There’s no ‘tea’ in ‘diabetes’, and according to new research, a regular intake of the first can help prevent the risk of developing the latter.

New research presented at the 2022 European Association for the Study of Diabetes (EASD) Annual Meeting has looked at data from almost 20 different studies that, together, drew on data from more than one million adults. The research found a link between the drinking of tea and reduced incidence of type 2 diabetes — however, this effect was strongly dependent on the quantity of tea each participant drank regularly.

The findings come to complete our understanding of the relationship between tea drinking and type 2 diabetes in particular. Previously, the team explains, the consumption of tea has been linked to potential health benefits such as improved cardiovascular health and reduced risk of developing cancer.

A matter of quantitea

“It is possible that particular components in tea, such as polyphenols, may reduce blood glucose levels, but a sufficient amount of these bioactive compounds may be needed to be effective,” speculates Xiaying Li, lead author of the paper. “It may also explain why we did not find an association between tea drinking and type 2 diabetes in our cohort study, because we did not look at higher tea consumption.”

The study consisted of a two-part review of pre-existing research. The first stage was a cohort study that looked at data from over 5,000 adults who were followed for a 12-year period. Around half of the participants reported drinking tea but did not show any different rate of type 2 diabetes incidence between tea drinkers and non-drinkers by the end of the follow-up period.

The second part of the research explored whether the quantity of tea that each participant drank regularly could have an effect on type 2 diabetes outcomes. It pooled data from 19 studies regarding tea-drinking frequency, finding that the risk of developing type 2 diabetes did decline as the amount of tea a person was regularly drinking increased.

People who drank 1-3 cups of tea per day were 4% less likely to develop type 2 diabetes compared to non-drinkers. Those who drank 4 or more cups a day slashed their risk by 17%. This change was consistent across gender, geographical location, and the type of tea consumed (black tea, green tea, and oolong tea). As such, the team believes that some compound or compounds present in all types of tea may specifically reduce the risk of developing type 2 diabetes in regular tea drinkers.

That being said, there are some limitations to these findings. First, it is not yet peer-reviewed nor published in a scientific journal, meaning that the methodology and conclusions drawn in the study were not double-checked by other researchers. Secondly, the data it used was based on self-reported dietary questionnaires, which can be less reliable than directly-observed data and don’t track long-term food habits in detail. Finally, the data didn’t cover some factors that could influence the health outcomes of tea, such as whether participants drank theirs with or without milk or sugar.

It is possible, for example, for milk to increase the effects of tea in reducing the risk of developing type 2 diabetes. At the same time, some previous research has found that milk can actually decrease the insulin-enhancing activity of tea, which could completely counteract its ability to stave off diabetes. Other habits or psychological factors associated with tea-drinking could also have benefited the observed effect.

“While more research needs to be done to determine the exact dosage and mechanisms behind these observations, our findings suggest that drinking tea is beneficial in reducing the risk of type 2 diabetes, but only at high doses (at least 4 cups a day)”, concluded Li.

Despite the findings, the team underscores that their study was observational in nature and cannot, and should not be used, to prove that drinking tea alone reduces the risk of developing type 2 diabetes — but they do reliably show that tea can contribute.

The study “Drinking plenty of tea may reduce the risk of developing type 2 diabetes, finds study in over a million adults” have been presented at The European Association for the Study of Diabetes Annual Meeting.