Study Finds Tea Provides 50% of Flavonoid Antioxidants in
From Expressly My Health
At the American Dietetic Association's (ADA) annual Nutrition News Forecast meeting, new findings reported by a research team from Michigan State University claiming that tea is the major source of flavonoid antioxidants in the U.S. diet, supplying 55% of the estimated 134 mg/day in the U.S. diet.
Clinical studies have shown that tea flavonoids may promote good heart health by improving endothelial function and by reducing blood cholesterol levels.
"These findings are encouraging and indicate a need for further investigation of the relationship between flavonoid intake and prevalence of chronic diseases," said Won O. Song, PhD, MPH, RD, a CoPI and senior researcher at Michigan State University. "Tea was identified as the most significant source of flavonoid antioxidants in the U.S. diet. This means that we may be able to realize health benefits by doing something as simple as drinking more tea."
Until the MSU study was reported, flavonoid intake in a free-living population has not been estimated adequately or consistently. The study aimed to estimate flavonoid intake of the U.S. population and of specific subgroups as well as to identify the major dietary food sources of flavonoids.
The researchers matched the recently released flavonoid contents of the United States Department of Agriculture (USDA) Flavonoid Databases with the dietary intake data from the most recent consumption figures representative of the total U.S. population from the U.S. National Health and Nutrition Examination survey (NHANES) of 1999-2002.
The researchers estimated the sum of 24 flavonoid compounds within the U.S. population diet and found the major flavonoids in order of amount were flavanols, flavonol, flavanones, flavones, anthocyanidins and isoflavones. Teas, which are rich in flavanols were identified as the most significant source of flavonoids in the U.S. diet, contributing 74 mg of daily flavonoid intake. Other major food groups contributing to flavonoid intake include fruits; vegetables; and the bread, cereals, rice and pasta group.
It is thought that any health effects from tea drinking may stem from its antioxidant content. "Several studies have found that tea drinking may be good for the heart, " said Douglas Balentine, PhD, director nutrition sciences, Unilever Health Institute. "For most Americans, drinking a cup of tea a day - hot or cold - will increase their daily flavonoids by over 50%. This in turn, may further reduce risk for chronic diseases."
A number of population studies conducted around the world including studies in the United States and Europe have consistently found that drinking black tea is associated with a reduced risk of heart disease. Three separate analyses of research indicated that drinking three cups of tea daily was associated with about a 10 to 12% lower risk of cardiovascular disease death or heart attack in the populations studied.
One of these analyses reviewed 17 population studies and assessed the relationship between tea drinking and stroke, heart attack, and all types of coronary heart disease. Results showed that the rate of heart attack decreased by 11% among those who drank three cups of tea per day.
A second analysis included seven studies and evaluated consumption of dietary flavonoids and risk of death from heart disease. Reported in the European Journal of Clinical Nutrition, investigators found a 20% reduction in risk of death from coronary heart disease among study participants who consumed the most dietary flavonoids (tea was the primary source of flavonoids) when compared to study participants who consumed the least dietary flavonoids. A third review of 10 studies showed that drinking around three cups of tea each day was associated with reduced incidence of heart attack (11%) and reduced rate of death from heart disease (11%).
Since heart disease is a complex disease with multiple risk factors there are several possible roles tea may play that might explain the reduced risk of disease observed in people consuming black tea. For example, clinical studies have suggested that tea flavonoids may promote good heart health by improving endothelial function.
Together, these studies provide growing support that drinking tea regularly may help maintain a healthy heart, as part of a healthy lifestyle. At this time, these studies are not conclusive and further research needs to be done. Tea should be consumed as part of a balanced diet containing a wide variety of fruits, vegetables and whole-grain products.
