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Nutritional Supplements #1: Green Tea
By:  Alicia Berthiaume   (2003/11/28)


Canadian skiers are still buzzing about Beckie Scott’s bittersweet Olympic medal, and as a result, we are gaining hope for a drug-free world of sport. But the debate about the ethics of supplementing (with vitamins, minerals or other) is still a foggy area for athletes. Without a little bit of understanding of the biochemistry behind the supplements, we put ourselves at risk on many levels. We may be taking something that is damaging to our health, we may be taking something in the wrong doses or we may be taking something illegal in competitive sport. It barely sounds worth it right? Don’t be discouraged thought, there are many incredible benefits to supplementing, if you know what to look for. So over the next season XC Ottawa will feature a panel of vitamin, minerals, herbal supplement and others that have been in the limelight recently. Hopefully with a bit of explanation, we’ll be able to understand what all the excitement is about! [Please check with your Doctor before starting use of any new supplement, natural’ or otherwise]



One popular herbal supplement in the media these days is green tea, or more specifically, the active catechin polyphenol components of green tea. Several types of tea (black, oolong, white) including green tea have been heralded for their powerful antioxidant properties thanks to these catechin polyphenols. Green tea however, boasts fat burning properties as well thanks to it’s unique polyphenol called epigallocatechin gallate (EGCG). Sound too goo to be true? Well it’s good and it’s true, so let’s examine how it works in order to understand why it works.


Our bodies maintain a core temperature of about 37oC through a combination of shivering and non-shivering thermogenesis. To increase fat metabolism, green tea acts on non-shivering thermogenesis, so we will focus on this type. As the name implies, with non-shivering thermogenesis heat is generated not by our muscles doing quick bursts of energy (shivering creating heat) but by some other method. The other method is a chemical pathway (via the sympathetic nervous system, SNS) triggered by our internal thermostat in the hypothalamus (in your brain), resulting in heat. The hypothalamus, in response to a drop in body temperature, releases noradrenaline, which prompts a cascade of enzyme production and activation, yielding heat.

Now, a bit of background: Mitochondria are little energy producing factories that are present in almost all cells of the body. They are what transform and harness the energy from food into the usable chemical bonds of ATP molecules. ATP molecules are what power our cells, muscles, even our brains. The chemical mechanism of non-shivering thermogenesis occurs in our brown fat cells, which contain many more mitochondria than most other types of cells.

Brown fat mitochondria are unique in that they are ‘leaky’. That is, when the hypothalamus releases noradrenaline and triggers thermogenesis, the energy transformation from food to ATP is left incomplete and the energy is leaked out. It sounds like a defect, but in fact the leak is purposeful. When the energy that began the transformation to ATP is leaked out of the mitochondria, it is dissipated as heat. Normally this heat would be considered wasted energy because it was not transformed into ATP to drive other processes in the body, but here the goal was to warm the body up, therefore heat is success. So, while there is no useful energy created (for moving or thinking) by burning these food calories, our bodies are warmed and our core body temperature is maintained.

Green tea can extend this calorie burning thermogenic effect by inhibiting the breakdown of the noradrenaline trigger. Enzymes that breakdown chemical messengers, such as noradrenaline, naturally exist in our nervous systems. They mediate the length and strength of triggered responses. In this case, if the noradrenaline is degraded more slowly due to the ECGC of green tea, then thermogenesis continues for a longer period, burning more calories.

Now this is all very small scale and green tea supplementation yields about a reasonable 4% increase in daily energy expenditure. However, this process favors fatty acids as fuel, therefore making it a suitable supplement for shedding excess fat. The reason this thermogenesis favors fat has to do with the role of noradrenaline in the ‘fight or flight’ response. One way nordrenaline prepares the body to act is by mobilizing large energy stores, namely fat. The proximity of the thermogenic mitochondria (inside fat cells) to the abundant resource of stored energy (fatty acids inside fat cell) made usable by noradrenaline, makes fat the right fuel choice.

It should also be noted that in contrast to other thermogenic weight loss supplements containing ephedra or caffeine, green tea has been shown to have no effect on heart rate or blood pressure. This difference in mechanism makes green tea much safer for anyone, especially athletes, to use.

So whether it be to fight flab or free radicals or simply to relax with a good book, brew up a pot of green tea and enjoy!

P.S. There are different methods used by different companies to measure the quantity of active ingredient in green tea extracts, so it is wise to talk to the naturopath or pharmacist before buying this supplement.

Interesting Reading. . .
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