show a cancer risk reduction.2
The findings from another large human study, however, did show a 41% reduction in cancer incidence in those who consumed over 10 cups of green tea a day compared to those who consumed less than 3 cups a day. This same study showed a 28% reduction in cardiovascular disease incidence in those consuming 10 cups of green tea compared to those drinking less than 3 cups.33
Even the FDA’s unfavorable report on green tea pointed to studies showing that daily intake of 10 cups of green tea lowered total cholesterol and LDL.34
It would appear from these studies that optimal benefits from green tea occur when one drinks 10 or more cups a day. The problem is that few people are ever going to ingest 10 or more cups of green tea every single day. The good news is that they don’t have to.
Green Tea Extracts vs. Green Tea Beverages
Mainstream doctors often advocate obtaining nutrients from foods rather than supplements. A problem with certain nutrients, however, is that they are bound so tightly to food that less-than-optimal amounts of the active constituents are absorbed into the bloodstream.
Examples of nutrients that are better absorbed from supplements than from food include vitamin K, folic acid, and chlorophyll.35-37 Lycopene, on the other hand, may be better absorbed from cooked tomato products38 than from supplements.
In a recent study published in the American Journal of Clinical Nutrition, scientists sought to determine whether the active ingredients in green tea were better absorbed from green tea extract capsules or by drinking green tea. Thirty healthy test subjects were recruited and given either a specially prepared green tea beverage standardized for green tea’s most active constituents (such as EGCG and ECG) or equally standardized green tea extract capsules.39
The results showed that subjects who received the green tea extract caps had a 60% greater increase in EGCG (epigallocatechin gallate) and a 90% greater increase in ECG (epicatechin gallate) compared to those who drank the identical amounts of these green tea constituents in standardized beverage form. The antioxidant effects in those who swallowed the green tea caps were also greater than in the green tea drinkers.39
The scientists concluded that when administered in the form of a green tea supplement, the active constituents (polyphenols) showed enhanced bioavailability compared to when identical amounts of polyphenols were provided in a green tea beverage.39
One reason for conducting this study were previous findings that green tea polyphenols might be effective in preventing and treating cancer. By documenting that green tea extract supplements are superior to drinking green tea beverages, scientists now have a solid basis to test green tea extract capsules in human clinical studies.
Not All Green Tea Beverages Are the Same
The amount of polyphenols contained in green tea beverages varies considerably, depending on where the tea is harvested and how it is processed. One study examined 19 commercial brands of green tea and found significant variation in the content of the polyphenols EGCG and ECG. The scientists who conducted this study recommended that the labels of green tea bags state the amount of the polyphenols (EGCG and ECG) contained in each cup so that consumers know how many milligrams of these active ingredients they are consuming each day.40
Did the FDA Actually Get It Right This Time?
The FDA’s denial of a cardiovascular health claim was in response to a petition filed by a maker of green tea bags that sought to state that daily consumption of about one cup of green tea would reduce cardiovascular risk factors. The amount of polyphenols in this particular brand of green tea was 125 mg per cup.
Based on our analysis of the published scientific literature, it takes more than 125 mg a day of polyphenols to reduce cardiovascular risks. Although the FDA never mentioned this in its 21-page letter of denial, it would appear the FDA made the right scientific decision in disallowing this particular health claim on the label of green tea bags.
The good news for consumers is that green tea extract prices continue to plummet. This enables virtually everyone to ingest just two green tea extract capsules a day and obtain the amount of polyphenols (about 1250 mg) contained in 10 cups of green tea.
For longer life,
1. Qualified Health Claim Petition—Green Tea and Reduced Risk of Cardiovascular Disease (Docket No. 2005Q-0297) Letter of Denial.
2. Kuriyama S, Shimazu T, Ohmori K, et al. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA. 2006 Sep 13;296(10):1255-65.
3. Zhou ZX, Qiang H, Ma AQ, Chen H, Zhou P. Measurement peripheral blood index related to inflammation and ox-LDL, ox-LDLAb in patients with coronary heart disease and its clinical significance. Zhong Nan Da Xue Xue Bao Yi Xue Ban. 2006 Apr;31(2):258-62.
