GREEN TEA

We have all heard it. Green tea is good for you. But have you ever wondered what this simple tea actually does once consumed? How does it work? And what does this mean for those of us who drink it?

Let me break green tea down into three important components: caffeine, theanine and catechins. Most of us have a reasonable idea of the implications of caffeine on the body- it is a stimulant which gives us energy and increases metabolism (perhaps a topic for another post). However, one component that plays a huge role in the health benefits of green tea, and that is less well known is catechins.

Firstly, catechins act as antioxidants in the body. When the body undergoes a number of different processes, for instance cigarette smoking or even DNA strand breaking, it produces reactive oxygen “radicals” as bio-products. These radicals cause damage to the cells, and antioxidants prevent this damage by acting as scavengers of these radicals. Catechins also modulate many risk factors that contribute to pertinent medical issues such as lowering blood levels of leptin (fat), and causing a 20% increase in red blood cell haemoglobin. Research is still underway, but so far there is significant reason to investigate the impact of green tea on decreasing the risk of heart disease, allergies, immune diseases and even a variety of cancers. It certainly seems worth the cup!

And when you thought this little cup of magic couldn’t get any better, it was scientifically proven to play a role in weight and body composition.  A randomised control trial in The American Journal of Clinical Nutrition compared the effects of green tea, caffeine and a placebo which were ingested at breakfast, lunch and dinner on three separate occasions (Dulloo et al., 1999). The green tea (compared to the placebo) was found to significantly increase energy expenditure over a 24 hour period by 4%.  It was also found the significantly decrease respiratory quotient from 0.88 to 0.85. Respiratory quotient is a measure of metabolism as it represents the amount of carbon dioxide eliminated versus the amount of oxygen consumed in the body. Lower levels indicate that the body is burning fat. Overall, it was concluded that green tea plays a role in fat oxidation and body composition, and that these effects are not the result of caffeine alone, but of properties specific to green tea.

Therefore, green tea contains properties that are extremely beneficial to our health, including reducing the risk of many common diseases, as well as enhancing our metabolism and energy levels. So why not add a little green to your day?

References:

Dulloo, Duret, Rohrer, Girardier, Mensi, Fathi, Chantre, & Vandermander. (1999). Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. The American Journal of Clinical Nutrition, 70, 1040-1045.

Liao, Kao, & Hilpakka. (2001). Green tea: Biochemical and biological basis for health benefits. Vitamins & Hormones, 62, 1-94.