The cholesterol finding comes from an analysis of 14 randomized controlled trials involving a total of 1,136 participants and was published in the American Journal of Clinical Nutrition in 2011. The review was conducted by researchers from the Key Laboratory for Clinical Cardiovascular Genetics, the Sino-German Laboratory for Molecular Medicine, the Cardiovascular Institute, FuWai Hospital and Peking Union Medical College.
In all 14 studies, participants were divided into a placebo group and a group that drank either green tea or a green tea extract for between three weeks and three months. Overall, the researchers found that higher levels of green tea (or extract) consumption were associated with significantly lower levels of total cholesterol and LDL ("bad") cholesterol. No change was seen in the levels of HDL ("good") cholesterol.
Green tea is high in antioxidants, which protect cells from the damage and inflammation that lead to many chronic diseases, including heart disease. One of the antioxidant families found in green tea, known as the catechins, appears to decrease the gut's absorption of cholesterol.
These findings are particularly significant because although green tea consumption has strongly been linked to lower rates of heart disease, the mechanisms by which this protection functions have been unclear.
Because the observed cholesterol decrease in the studies was small, heart disease prevention specialist Nathan Wong of the University of California, Irvine cautioned against relying solely on green tea if you have dangerously high cholesterol. But green tea "could be a useful component of a heart-healthy diet," he said.
Green tea also reduces disabilityHeart protection it is just one of the many health benefits that researchers have linked to green tea. For example, a 2012 study published in the American Journal of Clinical Nutrition found that people who drink at least five cups of green tea per day stay significantly more agile and independent as they age, with a lower risk of disability and frailty.
The study, conducted by researchers at the Tohoku University Graduate School of Medicine, followed almost 14,000 people over the age of 64 for three years. They found that approximately seven percent of participants who drank five or more cups of green tea daily became functionally disabled in that time, compared with 13 percent of those who drank fewer than one cup per day.
Functional disability was defined as having trouble with everyday tasks, such as bathing or getting dressed.
People who drank more green tea were also more likely to have healthier diets, higher education, lower rates of smoking, more robust social networks, and overall better health. However, even when the researchers adjusted for potential interference from these factors, green tea consumption was still strongly correlated with lower disability risk.
"Green tea consumption is significantly associated with a lower risk of incident functional disability, even after adjustment for possible confounding factors," the researchers wrote.