Lead cook Sue Burns instructs volunteers before
they eat dinner and drink tea, which is part of a tea nutrition study. Click
image for additional information.
Tea Consumption Lowers Blood Cholesterol
By Rosalie Marion
September 30, 2003
Drinking tea lowered low-density
lipoprotein, the LDL "bad" cholesterol, in a small group of
volunteers in an Agricultural Research Service study reported in the October
issue of the Journal of
Nutrition. The study was led by research chemist Joseph T. Judd with
the agency's Diet and Human
Performance Laboratory, one of seven laboratories at ARS'
Beltsville Human Nutrition Research
Center. ARS is the U.S. Department of
Agriculture's chief scientific research agency.
"These findings illustrate the impact of specific types of
health-promoting phytonutrients on the diet," said Ed Knipling, Acting
Administrator for ARS.
Judd's study assessed the effects of black tea consumption on blood lipid
concentrations in adults with mildly high cholesterol. Seven men and eight
women were given five servings of black tea per day for three weeks, and a
tea-flavored water for another three-week period. In a third study period,
caffeine was added to the tea-flavored water in an amount similar to that found
in the tea.
"Overall, we found a 6 to 10 percent reduction in blood lipids in black
tea drinkers in just three weeks," said Judd. The study showed no effect
on high-density lipoprotein, the HDL "good" cholesterol. The study's
authors concluded that drinking black tea, in combination with following a
prudent diet moderately low in fat, cholesterol and saturated fatty acids,
reduces total and LDL cholesterol by significant amounts and may reduce the
risk of coronary heart disease.
While several previous studies based on population surveys revealed a link
between green and black tea consumption and reduced risk of coronary heart
disease, experimental clinical studies failed to confirm effects of tea
consumption on risk factors for coronary heart disease. According to Judd, many
of those studies may not have adequately controlled the background diets of the
volunteers. "Other foods or nutrients consumed during the studies could
have affected the risk factors," he said.
The Camellia sinensis plant is the source of three major classes of
teas known as green, black and oolong. Unlike herbal teas, these teas contain
caffeine, unless decaffeinated. About 90 percent of tea consumed in the United
States is black. Green tea contains more simple antioxidant flavonoids, while
black tea contains more complex varieties.
Judd's study appears in the October Journal of Nutrition among other
proceedings from the Third International Scientific Symposium on Tea and Human
Health held at USDA last year in Washington, D.C. Research on the effects of
antioxidant phytonutrients in tea on coronary heart disease risk is ongoing at
the Beltsville Human Nutrition Research Center.