September 6, 2005
The Elixir of Life: Green Tea or Red Wine?
Green tea, steeped in an ancient civilization, conquered the West because of its supposed health effects. Wine, particularly red wine, is a relative newcomer to the health scene. Tea leaves and red grapes are said to line the path to a long and healthy life. The evidence, however, is not convincing.
Hot infusions of the leaves of Camillia sinensis have been used in China for "thousands of years," supposedly discovered by emperor Shen-Nung in 2737 B.C. He accidentally dropped a few leaves into boiling water, and the warm drink made him feel better. Tea drinkers outside Asia prefer black tea, made by roasting and fermenting the leaves. Tea contains caffeine, which stimulates the central nervous system. It is also a diuretic and a respiratory stimulant. That a warm cup of tea can "perk you up" has a firm physiological basis. This is also true for other caffeine-containing stimulants, like coffee or cocoa, but tea boasts that romantic history of an ancient emperor fumbling with tea leaves and hot water.Initially, green tea became important in human health because of the stimulating effect of caffeine; the emperor did not know about antioxidants. Today, antioxidants in tea, particularly green tea, are said to protect us from cancer. Why? Notwithstanding high rates of cigarette smoking, the teadrinking Chinese have one of the lowest lung cancer rates in the world.
But what about the other killer, heart disease? Green tea research makes no mention of our hearts at all. Well, it appears we just have to drink more. Red wine this time, another beverage rich in antioxidants. That is because of the French. They eat a rich diet with butter and creamy cheeses like Camembert and Brie, and according to a French diet writer, few or no vegetables (Montignac 1998). Yet the French enjoy the lowest rate of heart disease among Western countries. Apparently, this so-called French Paradox is explained by the French custom of drinking wine with their meals (Renaud and de Lorgeril 1992).
The wine antioxidants occur mostly in grape skin, so only red wine, which is fermented "on the skin," will do. However, the antioxidants in green tea are close chemical relatives of the antioxidants in red wine. So the real paradox is this: antioxidants in green tea specifically protect the Chinese from lung cancer while other, very closely related antioxidants in red wine specifically protect the French heart. Obviously we must drink both green tea and red wine. And, according to other nutrition authorities, we already need three glasses of milk and six glasses of water a day. This could give a whole new meaning to "being on a liquid diet." The question is, how solid is the evidence?
There is no question about the antioxidant properties of some green tea constituents like epigallocatechol gallate (EGCG). Like many other plant extracts, green tea inhibits growth of cancer cells in the lab and in some rodents, but studies on humans are quite inconclusive. In fact, a meta-analysis of some thirty studies mentions several reports that link green tea consumption with an increased incidence of some cancers (Bushman 1998).
On the other hand, the French Paradox has become a popular overlay on the picture of the much-studied Mediterranean diet, which is rich in antioxidant-containing vegetables, like cabbage and tomatoes, unsaturated fats like olive oil, and wine (Matalas et al. 2001). This diet is said to decrease the incidence of heart disease and promote longevity. The French Paradox made the benefits of red wine into nutritional doctrine. Resveratrol, the main antioxidant in red wine, may even protect against cancer (Jang et al. 1997), although it can also promote atherosclerosis (Wilson et al. 1996).
As is the case with the green tea literature, there is also disagreement on the wine story. Some reports mention increased antioxidant activity in blood serum after red wine consumption (Maxwell et al. 1994), while others suggest it is just the alcohol, independent of the type of beverage, that does the trick (Klatsky et al. 1997). So, the paradox remains. Surely if antioxidants protect the Chinese from lung cancer and the French from heart attacks, we would also expect the Chinese to have fewer heart attacks, and the French to have low lung cancer rates. And shouldn't both the Chinese and the French live longer than the rest of us?
