It’s no secret I’m a lover of tea, green tea in particular.
I’m sure all my fellow tea lovers out there can relate to the relaxing nature of sitting down to a nice cup of tea. This calming effect of tea can be attributed to a special amino acid known as L-theanine, shown to promote relaxation (Juneja et al 1999). In fact, L-theanine works synergistically alongside the small amount of caffeine found in tea to also improve concentration and cognition.
Unlike coffee, where many people find their concentration peaks within a few minutes, then quickly drops back down again (much like a ‘sugar high’), tea promotes a stable improvement in concentration and brain function without the sudden drop. Although students often rely on multiple cups of coffee to get them through study and exams, I often recommend a cup of tea as the beverage of choice about half an hour before sitting an exam.
Bioactive Compounds and Fat Oxidation
Tea, whether it be black, green or herbal all contain antioxidants and other bioactive compounds such as catechins and flavonoids. However, green tea in particular contains a higher level of an especially potent catechin known as epigallocatechin gallate (EGCG). It also has other vitamins and minerals which increase its antioxidant properties (Cabrera et al 2006).
Many studies investigating the benefits of green tea have used green tea extract instead of regular cups of green tea to measure the effects of a specific dosage of EGCG. One such study (Dulloo et al 1999) showed increased fat oxidation (attributed to green tea’s thermogenic properties) at doses of 90mg EGCG per day), supported by another study (Venables et al 2008) demonstrating a 17% increase in fat oxidation among participants taking green tea extract. Researchers found that green tea also improved the insulin sensitivity and glucose tolerance of the study participants, indicating that green tea may also help prevent the development of Type 2 Diabetes.
Heart Disease and Cancer
Several epidemiological studies have shown that regular green tea drinkers have a lower risk of cardiovascular disease and certain cancers.
Studies have shown lower cardiovascular disease mortality rates among green tea drinkers (Kuriyama 2008) and a 22% decrease in the risk of breast cancer among those with the highest intake of green tea (Sun et al 2006). One study has also found green tea drinkers to have a 57% lower risk of developing colorectal cancer than those who do not drink green tea (Yang et al 2007).
Furthermore, these benefits appear to occur in a dose-dependent manner (that is, the more green tea you drink, the better) with those drinking 5 of green tea per day having a 48% decrease in the risk of advanced prostate cancer compared with those who drink 1 or fewer cups per day (Kurahashi et al 2008).
For those of you wishing to cut down of your caffeine intake, green tea makes an excellent substitute for coffee. Try replacing just one cup of coffee each day with a cup of green tea instead, and aim for 3-4 cups per day for optimal benefits.
It goes without saying that tea is much easier to consume during the cooler months of the year, but stay tuned for a tasty recipe featuring green tea that is suitable for the summer season ahead.
Cabrera et al (2006), ‘Beneficial effects of green tea – a review’, Journal of the American College of Nutrition, 25(2): 79-99.
Dulloo et al (1999), ‘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, 70(6): 1040-1045.
Juneja et al (1999), ‘L-theanine – a unique amino acid of green tea and its relaxation effect in humans’, Trends in Food Science & Technology, 10(6): 199-204.
Kurahashi et al (2008), ‘Green Tea Consumption and Prostate Cancer Risk in Japanese Men: A Prospective Study’, American Journal of Epidemiology, 167(1): 71-77.
Kuriyama (2008), ‘The Relation between Green Tea Consumption and Cardiovascular Disease as Evidenced by Epidemiological Studies’, The Journal of Nutrition, 138(8): 1548S-1553S.
Sun et al (2006), ‘Green tea, black tea and breast cancer risk: a meta-analysis of epidemiological studies’, Carcinogenesis, 27(7): 1310-1315.
Venables et al (2008), ‘Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans’, American Journal of Clinical Nutrition, 87(3): 778-784.
Yang et al (2007), ‘Prospective cohort study of green tea consumption and colorectal cancer risk in women’, Cancer Epidemiology Biomarkers and Prevention, 16(6): 1219-1223.