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  • Green Tea Extract for fat loss: An interview with researcher Dr. Abdul Dulloo

    Posted by .(JavaScript must be enabled to view this email address)
    Monday, April 05, 2004 12:23 pm Email this article
    "An extract of Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content," says obesity researcher Abdul Dulloo, M.D., Ph.D. from the Institute of Physiology at the University of Fribourg in Fribourg, Switzerland.

    Dr. Dulloo is lead author of a recent paper appearing in the American Journal of Clinical Nutrition which found that green tea exact increases both fat oxidation and daily calories burned. Larry Hobbs interviewed Dr. Dulloo via email.


    Dulloo AG; Duret C; Rohrer D; Girardier L; Mensi N; Fathi M; Chantre P; Vandermander J. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. American Journal of Clinical Nutrition, 1999 Dec; 70(6):1040-5.

    Calories Burned

    Hobbs: Does green tea extract increase calories burned?

    Dulloo: Yes. The 24-hour energy expenditure was 3.5 percent greater on average—an increase of 70 kilocalories per day—when patients were given green tea compared to when they were given placebo compared to only 0.6 percent greater than when they were given caffeine.

    Hobbs: How much did it vary among subjects?


    The Range Of Calories Burned

    Dulloo: Considerably. It ranged from and increase of 64 kilocalories to 200 kilocalories per day among the subjects. Six out of 10 subjects showed an increase in calories burned when given green tea compared to when they were given placebo.


    Green Tea Vs Caffeine Alone

    Hobbs: How does this compare to caffeine?

    Dulloo: In a previous study we found that much larger doses of caffeine—600 mg per day—caused a similar increase of 96 calories per day, but no increase was found in the present study when only 150 mg of caffeine was administered.


    Dulloo AG; Geissler CA; Horton T; Collins A; Miller DS. Normal caffeine consumption: influence on thermogenesis and daily energy expenditure in lean and postobese human volunteers. American Journal of Clinical Nutrition, 1989 Jan, 49(1):44-50.


    Green Tea Vs Ephedrine And Caffeine

    Hobbs: How does this compare to the combination of ephedrine and caffeine?

    Dulloo: The increase was twice as great with ephedrine, caffeine and theophylline. That combination increased calories burned by 8 percent per day which in our study was equivalent to 191 kilocalories per day.


    Dulloo AG; Miller DS. The thermogenic properties of ephedrine/methylxanthine mixtures: human studies. International Journal of Obesity, 1986, 10(6):467-81.


    Fat Oxidation

    Hobbs: Does green tea extract increase fat oxidation?

    Dulloo: Yes. In fact, the increase in fat oxidation was even more consistent than the increase in energy expenditure. Whereas 6 out of 10 subjects showed a significant increase in calories burned, 8 out of 10 showed a significant increase in fat oxidation.

    Hobbs: How much of an increase in fat oxidation was there?

    Dulloo: About 10 percent of calories burned. That is 41.5 percent of calories burned per day came from fat when subjects were given green tea extract compared to 31.6 percent when they were given placebo.

    The increase in fat oxidation was at the expense of carbohydrate oxidation, that is more fat was burned and less carbohydrates were burned.

    Carbohydrate oxidation decreased from 55 percent of calories burned to 45 percent.

    There was no change in the amount of protein burned.

    For the men in our study who burned approximately 2200 calories per day this means that they burned 220 more fat calories and 220 fewer carbohydrate calories.


    Caffeine Alone Does Not Increase Fat Oxidation

    Hobbs: Does caffeine increase fat oxidation?

    Dulloo: No. In our study, caffeine given at a dose of 150 mg per day, did not increase fat oxidation.

    In another study also conducted under similar conditions in a calorimetry-chamber even doses as large as 1000 mg per day did not result in a significant increase in 24-hour fat oxidation.


    Bracco D; Ferrarra JM; Arnaud MJ; Jequier E; Schutz Y. Effects of caffeine on energy metabolism, heart rate, and methylxanthine metabolism in lean and obese women. American Journal of Physiology, 1995 Oct, 269(4 Pt 1):E671-8.

    Hobbs: Did percent body fat affect the green tea-induced increase in fat oxidation?

    Dulloo: No. We found no correlation with degree of body fat and the increase in fat oxidation.


    No Side Effects

    Hobbs: What were the side effects of green tea?

    Dulloo: No side effects were reported, however this was only a one-day study.


    Heart Rate And Blood Pressure: No Effect

    Hobbs: Was there any effect on heart rate or blood pressure?