Reading the Numbers in the Tea Leaves
Experts in tea, wine, and the Mediterranean diet often mention higher life expectancies and frequently make claims of exceptional longevities. These numbers can be measured and are available in several places. The United Nations publishes a vast amount of information on many aspects of human life. The forty-eighth issue of the United Nations Demographic Yearbook (1996) concentrated on mortality statistics.
Unfortunately, the life expectancy statistics are not very helpful. The Yearbooks table 4 gives us male and female life expectancy at birth. When we follow the example of some actuaries and average the male and female numbers to get a less complex picture of unisex data, we see that Mediterranean Greece and France don't particularly stand out from other industrialized countries. The tea-drinking Japanese are indeed at the top but the tea- drinking Chinese rank last.
Table 1. Unisex life expectancy at birth.
Of course, life expectancy at birth is readily confounded by infant mortality. However, if green tea and red wine are healthy, drinkers should live longer than non-drinkers. The Yearbook's table 7 contains the numbers of total populations and of the over-65 cohorts, by country. Converting these large, unwieldy numbers into percentages allows for a quick comparison of a few selected countries' cohorts older than age 65 (table 2, 1990s data). Although population fractions of older people can be confounded by birth rates, table 2 does show a trend, and it doesn't point the same way as the data on life expectancy.
Japan and France, with high life expectancies, rank below average in the over-65 age group, and Mediterranean Greece ranks below non- Mediterranean Sweden. In Canada and the U.S. the over-65 cohort is much lower. Maybe we eat too much, or perhaps we drive too fast. The Chinese are again at the bottom.
Since we are dealing, presumably, with long-term life styles, it matters little that the Yearbook's data are from the early 1990s. We find 2003 updates of these figures at the Population Reference Bureau (www.prb.org). And behold, despite worldwide pollution and poor eating habits, in little more than a decade nearly all life expectancies increased by a few years, and the over 65 cohort has grown in all countries. An anomaly in the more recent figures is a jump in the over-65 group in Japan and in Greece to 19 percent of their populations, which bumps Sweden from its top ranking. Whether these are true, one-decade improvements, or just anomalies in data collecting or reporting is unclear.
Table 2. The over-65 cohort as a percentage of total population.
Whatever the benefits of red wine and green tea, so far we see no convincing numbers that a longer life is one of them. However, there are further useful numbers. The Yearbook also shows rates of death by cause in its table 29. China is missing from this table, but there is another source of information for that country. Of course, rate of death due to a given disease is not the same as the incidence, the actual frequency of occurrence, of that disease. Relevant to the green tea issue, the mortality rate due to lung cancer in Japan, at 34.8 per 100,000, is higher than in Israel and Sweden, and marginally lower than in Finland and Norway.
A two-part report sheds light on the Chinese lung cancer issue. In industrialized countries, cigarette smoking in males increased strongly during the early twentieth century, stabilizing by the 1950s. Deaths directly attributable to tobacco began to rise well after mid-century, and reached a plateau in the 1990s. Thus, a delay of several decades separates an increase in smoking from the increase in smoking-related deaths. Early low smoking rates among Chinese males started to increase well after 1952, and only reached today's high level by 1996. Applying a similar delay, smoking- related deaths in China will reach significantly higher levels only around 2030. Chinese male mortality directly attributable to smoking, about 12 percent in 1990, is expected to rise to 33 percent by 2030 (Liu et al. 1998). Clearly, the idea that China and Japan have the lowest lung cancer rates in the industrial world because of their tea drinking habits is at odds with these readily available health statistics.
In the Yearbook's table 29 on mortality rates, causes of death are identified by several dozen internationally agreed-upon codes, like AM29 for "acute myocardial infarction," and AM30 for "other ischemic heart diseases." An analysis of these numbers shows that, indeed, mortality rates due to heart dis ease in France and Spain are the lowest in the Western world, and lower still in Japan. Greece ranks above nonMediterranean Belgium, but well below the Northern European countries. The Mediterranean and Japanese hearts seem okay, but their arteries are not. That same table 29 in the Yearbook shows that both France and Greece ra\nk among the highest in mortality rates due to circulatory disease.
