Drinking green tea associated with less heart attack

Green tea is in the headlines again. Over the past few years, green tea has been in the spotlight for its purported weight loss, cholesterol-reducing, and anti-oxidant benefits. Add to this green tea’s possible reduction of heart attack risk.

Dr Shinichi Kuriyama of Tohuku University Graduate School of Medicine, Japan, reported their huge experience of tracking more than 40,000 people in Japan, a population accustomed to drinking green tea. Over 11 years, a total of 829 people died of heart disease. Dr. Kuriyama and associates reported that participants drinking five or more cups of green tea per day experienced 16% less risk for heart attack and death from heart disease than participants who drank only a single cup per day.

Interestingly, the largest protective effect of green tea was on stroke risk, with a nearly 40% reduction in the ≥5 cup per day group. Women also enjoyed a greater protective effect than men.

Should we all drink green tea?

Dr. Kuriyama notes that, based on the Japanese study, the effect of green tea "appears to be a threshold effect rather than a dose-response relationship, such that persons who consume at least one cup a day may receive some benefit." In other words, if you’re contemplating adding green tea to your diet, even a single cup per day may provide significant benefits.

Despite its observational nature (i.e., no treatment or placebo was introduced), this study nonetheless provides powerful information by virtue of the large number of participants and the duration of the observation period. Genuine confirmation of a heart protecting effect for green tea, however, will require a treatment vs. placebo design in a large number of people (since a disease is presumably being prevented, not treated) over many years. But the design of this study represents a compromise that, when added to the existing experience with green tea, suggests that it truly provides health effects.

Add the Japanese study to the expanding list of interesting observations surrounding green tea. Among other proposed health benefits of green tea or its principal ingredients, theaflavin and epigallocatechin, are:

• Reduction of total and LDL cholesterol (Maron DJ et al 2003).
• Reversal of abnormal artery constriction (endothelial dysfunction) (Kim W et al 2006).
• Anti-inflammatory effects, such as suppression of the inflammatory mediator, nuclear factor kappaB (Syed DN et al 2006).
• Anti-cancer or cancer preventing effects (“chemoprevention”) (Yang CS et al 2006).

Green tea is inexpensive and available. Many Americans simply haven’t caught onto the habit of tea drinking, but cold pre-brewed teas are also appearing on the market. Though pre-brewed teas tend to have substantially less catechin and flavonoid content than freshly brewed teas, they make a reasonable second choice. The best choice is green tea, higher in flavonoids and catechins than black tea, and brewed for 3–5 minutes to extract maximum active ingredients.

Should you stop your fish oil, niacin, oat bran, and exercise program in favor of green tea? Absolutely not! Taken in the perspective of coronary plaque control, green tea only offers the possibility of slight advantage. It will not achieve control or reduction of coronary plaque as a stand-alone treatment. But if you’d like an interesting, versatile beverage that can be served hot or cold, with lemon or spices like ginger and mint, and may provide some heart protection benefits, drink up!

References:

Kim W, Jeong MH, Cho SH et al. Effect of green tea consumption on endothelial function and circulating endothelial progenitor cells in chronic smokers. Circ J 2006 Aug;70(8):1052–1057.

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; 296:1255-1265.

Maron DJ, Lu GP, Cai NS, Wu ZG, Li YH, Chen H, Zhu JQ, Jin XJ, Wouters BC, Zhao J. Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial. Arch Intern Med. 2003; 163:1448–1453.

Syed DN, Afaq F, Kweon MH et al. Green tea polyphenol EGCG suppresses cigarette smoke condensate-induced NF-kappaB activation in normal human bronchial epithelial cells. Oncogene 2006 Jul 24; [Epub ahead of print]

Yang CS, Lambert JD, Hou Z, Ju J, Lu G, Hao X. Molecular targets for the cancer preventive activity of tea polyphenols. Mol Carcinog 2006 Jun;45(6):431–435.
 

Copyright 2006, Track Your Plaque.