Extracts from black tea may reduce total cholesterol levels by nine per cent and LDL cholesterol levels by 12 per cent, according to a new study from Japan. Consumption of the black tea extract (BTE) was also associated with beneficial changes in blood levels of triglycerides and body weight, according to results published in the journal Nutrition Reviews.
High cholesterol levels, hypercholesterolaemia, have a long association with many diseases, particularly cardiovascular disease (CVD), which is the number one killer on both sides of the Atlantic.
"The present study is the first to report that BTE (one gram per day) significantly lowered total cholesterol and LDL cholesterol levels in human subjects with borderline hypercholesterolemia in a randomised double-blind placebo-controlled study," wrote authors Hiroyuki Fujita and Tomohide Yamagami from the R&D Department of Nippon Supplement in Osaka.
The study involved 47 people with borderline hypercholesterolaemia assigned to receive the BTE or placebo for three months.
The health benefits of tea have been linked to the polyphenol content of the tea. Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidised by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
Study details
The subjects, aged from 40 to 70 years, were randomly assigned to receive the black tea extract (one gram per day) or placebo for three months. The subjects consumed the pills before a meal.
After three months, a 9 per cent reduction in total cholesterol was observed in the tea extract group, from 6.14 to 5.62 moles per litre at the start and end of the study, respectively. Furthermore, LDL cholesterol levels fell by 12 per cent, from 4.32 to 3.81 moles per litre.
Similar reductions in triglyceride levels were observed, but no significant changes in any blood lipid levels were recorded in the placebo group.
"Interestingly, the reduced levels of total cholesterol, LDL cholesterol, and TG levels remained significant even one month after termination of black tea extract intake," wrote Fujita and Yamagami.
The authors also note no "undesirable changes in other biochemical parameters", such as fat-soluble vitamins. Moreover, none of the subjects reported any adverse effects from consumption of the black tea extracts.
Mechanism
Fujita and Yamagami postulated that the tea extract may function by inhibiting the reabsorption of bile acids. By binding to the bile acids the extracts increase the excretion of cholesterol - the liver compensates by producing more bile from cholesterol, thereby promoting cholesterol lowering.
"Because the black tea extract induces the precipitation of mixed bile salt micelles and lowers blood cholesterol levels, it might have contributed to body weight loss in this study," they wrote.
"In this regard, further investigation of black tea extract effects on body weight loss is warranted," they concluded.
They also stated that future studies should investigate if the extract can play a role in reducing arteriosclerosis related to the metabolic syndrome and obesity in humans.
Source: Nutrition Research (Elsevier)
July 2008, Volume 28, Issue 7, Pages 450-456
"Antihypercholesterolemic effect of Chinese black tea extract in human subjects with borderline hypercholesterolemia"
Authors: H. Fujita, T. Yamagami