And in the end, a comparison of all-cause mortality rates makes much of the red wine hype disappear among the many other, different causes from which people die. Curiously, France also has the third highest mortality rate due to liver disease, after Germany and Spain. Alcohol is a liver poison, and more than three drinks daily significantly increases cancer risks. Perhaps alcohol with every meal, be it French wine or German beer, is not such a good idea after all.
Some data seem to support claims that the Japanese have the highest average life span among industrialized countries, although these claims seem to be based on a comparison of life expectancies (Kobayashi 1992). Also, the Mediterranean countries do have lower total mortality rates than the Scandinavians, though these rates are lower still in Japan, Canada, and Australia. However, there are several other interesting observations that offer more plausible explanations than the tea and wine stories.
British researchers proposed a simple explanation for the French Paradox. Consumption of animal fat, a major dietary cause of heart disease, increased substantially in France between 1965 and 1988. Their study also shows a considerable time lag between long-term fat consumption and the onset of atherosclerosis. They explain the current low rate of heart disease in France by a simple time-lag phenomenon, and predict that this rate will rise in the coming decade (Law and Wald 1999). A similar increase in the consumption of animal fat took place in several other Mediterranean countries (Serra-Majem et al. 1995, Matalas et al. 2001). The story is not unlike that of the cigarette smoking Chinese. Clearly, the Mediterranean diet is changing. Again, proof is still some years away.
Spanish researchers also studied diet and heart disease in their country. They came up, surprise, with the Spanish Paradox (Serra- Majem et al. 1995). That report did not generate the same fuss as the French Paradox, maybe because the Spaniards lacked the glamour of the red wine. Their "paradoxical" results do show a decrease in heart disease mortality from the mid 1970s onward. However, during the two relevant decades, the Spanish dramatically increased their consumption of meat, fat, and dairy products. They also decreased their consumption of super-healthy olive oil and replaced it with cheaper seed oils. Also, the Spanish researchers could not use red wine to explain their paradox, because between 1975 and 1995 Spanish wine consumption decreased by nearly 50 percent. These observations contrast markedly with current popular view of the Mediterranean diet. Not surprisingly, that report concludes with the suggestion that diet, although important, is probably not as important as other factors operating in Spain, and elsewhere, such as improved medical resources, an aggressive antismoking campaign, and the increased use of aspirin as a preventive blood thinner.
Then there is the story about a gene on human chromosome 19, which codes for a protein called apolipoprotein E. When this apolipoprotein binds with cholesterol and fatty acids, it forms the high and low density lipoproteins (HDL and LDL) that control the transport of fats in our blood. Inherited variations in this gene lead to different forms of apolipoprotein E. A variant called E3 is better at handling fat transport than another variant called E4. If your parents gave you the E3 variant, you can handle dietary fat better, and your risk of cardiovascular disease is lower, than if you were born with the gene for E4. Very few diet writers mention this important influence of genetics (Matalas et al. 2001).
The gradient of the frequency distribution of these genetic variants across Europe almost look like the isobars on a weather map, with E3 more prevalent in southern Europe, around the Mediterranean, and E4 much more common in the North (Lucotte et al. 1997). When it comes to cardiovascular disease and fat metabolism, South Europeans have a genetic advantage. Yes, heart disease is less common in the Mediterranean area. Whether it is their diet or their genes, we don't know. Perhaps the Mediterraneans are just a few decades behind with destroying their healthy eating habits.
A similar effect, hidden in the genetic past of human evolution, may explain Japanese longevity. In a Japanese study we find that a mutation in mitochondrial DNA, which may be linked to longevity, is relatively rare in the global population, but occurs in almost half the population of Japan. Japanese longevity, if it is real, may have more to do with a genetic quirk than with diet (Tanakaetal. 1998).
