Daily supplements of an extract of green tea may reduce levels of a protein linked to heart disease, says a new study from the US.
Obese people with metabolic syndrome experienced decreases in levels of amyloid alpha, said to be a risk factor for cardiovascular disease, after drinking green tea or taking green tea extracts, scientists from Oklahoma State University and the University of Oklahoma report in Nutrition.
The eight week study also supported the tolerability of both the beverage and the extracts, but the researchers note that the regime did not affect the various features of metabolic syndrome.
Metabolic syndrome (MetS) is a condition characterised by central obesity, hypertension, and disturbed glucose and insulin metabolism. The syndrome has been linked to increased risks of both type 2 diabetes and cardiovascular diseases.
“Thus, green tea may be included as part of a comprehensive strategy involving diet, exercise, and specific dietary supplementations aimed at reversing inflammation, endothelial dysfunction, and cardiovascular risk factors in subjects with metabolic syndrome,” wrote the researchers, led by Arpita Basu.
The study adds to an ever-growing body of science supporting the potential benefits of green tea and its constituents, most notably EGCG (epigallocatechin gallate). To date green tea has been linked to a reduced risk of Alzheimer's and certain cancers, improved cardiovascular and oral health, as well as benefits in weight management.
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).
Basu and her co-workers recruited 35 obese people with MetS to participate in their randomised controlled trial. The participants, who had an average age of 42.5, were randomly assigned to consume four cups of green tea, two capsules of green tea extracts, or four cups of water per day for eight weeks.
Both sources of green tea (Camellia sinensis) were decaffeinated, and provided an average daily dose of about 450 mg of EGCG.
At the end of the study, Basu and her co-workers did not observe any differences in the various features of MetS, such as biomarkers of inflammation. However, both green tea interventions reduced levels of amyloid alpha compared to the control group, said the researchers. Specifically, the green tea drink reduced amyloid alpha levels by 14.5 per cent, while the extract reduced levels by 24.6 per cent after eight weeks.
“To our knowledge, this is the first study investigating the effects of decaffeinated green tea supplementation on biomarkers of inflammation and features of metabolic syndrome in obese population in the US,” wrote the researchers.
“Our study results show that green tea beverage or extract supplementation selectively lowers plasma serum amyloid alpha versus the no treatment group,” they added.
The success has translated into a booming extract market, valued at a around $44m (€29.7m), according to recent report from Frost & Sullivan. The market is expected to grow by more than 13 per cent over the next seven years. Key players include DSM, Taiyo, and Tate & Lyle. Innovation in delivery has also seen companies like Maxx Performance release an encapsulated green tea extract for bakery applications.
Published online ahead of print, doi: 10.1016/j.nut.2010.01.015
“Green tea minimally affects biomarkers of inflammation in obese subjects with metabolic syndrome”
Authors: A. Basu, M. Du, K. Sanchez, M.J. Leyva, N.M. Betts, S. Blevins, M. Wu, C.E. Aston, T.J. Lyons