A flavonoid found in green tea helped reduce spikes in blood glucose levels by 50% in mice fed a starchy diet, according to a new study published online in the journal Molecular Nutrition and Food Research. The findings suggest epigallocatechin-3-gallate (EGCG) may help humans control the typical blood sugar increases brought on when they eat starchy foods, like breads and bagels.
For the study, Penn State food scientists separated mice into several groups based on body weight. After a fasting period, the mice were given common corn starch, maltose or sucrose. One group of mice received EGCG along with the feed, while a control group was not fed the compound. The researchers then tested the blood sugar levels of both groups. The mice fed a compound of EGCG and corn starch had a significant reduction in increase in their blood sugar levels compared to mice that were not fed the compound. EGCG was most effective when the compound was fed to the mice simultaneously with corn starch.
"If what you are eating with your tea has starch in it then you might see that beneficial effect," the researchers said. "So, for example, if you have green tea with your bagel for breakfast, it may reduce the spike in blood glucose levels that you would normally get from that food."
The EGCG had no significant effect on blood sugar spikes in mice that were fed glucose or maltose. The researchers said the reason blood sugar spikes are reduced when the mice ate starch, but not these sugars, may be related to the way the body converts starch into sugar. An enzyme called alpha-amylase that is produced in both the mouth and by the pancreas helps break down starch into maltose and glucose. EGCG may inhibit the enzymes ability to break down the starch, the researchers indicated, since they also found that EGCG reduced the activity of alpha amylase in the pancreas by 34%. If the mechanism holds in humans, this may mean that people who want to limit the blood sugar spike should skip adding sugar to their cup of green tea.
"That may mean that if you add sugar into your green tea, that might negate the effect that the green tea will have on limiting the rise in blood glucose level," they said, adding that the green tea and starch would need to be consumed simultaneously. For example, drinking a cup of tea well after eating a piece of toast would probably not change the blood sugar spike.
