Green Tea
Green tea is one of the most commonly consumed beverages in the world! Coffee and water though probably run neck and neck with it. Many of us love the beverage (and/or take the extract) because of its potential thermogenic and weight loss properties.(1) What makes green tea so special are a family of polyphenols (catechins) and flavonols which have potent antioxidant activity. Tannins, which are large polyphenol molecules, form the bulk of the active compounds in green tea, with catechins comprising nearly 90%. Perhaps the most ‘popular’ of these catechins is ECGC or epigallocatechin gallate. EGCG is probably the strongest of the catechins and makes up about 10-50% of the total catechin content. Some have suggested that EGCG has antioxidant activity that may be 100 times stronger than vitamins C and E. Green tea has been shown to improve exercise capacity perhaps by an increased utilization of fatty acids as a source of energy by muscle during exercise.(2) Interestingly, there is intriguing data to show that green tea can play a role in helping weight loss or perhaps improving body composition. For instance, a study published in the American Journal of Clinical Nutrition investigated whether a green tea extract, by virtue of its high content of caffeine and catechin polyphenols, could increase 24-hour energy expenditure (EE) and fat oxidation in humans. They measured twenty-four-hour EE, the respiratory quotient (RQ which is a measure of the type of fuel your body uses [carbs vs fats] ), and the urinary excretion of nitrogen and catecholamines (adrenaline hormones) were measured in 10 healthy men. On three different occasions, subjects consumed the following: green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), and placebo, which they ingested at breakfast, lunch, and dinner.
What did they discover? Relative to placebo, treatment with the green tea extract resulted in a significant increase in 24-h EE (4%) and a significant decrease in 24-h RQ without any change in urinary nitrogen. Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on EE and RQ nor on urinary nitrogen or catecholamines. They concluded that green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine alone. This study supports the notion that green tea extract may play a role in the control of body composition via enhanced thermogenesis, fat oxidation, or both.(3). Now you might be thinking that a 4% increase in calorie burning isn’t much. But if you look at the ‘theoretical’ implications, imagine if you typically burn 2000 calories a day (and consume the same) and are body weight stable. Now imagine if you burn 4% more calories. That would be equal to 80 calories per day. Assuming you carried out this strategy for 6 months, you could perhaps burn an additional 14,400 calories or the equivalent of 4 plus pounds. Over the long term this is significant.
Other studies have shown interesting results. For instance, another study assessed the body fat levels of human subjects taking a health supplement containing 0.4 mg capsaicin, 625 mg green tea extract (125 mg catechins and 50 mg caffeine) and 800 mg essence of chicken (CGTE). Now don’t ask me what ‘essence of chicken’ is. I’m merely here to report the study. Subjects were advised to maintain their regular dietary habits and routine physical activity throughout study duration. After 2 wk of supplementation with CGTE, the mean body fat percentage of males and female subjects was significantly less than at the start. Moreover, resting energy expenditure (REE) of the subjects taking the test samples were significantly increased in groups supplemented with CGTE, compared to placebo group. According to the study authors, the combined thermogenic effect of capsaicin, green tea extract and essence of chicken could translate to a positive clinical effect by reducing body fat.(4)
Beyond the potential improvements in body fat or composition, green tea may also have performance enhancing benefits as well as potent health-promoting properties. Scientists investigated the effects of green tea extract (GTE) on endurance capacity, energy metabolism, and fat oxidation in mice over a 10-wk period. Swimming times to exhaustion for mice fed 0.2-0.5% (wt/wt) GTE were prolonged by 8-24%. The effects were dose dependent (meaning the more they took, the better the mice performed) and accompanied by lower respiratory quotients and higher rates of fat oxidation. Therefore, GTE may improve endurance capacity and increase fat oxidation.(2) What about health? In fact, the data here are as robust as a Pam Anderson’s breasts. A double-blind, randomized, placebo-controlled trial of 240 men and women 18 years or older on a low-fat diet with mild to moderate hypercholesterolemia were randomly assigned to receive a daily capsule containing theaflavin-enriched green tea extract (375 mg) or placebo for 12 weeks. After 12 weeks, the average changes from baseline in total cholesterol, LDL-C, HDL-C, and triglyceride levels were -11.3%, -16.4%, 2.3%, and 2.6%, respectively, in the tea extract group. The mean levels of total cholesterol, LDL-C, HDL-C, and triglycerides did not change significantly in the placebo group. No significant adverse events were observed. So not only does green tea confer thermogenic and perhaps ergogenic properties, it is pretty damn good for your health! (5)
How much to take?
If you drink green tea regularly, keep doing it. It’s good for
you! However, if you take green tea supplements, a commonly suggested
dosage is 125-500mg/day. Many supplements that contain green tea also
contain extra caffeine for that thermogenic boost. Perhaps consuming
these types of supplements pre-workout is a great strategy for enhancing
exercise performance and ultimately improving body composition.
References
1. Diepvens K, Westerterp KR, Westerterp-Plantenga MS. Obesity and thermogenesis
related to the consumption of caffeine, ephedrine, capsaicin, and green
tea. Am J Physiol Regul Integr Comp Physiol 2007;292:R77-85.
2. Murase T, Haramizu S, Shimotoyodome A, Nagasawa A, Tokimitsu I. Green
tea extract improves endurance capacity and increases muscle lipid oxidation
in mice. Am J Physiol Regul Integr Comp Physiol 2005;288:R708-15.
3. 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;70:1040-5.
4. Tsi D, Nah AK, Kiso Y, Moritani T, Ono H. Clinical study on the combined
effect of capsaicin, green tea extract and essence of chicken on body
fat content in human subjects. J Nutr Sci Vitaminol (Tokyo) 2003;49:437-41.
5. Maron DJ, Lu GP, Cai NS, et al. Cholesterol-lowering effect of a
theaflavin-enriched green tea extract: a randomized controlled trial.
Arch Intern Med 2003;163:1448-53.