The effect of an herbal supplement containing black tea and caffeine on metabolic parameters in humans

Alternative Medicine Review, Dec, 2005 by Andrew T. Roberts, Lilian de Jonge-Levitan, Catherine C. Parker, Frank L. Greenway

Abstract

OBJECTIVE: The objective of this study was to test an herbal supplement containing black tea (the fully oxidized form of Camellia sinensis) and caffeine for stimulation of thermogenesis.

METHODS/MATERIALS: A double-blind, placebo-controlled, crossover study was conducted on 16 healthy, weight-stable, non-smoking subjects, ages 21-55 years, with body mass index (BMI) of 20-30 kg/[m.sup.2], and on no medications other than oral contraceptives or hormone replacement therapy. Subjects had no caffeine for 48 hours, no exercise for 24 hours, and no food for 12 hours before each visit. Area under the curve (AUC) for resting metabolic rate (RMR), respiratory quotient (RQ), blood pressure, pulse rate, and temperature were measured. At each visit RMR was measured at baseline and at one and two hours following oral administration of a supplement containing principally 600 mg black tea extract (60% polyphenols, 20% caffeine) and 442 mg guarana extract (36% caffeine) or matching placebo.

RESULTS: The RMR and systolic blood pressure (SBP) AUCs increased significantly (p<0.02 and p<0.01, respectively) in the herbal supplement group compared to placebo. The AUC increase in RMR over the two-hour test period was 77.19 kcal/24 [hr.sup.2] [+ or -] 120.10 kcal/24 [hr.sup.2] with an average rise of 52.38 [+ or -] 29.52 kcal/24 hrs. The AUC rise in SBP over two hours was 10.3 mm Hg/hr [+ or -] 14 mm Hg/hr. The average rise in SBP over two hours was 3.7 mm Hg [+ or -] 4.4 mm Hg.

DISCUSSION: The herbal supplement increased metabolic rate without changing substrate oxidation. The rise in SBP was consistent with the amount of caffeine the supplement contained.

Introduction

Tea, a water extract of Camellia sinensis L., is a beverage widely consumed around the world. Tea is processed into at least three types: green, oolong, and black. Green tea is the non-oxidized and non-fermented form and contains several polyphenolic components, including epigallocatechin gallate. (1) Dulloo et al found epigallocatechin gallate at a dose of 270 rag/day increased resting metabolic rate when combined with 150 mg/day caffeine, compared to placebo. The same was not true for caffeine 150 mg/day alone. (2) The combination of epigallocatechin gallate and caffeine also synergistically increased the oxygen consumption of brown fat cells in vitro. (3)

Although oolong tea decreases weight gain in rodents on a high-fat diet, oxidation of tea has been thought to impair its efficacy in treating obesity. (4) Oolong tea is partially oxidized; oxidation is halted by bruising and pan frying the leaves. Black tea, the fully oxidized form of tea, has not been tested for its effect on oxygen consumption, presumably because of the belief that fully oxidized tea would no longer contain the compounds needed to increase metabolic rate. This trial tests the ability of black tea extract in combination with caffeine and other ingredients in the TeaLean[R] supplement (Numico Research; Boca Raton, Florida) to increase oxygen consumption in humans.

Methods and Materials Subject Inclusion/Exclusion

Sixteen healthy males and non-pregnant, non-nursing females, ages 21-55 years with a BMI from 20-30 kg/[m.sup.2] who ate meals at regular intervals, were included in the study. Good health was assessed by a medical history, physical examination, electrocardiogram, chemistry panel (glucose, creatinine, iron, sodium, potassium, chloride, uric acid, calcium, total protein, phosphorus, albumin, globulin, albumin/globulin ratio, total bilirubin, alkaline phosphatase, gamma-glutamyl transpeptidase, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase), lipid profile (cholesterol, triglycerides, HDL cholesterol, and LDL cholesterol), thyroid stimulating hormone, complete blood count, urinalysis, and a pregnancy test in women with childbearing potential. For study inclusion, lab values, medical history, and physical examination findings were to be within normal limits. The occasional participant with values just outside the normal limits, but not believed to be clinically significant, was allowed to enroll in the study.

Smokers, users of nicotine, subjects taking chronic medications other than oral contraceptives or hormone replacement therapy, subjects who lost or gained more than 4 kg in the preceding three months, and subjects taking ephedra-containing products were specifically excluded from the study. The study was reviewed and approved by a local Institutional Review Board, and those included in the study reviewed and signed a written informed consent form. Characteristics of subjects accepted into the study are shown in Table 1.

Study Visits

Subjects reported to the Pennington Center on two occasions during the study following the screening process. Before each visit the subjects fasted for 12 hours, refrained from strenuous physical activity for 24 hours, ate a normal diet, and avoided alcohol or caffeine-containing beverages for 48 hours. The study visits were separated by 7 [+ or -] 2 days. On each visit, the subject rested for 30 minutes prior to measurement of resting metabolic rate (RMR), respiratory quotient (RQ), systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse, and temperature. Metabolic rate and respiratory quotient were measured for 30 minutes after the resting period by indirect calorimetry using a ventilated hood system (DeltaTrac II metabolic monitor; Datex Inc.; Helsinki, Finland)? During this procedure, a transparent ventilated hood is placed over the subject's head and the amount of oxygen consumed and carbon dioxide exhaled is analyzed by the system.