    Dulloo: There was no effect on heart rate, however, we did not measure blood pressure.


    How Does Green Tea Increase Thermogenesis

    Hobbs: How does green tea extract increase thermogenesis?

    Dulloo: We believe that it is the result of an interaction between the two main ingredients in green tea—the catechins and the caffeine—with the noradrenaline release by the sympathetic nervous system.

    The catechins in green tea inhibit an enzyme called catechol O-methyltranferase also known as COMT which degrades noradrenaline.

    Whereas caffeine inhibits the enzyme system phosphodiesterase which degrades the levels of cAMP which is responsible for thermogenesis.

    Thus the catechins and caffeine, by inhibiting COMT and phosphodiesterase, respectively, may increase the levels of noradrenaline, potentiate its effect, and prolong the life of cAMP in the cell which results in a more sustained effect of thermogenesis.

    Hobbs: Is green tea more effective than caffeine at stimulating thermogenesis?

    Dulloo: Yes.


    Ephedrine And Green Tea Vs Ephedrine And Caffeine

    Hobbs: Is green tea more effective than caffeine at stimulating ephedrine-induced thermogenesis?

    Dulloo: Yes, at least in vitro. In fact, under these conditions—that is under conditions of stimulated noradrenaline release such as when ephedrine is administered—the effect is even more pronounced than giving green tea alone.

    Hobbs: So it is not just the catechins or not just the caffeine, but the combination of the two?

    Dulloo: Yes, that’s correct.

    It seems to be the result of an interaction between the catechins and the caffeine with noradrenaline. In an in vitro study which will be published in the December 1999 issue of International Journal of Obesity we found that the thermogenic effect of green tea could be mimicked by a combination of epigallocatechin gallate—the most potent of the catechins found in green tea—and caffeine.

    This indicates that both catechins and caffeine are probably responsible for the increase in thermogenesis.

    The literature indicates that in humans, a single oral dose of caffeine must exceed 100 mg in order to have an effect on thermogenesis and a dose of 600 to 1000 mg per day seems to be necessary to increase 24-hour energy expenditure.


    Dulloo AG; Geissler CA; Horton T; Collins A; Miller DS. Normal caffeine consumption: influence on thermogenesis and daily energy expenditure in lean and postobese human volunteers. American Journal of Clinical Nutrition, 1989 Jan, 49(1):44-50.

    Bracco D; Ferrarra JM; Arnaud MJ; Jequier E; Schutz Y. Effects of caffeine on energy metabolism, heart rate, and methylxanthine metabolism in lean and obese women. American Journal of Physiology, 1995 Oct, 269(4 Pt 1):E671-8.


    Study Subjects

    Hobbs: How many people were studied?

    Dulloo: Ten healthy young men who on average were 25-years-old and weighed 173 pounds. They were given the three treatments on three separate occasions.

    Hobbs: How were they studied?

    Dulloo: Each subject spent 24 hours in a respiratory chamber on three separate occasions each time receiving one of the three treatments.


    Dose Studied

    Hobbs: What were the three treatments?


    1) Green tea extract which contained 50 mg of caffeine and 90 mg of the tea catechin known as epigallocatechin gallate;

    2) 50 mg of caffeine; and

    3) a placebo all given in capsule form.

    Hobbs: How often were they taken?

    Dulloo: Three times per day. One dose was taken with each meal.

    Hobbs: How was the green tea extract prepared?

    Dulloo: It’s an alcohol extraction from dry tea leaves of unfermented Camellia Sinensis standardized for 25 percent tea catechins. It is a commercial preparation from Arkophara Laboratories in Nice, France called Exolise.


    Bioavailability Of Catechins

    Hobbs: How well are catechins absorbed? In your previous interview you had mentioned that the bioavailability of polyphenols (which includes catechins) in man was poor.

    Dulloo: Studies about bioavailability of polyphenols are rare, largely because of the complexity of interpreting the data. However, absorption is known to be poor and highly variable between individuals. In the study (Lee et al, 1995; Hollman et al, 1997) peak plasma levels ranged between 0.3 to 3 percent of the ingested dose.


    Lee MJ; Wang ZY; Li H; Chen L; Sun Y; Gobbo S; Balentine DA; Yang CS. Analysis of plasma and urinary tea polyphenols in human subjects. Cancer Epidemiology, Biomarkers and Prevention, 1995 Jun, 4(4):393-9.

    Hollman PC; Tijburg LB; Yang CS. Bioavailability of flavonoids from tea. Critical Reviews in Food Science and Nutrition, 1997 Dec, 37(8):719-38.



