Special edition: authentic tea tastes

What do scientists say about tea? Black tea and blood pressure; green tea and MRIs

By Rachel Arthur contact

- Last updated on GMT

What's the potential of green tea - and other teas?
What's the potential of green tea - and other teas?
Green tea could improve the quality of MRI scans, while black tea may decrease blood pressure, suggest scientists.

Green tea could help produce better MRIs

Green tea could improve the image quality of MRIs, report scientists in the journal ACS Applied Materials & Interfaces.​ 

MRIs (magnetic resonance imaging) is used by doctors to examine almost any part of the body, from the brain and spinal chord to internal organs such as the liver. 

Sanjay Mathur and fellow researchers coated iron-oxide nano particles with catechins (compounds from green tea). They administered these to mice with cancer. MRIs showed that these imaging agents gathered in tumour cells and demonstrated a strong contrast from non-tumour cells. 

Green (tea) is for go!

Green tea extract supplements could improve metabolic efficiency and economy​ - thus boosting performance in recreationally active men, according to the Journal of the International Society of Sports Nutrition​. 

The group of participants (14 active men averaging 21 years old) cycled for one hour, three times a week - over a study period of four weeks. 

Men who received a green tea extract had fat oxidation rates increase by almost 25%, while there were no changes observed in the placebo group. Meanwhile, the green tea group also saw an improvement in performance, covering a longer cycling distance by week four. 

Black tea and blood pressure

Drinking two cups of black tea a day has been associated with improvements in arterial stiffness and decreases in systolic and diastolic blood pressure, according to the journal Nutrients.

The study from Unilever R&D​ took 19 people with elevated blood pressure. These were randomly assigned black tea (with a flavonoid dose of 129 milligrams per serve) or placebo over the course of an eight day period. Tea was drunk without milk or sugar. 

Flavonoids have been shown to have beneficial effects on the cardiovascular system, observe the researchers behind the study. 

Green tea polyphenol targets cancer cells

Epigallocatechin-3-gallate (EGCG) may be able to trigger a process in mitochondria that leads to cell death in cancer cells - but leaves normal cells alone.

Earlier studies had shown EGCG (a polyphenol found in green tea) has an ability to kill oral cancer cells without affecting normal cells. In a study published in Molecular Nutrition and Food Research, ​Penn State food scientists showed EGCG may set off a cycle which eventually causes the cell to undergo programmed cell death. Meanwhile, normal cells increased their protective capabilities under the effect of EGCG, researchers suggest. 

Researcher Joshua Lambert suggested that, if used in anti-cancer treatments, green tea would not have the same side effects as chemotherapy drugs.

Sources:

ACS Applied Materials & Interfaces,​ 2015; DOI: 10.1021/am508404t​ 

“Enhanced In Vitro and In Vivo Cellular Imaging with Green Tea Coated Water-Soluble Iron Oxide Nanocrystals.”

L. Xiao, M. Mertens, L. Wortmann, S. Kremer, M. Valldor, T. Lammers, F. Kiessling, S. Mathur.

Journal of the International Society of Sports Nutrition,​ 2015, 12:1, doi:10.1186/s12970-014-0062-7

“The effect of a decaffeinated green tea extract formula on fat oxidation, body composition and exercise performance”
J.D. Roberts, M.G. Roberts, M.D. Tarpey, et al. 

Nutrients,​ 2015, Volume 7, Number 2, Pages 1037-1051, doi:10.3390/nu7021037

“Black Tea Lowers Blood Pressure and Wave Reflections in Fasted and Postprandial Conditions in Hypertensive Patients: A Randomised Study”

D. Grassi, R. Draijer, G. Desideri, T. Mulder, C. Ferri

Molecular Nutrition & Food Research,​ 2014, DOI: 10.1002/mnfr.201400485

“Differential prooxidative effects of the green tea polyphenol, (-)-epigallocatechin-3-gallate, in normal and oral cancer cells are related to differences in sirtuin 3 signaling.”

L. Tao, J. Park, J. D. Lambert.

Related topics: R&D

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