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Green tea extract may lower blood pressure: study

By Stephen Daniells , 30-Oct-2008

Daily supplements of extracts from green tea (Camellia sinensis) may reduce blood pressure, cholesterol and markers of oxidative stress, and all within three weeks, says a new study.

Reductions of systolic and diastolic blood pressures of 5 and 4 mmHg, respectively, were observed following daily supplements of green tea extracts, while total cholesterol levels were reduced by 10 mg/dL, according to findings of a randomised, double-blind, placebo-controlled, parallel study.

The study adds to an ever growing body of science reporting the potential health benefits of green tea and its extracts, which already range from reduced risks of cardiovascular disease, Alzheimer’s, and certain cancers.

Researchers from the University of Florida, Brigham and Women’s Hospital and Harvard Medical School, and the Nutritional Science Research Institute, Boston, report their findings in Nutrition.

Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. Oolong tea is semi-fermented tea and is somewhere between green and black tea.

The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC).

Study details

Meri Nantz and co-workers recruited 52 healthy men and 72 healthy women with an average age of 29 and randomly assigned them to receive daily supplements of green tea extract (Cardio Guard, containing 100 mg of L-theanine (Suntheanine, Taiyo International) and 200 mg of a decaffeinated catechin green tea extract (Sunphenon 90DCF, Taiyo International)) or placebo for three weeks.

At the end of the supplementation period the researchers found that total and LDL cholesterol levels had decreased by 10 and 9 mg/dL, respectively.

In addition to the blood pressure improvements, improvements in malondialdehyde (a marker of oxidative stress) and amyloid-alpha (a marker of chronic inflammation) were also recorded. Specifically, 12 and 42 per cent reductions, respectively, were observed.

Camellia sinensis compounds may be an option for people who have mild to moderate high BP, elevated LDL cholesterol, elevated markers of inflammation, or a combination of these three CVD risk factors,” wrote the researchers.

“It may be helpful for individuals whose health care providers suggest a trial of diet and exercise before resorting to prescription medication,” they concluded.

High blood pressure (hypertension),defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg, is a major risk factor for cardiovascular disease (CVD) - a disease that causes almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.

Source: NutritionPublished online ahead of print, 9 October 2008, doi: 10.1016/j.nut.2008.07.018“Standardized capsule of Camellia sinensis lowers cardiovascular risk factors in a randomized, double-blind, placebo-controlled study”Authors: M.P. Nantz, C.A. Rowe, J.F. Bukowski, S.S. Percival