There has never been a better time to go green, according to a team of US food scientists who say that green tea may slow weight gain and has the potential to play an integral role in the battle against obesity.
Publishing their findings in online journal Obesity, researchers from Pennsylvania State University found that a control group of obese mice who were fed Epigallocatechin-3-gallate (EGCG) – a compound found in most green teas – in addition to a high-fat diet gained weight 44 per cent slower than their counterparts who were fed the same diet without the compound.
“Our work suggests that EGCG inhibits an enzyme called pancreatic lipase (PL), which is secreted into the intestine when you eat and is the most important enzyme for the digestion of dietary fat,” explains study author Joshua Lambert, assistant professor of food science at Pennsylvania State University. “EGCG, in the test tube, inhibits this enzyme at relatively low concentrations. Definitely concentrations that are achieved in the intestine when you drink a cup or two of tea.”
The study also proposes that it could provide a cheap alternative to clinical weight-loss drugs, proving to be as effective while lacking the sometimes debilitating side effects. Though Lambert advocates drinking tea over the use of pills containing pure compounds, as human case studies have shown links between consumption of high doses of green tea-based dietary supplements and liver toxicity.
“We think this mechanism is relevant in animals, and probably in people, because mice treated with EGCG have elevated faecal fat content,” he adds. “To us, this suggests that the fat is not being digested, and is instead passing through the intestine and into the faeces. One pertinent point is the PL is the target for Orlistat [Australian trade name Xenical], a clinically used drug for weight loss.”
The findings support earlier research undertaken at the Department of Human Biology, Nutrition and Toxicology Research Institute at Maastricht University in the Netherlands. Scientists there conducted a meta-analysis of multiple studies on the effects of green tea on weight loss and weight maintenance in humans and concluded that its consumption “significantly decreased body weight and significantly maintained body weight” after a period of weight loss.
“It has only been scientifically evaluated in the past 11 years, and it is thought that the combination of EGCG and caffeine are responsible for the weight loss,” says Teresa Mitchell-Paterson, Head of Academic Studies (Natural Therapies) at the Australasian College of Natural Therapies. “However the consumption of caffeine alone does not give the same fat-loss benefit.”
Extrapolating from the mice study, Lambert says a human being would have to drink 10 cups of green tea per day to ingest a dose of EGCG equivalent to that given to the mice, but further research is required to establish a more effective dose, and what the magnitude of the effect actually is.
It’s advised that those with heart conditions or major cardiovascular problems strictly limit their intake of caffeine, while pregnant and breast-feeding women should drink no more than one-to-two cups of green tea per day, since it can cause an increase in heart rhythm. Given these concerns, Mitchell-Paterson says a more pragmatic approach might be suitable for everyone.
“Studies suggest that approximately 150mgs of green tea is needed to gain a therapeutic effect, which is approximately three-to-four cups daily,” she says. “Dosage must be kept to three-to-four cups per day due to the caffeine content of green tea, [and] there is no data regarding toxicity of long term use.”