4. Naruko T, Ueda M, Ehara S, et al. Persistent high levels of plasma oxidized low-density lipoprotein after acute myocardial infarction predict stent restenosis. Arterioscler Thromb Vasc Biol. 2006 Apr;26(4):877-83.
5. Johnston N, Jernberg T, Lagerqvist B, Siegbahn A, Wallentin L. Oxidized low-density lipoprotein as a predictor of outcome in patients with unstable coronary artery disease. Int J Cardiol. 2005 Dec 7.
6. Shimada K, Mokuno H, Matsunaga E, et al. Circulating oxidized low-density lipoprotein is an independent predictor for cardiac event in patients with coronary artery disease. Atherosclerosis. 2004 Jun;174(2):343-7.
7. Holvoet P, Kritchevsky SB, Tracy RP, et al. The metabolic syndrome, circulating oxidized LDL, and risk of myocardial infarction in well-functioning elderly people in the health, aging, and body composition cohort. Diabetes. 2004 Apr;53(4):1068-73.
8. Doo YC, Han SJ, Lee JH, et al. Associations among oxidized low-density lipoprotein antibody, C-reactive protein, interleukin-6, and circulating cell adhesion molecules in patients with unstable angina pectoris. Am J Cardiol. 2004 Mar 1;93(5):554-8.
9. Nordin FG, Hedblad B, Berglund G, Nilsson J. Plasma oxidized LDL: a predictor for acute myocardial infarction? J Intern Med. 2003 Apr;253(4):425-9.
10. Tatsuguchi M, Furutani M, Hinagata J, et al. Oxidized LDL receptor gene (OLR1) is associated with the risk of myocardial infarction. Biochem Biophys Res Commun. 2003 Mar 28;303(1):247-50.
11. Tsai WC, Li YH, Chao TH, Chen JH. Relation between antibody against oxidized low-density lipoprotein and extent of coronary atherosclerosis. J Formos Med Assoc. 2002 Oct;101(10):681-4.
12. Wang TC, Hsu CC, Chin YP, Lin YL. The autoantibody expression against different source of oxidized low density lipoprotein in patients with acute myocardial infarction. Thromb Res. 2002 Aug 15;107(3-4):175-9.
13. Kelishadi R, Nadery GA, Asgary S. Oxidized LDL metabolites with high family risk for premature cardiovascular disease. Indian J Pediatr. 2002 Sep;69(9):755-9.
14. Dotevall A, Hulthe J, Rosengren A, Wiklund O, Wilhelmsen L. Autoantibodies against oxidized low-density lipoprotein and C-reactive protein are associated with diabetes and myocardial infarction in women. Clin Sci (Lond). 2001 Nov;101(5):523-31.
15. Ehara S, Ueda M, Naruko T, et al. Elevated levels of oxidized low density lipoprotein show a positive relationship with the severity of acute coronary syndromes. Circulation. 2001 Apr 17;103(15):1955-60.
16. Mustafa A, Nityanand S, Berglund L, Lithell H, Lefvert AK. Circulating immune complexes in 50-year-old men as a strong and independent risk factor for myocardial infarction. Circulation. 2000 Nov 21;102(21):2576-81.
17. Vaarala O. Antiphospholipid antibodies and myocardial infarction. Lupus. 1998;7 Suppl 2S132-4.
18. Holvoet P, Vanhaecke J, Janssens S, Van de WF, Collen D. Oxidized LDL and malondialdehyde-modified LDL in patients with acute coronary syndromes and stable coronary artery disease. Circulation. 1998 Oct 13;98(15):1487-94.
19. Ryan M, Owens D, Kilbride B, et al. Antibodies to oxidized lipoproteins and their relationship to myocardial infarction. QJM. 1998 Jun;91(6):411-5.
20. Wu R, Nityanand S, Berglund L, et al. Antibodies against cardiolipin and oxidatively modified LDL in 50-year-old men predict myocardial infarction. Arterioscler Thromb Vasc Biol. 1997 Nov;17(11):3159-63.
21. Schumacher M, Eber B, Tatzber F, et al. Transient reduction of autoantibodies against oxidized LDL in patients with acute myocardial infarction. Free Radic Biol Med. 1995 Jun;18(6):1087-91.
