DEFINITIVE GUIDE TO GREEN TEA AT A GLANCE
♦ GREEN TEA can help cut the risk of cancer
♦ GREEN TEA can lower blood pressure – and hence the risk of heart attack and stroke
♦ GREEN TEA can help reduce LDL (the dangerous form of) cholesterol and increase HDL – the beneficial form
♦ GREEN TEA can help reduce anxiety
Does clinical evidence support green tea’s image as an exceptionally healthy drink – and indeed as a supplement?
It does. The benefits include a reduced risk of cancer, lower blood pressure – thereby reducing the risk of heart disease and stroke – and possibly improved mental function and increased metabolism.
The most comprehensive clinical review of the benefits of green tea in recent years starts as follows:
“The health benefits of consuming green tea, including the prevention of cancer and cardiovascular diseases, the anti-inflammatory, anti-arthritic, anti-bacterial, anti-oxidative, anti-viral, neuroprotective, and cholesterol-lowering effects of green tea and isolated green tea constituents (ie extracts) are under investigation.”
That’s quite a roll call of potential health benefits.
It continues:
“Green tea consumption has been linked to the prevention of many types of cancer, including lung, colon, (o)esophagus, mouth, stomach, small intestine, kidney, pancreas, and mammary glands. Several epidemiological studies and clinical trials showed that green tea may reduce the risk of many chronic diseases.
“This beneficial effect has been attributed to the presence of high amounts of polyphenols, which are potent antioxidants. In particular, green tea may lower blood pressure and thus reduce the risk of stroke and coronary heart disease.”
The micronutrients in Green Tea
The key plant micronutrient accounting for green tea’s health benefits is known as EGCG, a type of catechin polyphenol called epigallocatechin-3-gallate. It is a very powerful anti-inflammatory and anti-oxidant, protecting cells and DNA against free radical damage which is at the heart of ageing, heart disease and some cancers.
A 2018 study found:
“EGCG was found to exhibit a wide range of therapeutic properties including anti-atherosclerosis, anti-cardiac hypertrophy, anti-myocardial infarction, anti-diabetes, anti-inflammatory and anti-oxidant.”
For highest EGCG levels, choose standardised quality
The best green tea supplements are standardised – meaning that they contain high and defined levels of EGCG. But many cheap supplements are not standardised.
Matcha green tea as a drink is the best – containing up to 80 times the EGCG levels of ordinary green tea.
Green tea and reduced cancer risk
We’ve already seen that green tea has both anti-inflammatory and anti-oxidant effects.
Oxidative damage to DNA is an initiator of cancer. Inflammation also actually causes some cancers and creates an internal environment where other cancers are more likely to spread.
Prostate cancer
The American Association of Cancer Research have concluded that:
“The polyphenols present in green tea help prevent the spread of prostate cancer by targeting molecular pathways that shut down the proliferation and spread of tumour cells, as well as inhibiting the growth of tumour nurturing blood vessels”.
(Soy isoflavones also discourage the growth of the blood vessels that feed tumours).
Breast cancer
But it’s not only the reduction in prostate cancer that means green tea and green tea supplements should feature in your overall health programme. Breastcancer.org advise that:
“In laboratory and animal studies, EGCG has been shown to limit the growth of breast cancer cells and other types of cancer cells. One study of Asian-American women found that those who drank more green tea were less likely to develop breast cancer.”
There is even evidence that EGCG, in addition to acting an anti-tumour agent, also helps modulate tumour cell response during chemotherapy.
Green tea and improved heart health
An analysis in the British Journal of Nutrition in 2014 of 25 randomised controlled trials concluded that long-term green tea intake significantly improved blood pressure.
“After 12 weeks of drinking tea, blood pressure was lower by 2.6 mmHg systolic and 2.2 mmHg diastolic.
“The present findings suggest that long-term (over 12 weeks) ingestion of tea could result in a significant reduction in systolic and diastolic BP.”
