Consuming 30-32oz of tea daily over a period of time -- the fluid equivalent of 2.5 cans of soda -- may reduce Low Density Lipoprotein (LDL, or "bad") cholesterol levels by more than 10 percent and decrease the risk of DNA damage caused by smoking, according to new research study.
These and other studies, including government research utilizing emerging biomarkers of cardiovascular health, are included in the supplement titled Proceedings of the Third International Scientific Symposium on Tea and Human Health: Role of Flavonoids in the Diet and provide further evidence of tea's disease-fighting potential in the areas of cardiovascular health and cancer.
Researchers at the United States Department of Agriculture (USDA) Beltsville Human Nutrition Research Center in Beltsville, MD, studied the effect of five six-ounce servings per day of either black tea, a caffeine-free placebo or caffeinated placebo beverage in 15 mildly hypercholesterolemic adults for three weeks. The volunteers followed a "Step I" type diet, moderately low in fat and cholesterol, as described by the American Heart Association and the National Cholesterol Education Program during the trial.
After three weeks, the researchers examined participants' lipid profiles, including total cholesterol, LDL cholesterol, as well as two emerging biomarkers for cardiovascular health which some scientists argue could provide more in-depth measures of individual cardiovascular disease risk than LDL and TC alone: Apolipoprotein B (ApoB) and Lipoprotein(a) [Lp(a)].
Levels of ApoB decreased by 5 percent and levels of Lp(a) fell by 16.4 percent. ApoB concentrations reflect the number of LDL "particles" in the arteries, providing a more specific measure of LDL cholesterol levels. Lp(a) are lipoprotein particles that contain a particular protein which could potentially interfere with the body's ability to dissolve blood clots. Some scientists believe that a reduction in Lp(a) levels suggests a benefit to cardiovascular health. This reduction in Lp(a) could be important because most standard cholesterol treatments have little effect on this lipoprotein. This is an emerging biomarker which may become an important risk factor not reflected in LDL or TC measures, because of the role blood clots play in the risk of stroke and myocardial infarction.
One possible mechanism for this effect is tea's potential ability to limit cholesterol absorption in the intestines.
Led by Arizona College of Public Health, University of Arizona and Arizona Cancer Center in Tucson, Arizona, researchers studied the effect on 143 heavy smokers of consuming four eight-ounce servings per day of either decaffeinated green tea, decaffeinated black tea or water for four months. The results showed that the levels of 8-OHdG, an indicator of oxidative DNA damage, dropped by a significant 31 percent after four months in those in the green tea group, but not in the other two groups. Oxidative DNA damage is implicated as a contributor to cancer development as well as cardiovascular disease.
Smokers were selected as participants due to the high levels of oxidative DNA damage cigarette smoking causes, making changes in those levels easy to detect. Researchers believe that the process of decaffeination affects black tea much more than green tea, thus the black tea may have been weakened because many of the flavonoids had been removed.