22. Vaarala O, Manttari M, Manninen V, et al. Anti-cardiolipin antibodies and risk of myocardial infarction in a prospective cohort of middle-aged men. Circulation. 1995 Jan 1;91(1):23-7.
23. Hernandez Figueroa TT, Rodriguez-Rodriguez E, Sanchez-Muniz FJ. The green tea, a good choice for cardiovascular disease prevention? Arch Latinoam Nutr. 2004 Dec;54(4):380-94.
24. Neuhaus T, Voit S, Lill G, et al. Platelet aggregation induced by the C-terminal peptide of thrombospondin-1 (4N1-1) is inhibited by epigallocatechin gallate but not by prostaglandin E1. Platelets. 2004 Nov;15(7):455-7.
25. Son DJ, Cho MR, Jin YR, et al. Antiplatelet effect of green tea catechins: a possible mechanism through arachidonic acid pathway. Prostaglandins Leukot Essent Fatty Acids. 2004 Jul;71(1):25-31.
26. Lill G, Voit S, Schror K, Weber AA. Complex effects of different green tea catechins on human platelets. FEBS Lett. 2003 Jul 10;546(2-3):265-70.
27. Deana R, Turetta L, Donella-Deana A, et al. Green tea epigallocatechin-3-gallate inhibits platelet signalling pathways triggered by both proteolytic and non-proteolytic agonists. Thromb Haemost. 2003 May;89(5):866-74.
28. Kang WS, Chung KH, Chung JH, et al. Antiplatelet activity of green tea catechins is mediated by inhibition of cytoplasmic calcium increase. J Cardiovasc Pharmacol. 2001 Dec;38(6):875-84.
29. de Maat MP. Effects of diet, drugs, and genes on plasma fibrinogen levels. Ann NY Acad Sci. 2001;936:509-21.
30. Kang WS, Lim IH, Yuk DY, et al. Antithrombotic activities of green tea catechins and (-)-epigallocatechin gallate. Thromb Res. 1999 Nov 1;96(3):229-37.
31. Yang JA, Choi JH, Rhee SJ. Effects of green tea catechin on phospholipase A2 activity and antithrombus in streptozotocin diabetic rats. J Nutr Sci Vitaminol (Tokyo). 1999 Jun;45(3):337-46.
32. Sagesaka-Mitane Y, Miwa M, Okada S. Platelet aggregation inhibitors in hot water extract of green tea. Chem Pharm Bull (Tokyo). 1990 Mar;38(3):790-3.
33. Nakachi K, Matsuyama S, Miyake S, Suganuma M, Imai K. Preventive effects of drinking green tea on cancer and cardiovascular disease: epidemiological evidence for multiple targeting prevention. Biofactors. 2000;13(1-4):49-54.
34. Kono S, Shinchi K, Wakabayashi K, et al. Relation of green tea consumption to serum lipids and lipoproteins in Japanese men. J Epidemiol. 1996 Sep;6(3):128-33.
35. Garber AK, Binkley NC, Krueger DC, Suttie JW. Comparison of phylloquinone bioavailability from food sources or a supplement in human subjects. J Nutr. 1999 Jun;129(6):1201-3.
36. Berg MJ. The importance of folic acid. J Gend Specif Med. 1999 May-Jun;2(3):24-8.
37. Ferruzzi MG, Schwartz SJ. Thermal degradation of commercial grade sodium copper chlorophyllin. J Agric Food Chem. 2005 Sep 7;53(18):7098-102.
38. van het Hof KH, de Boer BC, Tijburg LB, et al. Carotenoid bioavailability in humans from tomatoes processed in different ways determined from the carotenoid response in the triglyceride-rich lipoprotein fraction of plasma after a single consumption and in plasma after four days of consumption. J Nutr. 2000 May;130(5):1189-96.
39. Henning SM, Niu Y, Lee NH, et al. Bioavailability and antioxidant activity of tea flavanols after consumption of green tea, black tea, or a green tea extract supplement. Am J Clin Nutr. 2004 Dec;80(6):1558-64.
40. Seeram NP, Henning SM, Niu Y, et al. Catechin and caffeine content of green tea dietary supplements and correlation with antioxidant capacity. J Agric Food Chem. 2006 Mar 8;54(5):1599-603.