Effect of black tea intake on blood cholesterol concentrations in individuals with mild hypercholesterolemia: a diet-controlled randomized trial

Abstract

Habitual intake of black tea has been associated with relatively lower serum cholesterol concentrations in observational studies. However, clinical trial results evaluating the effects of black tea on serum cholesterol have been inconsistent. Several factors could explain these mixed results, in particular, uncontrolled confounding caused by lifestyle factors (eg, diet). This diet-controlled clinical trial estimates the effect of black tea flavonoid consumption on cholesterol concentrations in 57 borderline hypercholesterolemic individuals (total cholesterol concentrations between 190 and 260 mg/dL [4.9 and 6.7 mmol/L]). A double-blind, randomized crossover trial was conducted in Minneapolis, MN, from April 2002 through April 2004 in which key conditions were tightly controlled to minimize possible confounding. Participants consumed a controlled low-flavonoid diet plus 5 cups per day of black tea or tea-like placebo during two 4-week treatment periods. The flavonoid-free caffeinated placebo matched the tea in color and taste. Differences in cholesterol concentrations at the end of each treatment period were evaluated via linear mixed models. Differences among those treated with tea vs placebo were 3.43 mg/dL (0.09 mmol/L) (95% CI -7.08 to 13.94) for total cholesterol, -1.02 mg/dL (-0.03 mmol/L) (95% CI -11.34 to 9.30) for low-density lipoprotein cholesterol, 0.58 mg/dL (0.02 mmol/L) (95% CI -2.98 to 4.14) for high-density lipoprotein cholesterol, 15.22 mg/dL (0.17 mmol/L) (95% CI -40.91 to 71.35) for triglycerides, and -0.39 mg/dL (-0.01 mmol/L) (95% CI -11.16 to 10.38) for low-density lipoprotein plus high-density lipoprotein cholesterol fraction. The low-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio decreased by -0.1 units (95% CI -0.41 to 0.21). No results were statistically or clinically significant. The intake of 5 cups of black tea per day did not alter the lipid profile of borderline hypercholesterolemic subjects significantly.

Trial registration: ClinicalTrials.gov NCT01882283.

Keywords: Black tea; Flavonoids; Hypercholesterolemia; Randomized crossover controlled trial; Serum lipids.

Figure 1

Crossover study design overview, including timing of biological sample collection points, in a study of the effect of 5 cups per day of black tea on serum cholesterol concentrations (n=57)