So, while green tea is still hidden in the fog of uncertainty, it may be a good idea to hang on to Happy Hour. There are definite indications that a few drinks a day of any alcoholic beverage can reduce the risk of heart disease, although evidence that red wine is best remains elusive (German and Walzem 2000). And the Mediterranean diet, stripped of the hoopla of the French Paradox, does have distinct health benefits, both in terms of survival after cancer (De Lorgeril et al. 1998), and after a first heart attack (Matalas et al. 2001).
Clearly, there is little evidence for labeling green tea as an anti-cancer beverage. And what happens to our hearts may have more to do with our genes than with red wine. Still, maintaining good drinking habits seems a good idea.
Like many other plant extracts, green tea inhibits growth of cancer cells in the lab and in some rodents, but studies on humans are quiete inconclusive.
Bushman, J. L. 1998. Green tea and cancer in humans: A review of the literature. Nutrition and Cancer 31(3):151-159.
De Lorgeril, M., et al. 1998. Mediterranean dietary pattern in a randomized trial: prolonged survival and possible reduced cancer rate. Archives of Internal Medicine 158(11):1181-7.
German, J. B., and R. L. Walzem. 2000. The health benefits of wine. Annual Reviews of Nutrition 20:561-93.
Jang, M., et al. 1997. Cancer chemopreventive activity of resveratrol, a natural product derived from grapes. Science 275:218- 220.
Klatsky, A. L., et al. 1997. Red wine, white wine, liquor, beer, and risk for coronary artery disease hospitalization. American Journal of Cardiology 80(4):416-20.
Kobayashi, S. 1992. A scientific basis for the longevity of Japanese in relation to diet and nutrition. Nutrition Reviews 50(12):353-354.
Law, M., and N. WaId. 1999. Why heart disease mortality is low in France: the time lag explanation. British Medical Journal 318:471- 80.
Liu, B. Q., et al. 1998. Emerging tobacco hazards in China: Part 1. Retrospective proportional mortality study on one million deaths. British Medical Journal 317:1411-22. Part 2. Early mortality results from a prospective study. Ibid.: 1423-4.
Lucotte, G., et al. 1997. Pattern of gradient of apolipoprotein E allele 4 frequencies in Western Europe. Human Biology 69(2):253- 262.
Matalas, A. L., et al. Eds. 2001. The Mediterranean diet: constituents and health promotion, Boca Raton: CRC Press.
Maxwell, S., et al. 1994. Red wine and antioxidant activity in serum. Lancet 344:193-4.
Montignac, M., 1999. Eat Yourself Slim. Baltimore: Erica House, p.120.
Renaud, S. and M. de Lorgeril. 1992. Wine, alcohol, platelets, and the French paradox for coronary heart disease. The Lancet 339:1523-6.
Serra-Majem, L., et al. 1995. How could changes in diet explain changes in coronary heart disease mortality in Spain? The Spanish Paradox. American Journal of Clinical Nutrition 61 (SuppL): 1351S- 9S.
Tanaka, M., et al. 1998. Mitochondrial genotype associated with longevity. Lancet 351 (9097):185-6.
United Nations Demographic Yearbook, 48th Issue, 1996. Special issue on mortality statistics.
Wilson, T., et al.1996. Resveratrol promotes atherosclerosis in hypercholesterolemic rabbits. Life Sciences 59(1): 15-21.
William H. Baarschers is a professor emeritus of chemistry at Lakehead University in Thunder Bay, Ontario. His research interests have included the chemistry of medicinal plants, synthetic chemistry, environmental science, and industrial toxicology. He is currently an advisor to the university's Resource Centre for Occupational Health and Safety. He is the author of Eco-Facts and Eco-Fiction: Understanding the Environmental Debate (Routledge, 1996).
Copyright The Committee for the Scientific Investigation of Claims of the Paranormal (SCICOP) Sep/Oct 2005