Nov. 16, 1999 ATLANTA, Nov. 10 -- Westernized Chinese are moving away from the traditional diet rich in vegetables and green tea, and instead adopting the typical "American diet" that contains larger amounts of animal fats -- a dietary shift that may be increasing their risk of heart disease and stroke. That's according to a study presented today at the American Heart Association Scientific Sessions.
Villagers in Pan Yu, a town in Guangdong Province in southern China, emphasize the traditional Chinese diet of vegetables, rice and green tea, says Kam S. Woo, M.D., professor and consultant cardiologist at the Chinese University of Hong Kong. Woo believes it is no coincidence that the area also has one of the lowest rates of heart disease in the world.
In a new study, westernized Chinese individuals in Hong Kong, Sydney, Australia, and San Francisco, Calif., had thicker inner walls in their carotid arteries (located in the neck) than study participants in Pan Yu -- a sign that the westernized Chinese study participants are developing atherosclerosis, a thickening of artery walls often accompanied by fatty plaque blockages that, together, increase the risk of heart attack and stroke.
Woo says the message in the study is that Chinese and non-Chinese alike should recognize the protective effects of a traditional Chinese diet.
"Perhaps people need to eat more fruits and vegetables, emphasize plant proteins and eat less dairy products and meat," he says. "They should also consider adopting a Chinese way of cooking, which involves lots of steaming as opposed to deep frying in oil."
While these dietary recommendations are similar to those of health organizations, including the American Heart Association, the Chinese diet also includes tofu and green tea, components whose heart-protecting effects are still uncertain.
Researchers are not sure how green tea might protect against heart disease. But Woo says it may have something to do with the antioxidants in the beverage. Antioxidants, which are found in vitamins and foods, are thought to fight heart disease by counteracting oxygen free-radicals. Oxygen free-radicals are unstable molecules that can combine with cholesterol to form oxidized cholesterol. In this form, cholesterol is more likely to collect on the blood vessels, forming fatty deposits that lead to heart attacks and strokes.
Researchers studied 116 Chinese individuals ages 20 to 60. The group was 56 percent female and 44 percent male. Researchers used ultrasound, an imaging device that uses sound waves, to determine the thickness of the inner walls of the carotid arteries that feed blood to the brain. The study participants also answered questions about their dietary habits.
The combined thickness of the intima (lining) and media (middle muscle) layers of the carotid artery are considered a good indicator of heart disease. In healthy adults 65 or older, increased thickness correlates with a higher risk of heart attack and stroke, while in younger adults, with no symptoms of heart disease, thicker intima-media reflects the probable development of atherosclerosis.
The surveys revealed wide differences in eating patterns, especially in the consumption of meat. In Pan Yu, villagers consumed about 13 grams of meat protein daily per 1,000 calories, along with about 3 grams of dairy products and 151 grams of vegetables. (Thirty grams equal one U.S. ounce.) They also drank about 14 ounces per day of green tea.
In San Francisco, westernized Chinese consumed about 24 grams of meat protein, 51 grams of dairy products, 117 grams of vegetables and 37 milliliters, or less than a quarter-cup, of green tea daily per 1000-calorie intake.
The average carotid inner wall thickness was about one-fifth thinner among the Pan Yu participants than among those in San Francisco, says Woo. What do Chinese in Pan Yu eat? Typically, mornings start with congee -- a rice porridge -- Chinese buns or dumplings, each serving of which might contain an amount of meat equivalent to a small spoonful. "Hardly any ham, bacon, sausage or scrambled egg is eaten in the typical Pan Yu breakfast meal," Woo says. Lunch and dinner consist of two bowls of rice with steamed or stir-fried vegetables, again with a small amount of meat, steamed fish or tofu. If eggs are served, typically two are scrambled and four people will share them.
In contrast, Chinese in mainland cities are consuming more meat and dairy products, and even enjoy ice cream -- a particular favorite of the younger generation. "It is our great concern, that what has happened to many western Chinese will happen to many westernized mainland Chinese in the next one to two decades," he says. Still, "as long as they retain the traditional dietary pattern of high vegetable and plant protein consumption, they may be protected."
One indication that this may be so relates to fat consumption. Pan Yu villagers' fat and cholesterol intake was no lower than those in other Chinese communities, Woo says -- and in fact, may be higher -- but Pan Yu still had the advantage in reduced heart disease. However, Chinese home cooking is typically lower in fat than the average Western diet.
Woo says other research is planned to look at such questions as whether green tea is more protective than black tea. "Our collaborative project will provide a unique opportunity to identify adverse and protective dietary and lifestyle factors, and the underlying mechanisms that may predispose westernized Chinese to heart disease," Woo says. "It will also contribute an overall better understanding of how we might use dietary means to help prevent heart disease in Westernized Chinese and Americans."
Co-authors include Ping Chook, M.D.; Belinda Liu, B.Sc.; Jean L. F.Woo, M.D.; Shu W. Chan, M.D.; Jian Z. Feng, M.D.; Olli T. Raitakari, Ph.D.; and David S. Celermajer, M.D.
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