A clinical trial testing a theaflavin-enriched green tea extract is the first human study to find that a tea product lowers cholesterol.
The study included 240 men and women with high cholesterol levels in China. During the 12-week trial, participants, already on a low-fat diet, were randomly chosen to receive either a placebo or a 375 mg soft gel capsule containing green and black tea extracts enriched with the antioxidant theaflavin.
The results, reported in the Archives of Internal Medicine, surprised lead author Dr. David J. Maron, associate professor of Medicine at Vanderbilt University Medical Center.
"Personally, I was very surprised," Maron said. "I expected, if anything, a very slight cholesterol-lowering effect. But what we saw was a 16 percent reduction in low density lipoprotein (LDL) cholesterol."
Tea is the second most widely consumed beverage worldwide. In the past, several epidemiologic studies had shown that tea consumption is associated with lower cholesterol. Experiments in animals have demonstrated that green tea, black tea, and flavonoids derived from green and black teas lower cholesterol.
However, previous tea-drinking experiments in humans, as well as those experiments involving the administration of green tea extract, have failed to show any effects on cholesterol.
The 375 mg capsule used in this study is an extract made up of 75 mg of theaflavins (flavonoids from black tea), 150 mg of catechins (flavonoids from green tea) and 150 mg of other tea antioxidants called polyphenols. It is equivalent to 35 cups of high-quality black tea and seven cups of green tea.
The National Cholesterol Education Program recommends eating a low-fat, low-cholesterol diet with more viscous fiber and switching from butter to margarine with the natural plant compound stanol, as the initial therapy for lowering LDL cholesterol in people without heart disease, said Maron.
Maron said there is a need to identify additional non-drug options for lowering cholesterol that have sufficient safety and efficacy data. There is also a need to find products that are more practical for the consumer than viscous fiber and foods made with plant stanols, he said.
"The present study represents the first step in establishing the practicality, safety and LDL-lowering ability of this tea product," Maron said.
While pleased with the initial outcomes, he recommends further testing to determine long-term safety, the effective dosing range, the impact when the extract is taken with lipid medication (especially statins) and the adaptability to other ethnic and patient groups.
"Although the results are exciting, we do not want people to take the extract in place of their medications," he said. "Unlike statins, this product has not been proven to prevent heart attacks or stroke, or to prolong life. The study shows that the tea extract is a useful adjunct to lowering LDL in people with high cholesterol already on a low-fat diet."