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.