    Hobbs: What else is in green tea beside the catechin known as epigallocatechin gallate and caffeine?

    Dulloo: Green tea also contains other catechins including epigallocatechin, epicatechin and epicatechin gallate. However, over 50 percent of the catechins in green tea are epigallocatechin gallate which is believed to be the most pharmacologically active of the catechins.

    In our preparation epigallocatechin gallate represented 72 percent of the catechins.

    Tea catechins are a subclass of flavonoids.

    Among those of interest for energy metabolism are other flavonoids including quercetin, myricetins, but these exist in small quantities, and absorption is thought to be very poor.


    Green Tea’s Effect On Adrenaline, Noradrenaline, And Dopamine

    Hobbs: What effect did green tea extract have on levels of adrenaline, noradrenaline and dopamine?

    Dulloo: Noradrenaline levels were elevated after green tea compared to caffeine and placebo (219 nmol versus 187 versus 160, respectively). And there was a tendency for dopamine levels to be higher, however the difference was not statistically significant (1889 nmol versus 1578 versus 1587, respectively). But adrenaline levels were similar with all treatments (55 nmol versus 49 versus 66, respectively).

    Hobbs: Have you compared ephedrine-plus-green tea extract to ephedrine-and-caffeine for weight loss?

    Dulloo: No.

    Hobbs: Are you planning such a study?

    Dulloo: No, not at this time.


    Are Ephedrine And Ephedra Safe?

    Hobbs: Is ephedrine safe? It has been demonized as a “killer drug” by the U.S. press for the past 5 years.

    Dulloo:  There is no way to say that a drug, either chemical or herbal, is “safe”. This implies absolute safety. There is only relative safety.

    It depends on the dose as well as the drug.

    Most substances can be harmful if taken at a high enough dose, but this does not necessarily mean that they are “unsafe” when taken at a lower dose.

    However, I feel strongly that whenever a product to be taken is put on the market it should be tested for safety in serious clinical trials.

    Ephedrine has been used in Western medicine for treatment of respiratory problems for more than 50 years, and hundreds of thousands of patients have taken it and still take it for respiratory problems.

    The herb ephedra is being equated with ephedrine, but this is misleading since ephedra herbs or any extract that contains ephedrine also contains numerous other pharmacologically active substances, and the latter—that is the herb ephedra—could alone or in combination be the cause of adverse effects.

    Ephedrine alone or in combination with caffeine has gone through several serious placebo-controlled clinical trials for safety and efficacy as anti-obesity agents over the past 10 years (see the International Journal of Obesity, 1993 Feb, 17 Suppl 1:S1-S78), but ephedra-extracts—which again contains many other pharmacologically active ingredients—have not been tested for safety simply because it is not required by law.

    It is not surprising that unregulated use of these herbal preparations/extracts lead to side-effects.

    There is an urgency for government agencies to step-in and to introduce new rules vis-a-vis herbal preparation/extracts, so that they are brought closer to the rigors of more conventional drug development.

    Unfortunately, a section of the press has served to fuel the confusion by equating the effects of a herbal preparations/extracts of ephedra with the chemical ephedrine.

    Hobbs: Is ephedrine similar to methamphetamine in its effects? The press has tried equating the two calling ephedrine “legal speed” because it is used a precursor in the production of methamphetamine.

    Dulloo:  Again, the issue of ephedrine versus herbal ephedra is of utmost relevance. Again I refer to the above scientific proceedings which was organized to assess the safety and efficacy of ephedrine in the treatment of obesity (International Journal of Obesity, 1993 Feb, 17 Suppl 1:S1-S78).

    The scientific evidence does not support the anecdotal evidence which has been reported by some of the press.

    In one of the symposium papers entitled “The acute and chronic cardiovascular and behavioral effects of caffeine, aspirin and ephedrine”, the anecdotal evidence which has been reported by the press was not substantiated. This does not mean that ephedrine is safe. It only means that over the past 50 years that ephedrine has been utilized in Western medicine, and that there is no scientifically-based evidence for these claims [being made by the press] about ephedrine.

    As for herbal preparations/extract, this is an entirely different issue.

    It needs to be addressed in clinical trials.

    There are many pharmacologically active ingredients in the herb ephedra and indeed in most other herb extracts.

    Of particular concern is that the extraction procedures directed at concentrating a “desired ingredient” may also be concentrating potentially “undesirable” ingredients, and hence increases the risk for side-effects.

    Surely, the entire herbal product should enter clinical trial for safety tests in the form as it is being marketed.”

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