Green and Black Tea: Literature in Review
A double blind, randomized controlled trial was conducted to examine the effects of black tea extract as a dietary supplement in participants with borderline hypercholesterolemia (1). Over 3 months, 47 participants consumed either 333 mg of black tea extract or 333 mg of placebo, three times daily before each meal. Blood samples were taken prior to ingestion, in addition to 1, 2, and 3 months after ingestion. Blood samples were analyzed for triacylglycerol (TG), total cholesterol, HDL, LDL, fasting blood glucose, creatinine, C-reactive protein, and various enzymes. Compared to the participants assigned to the placebo, those assigned to the black tea extract experienced a significant increase in HDL (“good” cholesterol) and a significant decrease in mean total cholesterol, LDL (“bad” cholesterol), mean body weight, and TG levels. Furthermore, TG and total cholesterol levels remained significant one month after supplementation was stopped. The authors of this study concluded that black tea extract has advantageous effects on patients with borderline hypercholesterolemia. Findings indicate that black tea extract may be useful not only for improving total blood cholesterol and LDL but also for preventing metabolic syndrome in subjects at risk for heart disease or obesity.
A double blind, randomized controlled trial investigated whether or not green tea supplementation has an effect on insulin resistance and other cardiovascular factors in 56 obese, hypertensive patients (2). Participants consumed a daily supplement of either 379 mg of green tea extract or 379 mg of placebo for 3 months. At baseline and after 3 months of treatment, outcome measures were assessed. Compared to the placebo, blood pressure, total cholesterol, fasting blood glucose, insulin levels, insulin resistance, LDL, TG, TNF-α, and C-reactive protein were significantly decreased in green tea extract participants, while total antioxidant status and HDL were significantly increased. The findings of this study suggest that green tea extract supplementation could be an effective strategy to improve blood pressure, insulin resistance, inflammation, oxidative stress, and lipid profile in patients with obesity-related hypertension.
The findings of both studies provide ample evidence that both green and black tea extract can have an advantageous effect on individuals who are vulnerable to cardiovascular complications. For more information, visit the American Heart Association.
References
(1) Fujita H, Yamagami T. Efficacy and safety of Chinese black tea (Pu-Ehr) extract in healthy and hypercholesterolemic subjects. Ann Nutr Metab. 2008; 53(1):33-42.
(2) Bogdanski P, Suliburska J, Szulinska M, Stepien M, Pupek-Musialik D, Jablecka A. Green tea extract reduces blood pressure, inflammatory biomarkers, and oxidative stress and improves parameters associated with insulin resistance in obese, hypertensive patients. Nutr Res. 2012; 32(6):421-7.
Written by Nicole Lindel, MS in Nutrition Education from Columbia University