Time Magazine concluded that:
“Reducing systolic blood pressure by 2.6 mmHg ‘would be expected to reduce stroke risk by 8 percent, coronary artery disease mortality by 5 percent and all-cause mortality by 4 percent at a population level…”
It appears that these heart health benefits are largely due to the ability of green tea to relax blood vessels called endothelial cells, which line the body’s circulatory system. This effect is rapid – occurring in as little as 30 minutes from consumption. This also has the effect of helping protect against blood clots.
Green tea and improved brain function
Green tea also includes both caffeine and an amino acid called L-theanine. In turn, L-theanine increases the activity of a neurotransmitter called GABA. The result of this sequence is to increase levels of dopamine in the brain which reduces anxiety, whilst simultaneously increasing alertness.
Green tea and weight control – maybe
Results of a study reported in the American Journal of Clinical Nutrition showed that 90mg of a green tea supplement taken 3 times a day appears to exert a thermogenic effect – ie. it increases metabolism and energy expenditure.
So green tea could be helpful as part of a weight control programme, but it is unlikely to work on its own unless there is an accompanying reduction in calories.
Indeed, a subsequent double-blind trial reported in Clinical Nutrition showed no real effect on body weight – BUT it did confirm that the group taking green tea supplements had a:
- significant reduction in LDL-cholesterol and triglyceride
- marked increase in the level of HDL-cholesterol (the ‘good cholesterol), and adiponectin. (Adiponectin is a hormone that helps regulate glucose levels.)
Conclusions
Green tea contains an unusually wide array of vitamins and minerals in addition to its catechins – including vitamins A, C, D, E, B5 and K, and minerals such as manganese, zinc, chromium and selenium.
You may like to squeeze a little lemon juice into your cup of green tea – or buy green-tea-with-lemon. Researchers have shown that vitamin C may increase the bioavailability of catechins by more than 500%!
Green tea supplements
Once again, however, neither green tea nor green tea supplements on their own are the only or ideal health protective nutrients. NutriShield Premium is a daily comprehensive supplement containing 43 nutrients including 150mg of standardised polyphenols with 75mg of EGCG and 37.5mg of other catechins, designed by Dr Paul Clayton, former Chair of the Forum on Food and Health at the Royal Society of Medicine.
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REFERENCES
Beneficial effects of green tea: A literature review Sabu M Chacko, Chin Med. 2010; 5: 13. Published online 2010 Apr 6. doi: 1186/1749-8546-5-13
Molecular understanding of Epigallocatechin gallate (EGCG) in cardiovascular and metabolic diseases. Eng QY, Thanikachalam PV, Ramamurthy S. J Ethnopharmacol.2018 Jan 10;210:296-310. doi: 10.1016/j.jep.2017.08.035. Epub 2017 Aug 31
Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Abdul G Dulloo. The American Journal of Clinical Nutrition, Volume 70, Issue 6, 1 December 1999
Effect of green tea extract on obese women: A randomized, double-blind, placebo-controlled clinical trial. Chung-Hua et al: Clinical Nutrition; Volume 27, Issue 3, June 2008, Pages 363-370
Green tea catechin, epigallocatechin-3-gallate (EGCG): mechanisms, perspectives and clinical applications. Singh BN, Shankar S, Srivastava RK. Biochem Pharmacol. 2011 Dec 15;82(12):1807-21. doi: 10.1016/j.bcp.2011.07.093. Epub 2011 Jul 30.
Effects of tea intake on blood pressure: a meta-analysis of randomised controlled trials. Gang Liu. British Journal of Nutrition; Volume 112, 14 October 2014 , pp. 1043-1054
Benefits Of Green Tea In Reducing An Important Risk Factor For Heart Disease; European Society of Cardiology
L-theanine, a natural constituent in tea, and its effect on mental state. Nobre AC, Rao A, Owen GN. Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-8.