Research has shown that green tea consumption can help overall health and there have been indications that green tea, particularly its catechins, can offer protective factors against obesity. But how?
When someone consumes foods with more starch than his or her body needs, the excess starch is converted to fat and is stored by the body. Thus a diet too high in carbohydrates can lead to unhealthy weight gain. Scientists at Poznan University of Medical Sciences in Poland believe that green tea might help block this conversion, reducing the digestion and absorption of starches.
The Poznan team, led by Klaudia Lochocka and Joanna Bajersk, conducted a study with 28 volunteers ranging in age from 19-28. They were asked to avoid particular high-starch foods for 5 days before the study and then fast 24 hours before the trial. A CO2 breath test was conducted. These breath tests can help measure the breakdown of carbohydrates and are not invasive like blood tests or other strategies.
Green tea was ground to a powder, steeped, filtered and extracted. The extract was then put into a starch wafer. The wafer contained the equivalent of several cups of green tea. Participants were then given a bowl of cornflakes and milk and a starch wafer that either contained the green tea extract or served as a placebo. The CO2 breath test was repeated following the consumption of the cornflakes and wafer at time intervals of 30, 60, 90, 120, 150, 180, 210 and 240 minutes. The study was repeated a week later with the extract group receiving the placebo and vice versa.
The results indicated that more than 78% of the participants who were given a wafer with high levels of green tea extract showed lower levels of glucose conversion and absorption. The effect of the green tea extract was very quick and persistent through the 240 minutes of testing.
It is important to recognize that the wafer was the catechin equivalent of several cups of green tea. It is not clear that the consumption of tea in its traditional form or in lesser quantities would have the same impact.
Results from the study (“Green tea extract decreases starch digestion and absorption from a test meal in humans: a randomized, placebo-controlled crossover study”) were recently published in Scientific Reports.