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

• E-mail
• Print
• Link

Although there was a one-percent decrease in body weight for every one-percent increase in RMR with caffeine and ephedra, the rise in metabolic rate is only responsible for 25 percent of the weight loss. (7) In addition to causing an increase in metabolic rate, caffeine and ephedra consumption decreases food intake, accounting for the other 75 percent of the weight loss seen in the caffeine and ephedra study. Since both the caffeine with ephedra supplement and the black tea supplement appear to work via the adrenergic nervous system, the presumption could be made that the proportion of weight loss due to increase in thermogenesis and decrements in food intake would be similar in the two studies.

In contrast to a trial with green tea, the respiratory quotient was not decreased in this study. (2) This suggests the black tea extract and caffeine in the supplement increased fat oxidation in proportion to the oxidation of other substrates. The rise in temperature, although not statistically significant, is consistent with an increase in metabolic rate.

The supplement appeared to be well tolerated. The only potential safety concern raised by this study was the increase in systolic blood pressure, an average of 3-4 mm Hg. In a clinical trial of caffeine with ephedrine, blood pressure reached placebo levels by the eighth week of treatment, possibly due to down-regulation of the adrenergic receptors. (8) It is possible a similar situation would prevail with black tea extract and caffeine. Furthermore, increases in SBP after an acute dose of caffeine have been well documented. Acute administration of 100-360 mg of caffeine to normotensive subjects is reported to result in SBP increases ranging from 2-14 mm Hg. (9) The increase in SBP seen in the present study is in keeping with the published literature.

Conclusion

This preliminary study confirms the rise in metabolic rate after one hour, and over two hours as measured by AUC with an herbal supplement containing black tea and caffeine. It suggests potential for the supplement to cause weight loss with longer-term treatment. The modest significant rise in systolic blood pressure can be attributed to the known pressor effect of caffeine. Although it is likely there would be a lessening of this effect on blood pressure with chronic treatment, confirmation of this presumption and that of weight loss await a longer-term clinical trial.

Acknowledgements

The authors would like to acknowledge Numico Research who awarded the grant that funded this study.

References

(1.) Chantre P, Lairon D. Recent findings of green tea extract AR25 (Exolise) and its activity for the treatment of obesity. Phytomedicine 2002;9:3-8.

(2.) Dulloo AG, Duret C, Rohrer D, et al. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr 1999;70:1040-1045.

(3.) Dulloo AG, Seydoux J, Girardier L, et al. Green tea and thermogenesis: interactions between catechin-polyphenols, caffeine and sympathetic activity. Int J Obes Relat Metab Disord 2000;24:252-258.