A new US study has shown that nutritional supplements containing a green tea extract may lower levels of a specific protein that has been linked to cardiovascular disease. Obese people (people whose weight is 30% higher than what is considered healthy for their height) diagnosed with metabolic syndrome showed lower circulating amounts of amyloid alpha after they drank green tea or took green tea extracts in supplement form. The study was done by scientists from the University of Oklahoma and Oklahoma State University, and was reported in the journal Nutrition.
The study took place over an eight-week period, and the green tea and extracts were well tolerated over that period. Researchers noted that neither the tea nor the vitamin supplements affected the features of the patients' metabolic syndrome. Metabolic syndrome is a cluster of conditions characterized by high blood pressure, obesity, and somewhat abnormal glucose and insulin function. It is linked to higher risk of type 2 diabetes and heart disease.
Lead researcher Arpita Basu reported that green tea may be a part of an overall strategy covering exercise, diet, and dietary supplementation used with the aim of reversing some of the risk conditions associated with metabolic syndrome, such as endothelial dysfunction, inflammation, and heart disease risk factors. The study also supported an increasing body of evidence showing possible benefits of green tea and some of the substances found in it. One of those substances, epigallocatechin gallate, or EGCG is the most notable green tea substance studied. It has been linked to lower risk of some types of cancer, Alzheimer's disease, heart disease, and even gum disease, and has shown that it might be beneficial for weight management.
Green tea is high in levels of water-extractable polyphenols. Black tea, which is green tea that has been fermented and oxidized, has lower levels. Oolong is semi-fermented, and has levels between those of black tea and green tea. The polyphenols found in green tea leaves are EGCG, epicatechin (EC), epicatechin gallate (ECG), and epigallocatechin (EGC). Some vitamin supplements and nutritional supplements contain these green tea extracts. In the study, 35 obese people with metabolic syndrome and an average age of 42.5 were assigned randomly to one of three groups: • a group that consumed 4 cups of green tea per day • one that consumed two green tea extract capsules per day • and another that consumed 4 cups of water per day (control group)
The green tea and nutritional supplements were decaffeinated and resulted in an average daily dose of EGCG of around 450 mg. When the eight weeks were up, the researchers didn't observe differences in the features that are found with metabolic syndrome, such as biological markers indicating inflammation. But both types of green tea interventions cut levels of amyloid alpha compared to the control group. Drinking green tea reduced amyloid alpha levels by 14.5%, and the extract reduced levels by 24.6% after eight weeks.
This is the first study investigating the effects of green tea or vitamin supplements containing green tea extracts on features of metabolic syndrome in obese people in the US. The results showed that green tea either consumed as a beverage or taken as nutritional supplement selectively lowered plasma amyloid alpha levels compared to those in the control group.