Experts are cautious about the claim of drinking tea in type 2 diabetes

The claim that drinking tea can protect people from developing type 2 diabetes has been cautioned by many experts ahead of the European Diabetes Research Association’s annual meeting.

It is argued that people who drink four or more cups of tea every day – especially green, oolong, or black tea – are 17% less likely to develop type 2 diabetes than those who don’t drink tea. Drinking fewer cups of tea per day has not been found to be of any benefit.

“Our results are exciting as they suggest that people can do something as simple as drinking four cups of tea a day to potentially reduce the risk of developing type 2 diabetes,” quotes Xiaying Li of Wuhan (China) University of Science and Technology. in the official EASD press release.

“It is possible that individual tea ingredients, such as polyphenols, can lower blood glucose levels, but enough of these bioactive compounds may be needed to be effective,” added Dr. Li.

“The words ‘suggest’ and ‘potentially’ are key here,” said Dr. Kevin McConway, PhD student retired professor of applied statistics at The Open University, said in a separate press release that sparked enthusiasm by Dr. Li.

“Drinking tea would only be useful to reduce the risk of diabetes if drinking tea reduces the risk, that is, if the risk is reduced if you drink tea, not if you don’t drink it – and this study simply cannot show if it does. or not, Dr. Conway emphasized.

Naveed Sattar, FMedSci FRCPath FRCPGlas FRSE, Professor of Metabolic Medicine at the University of Glasgow, was also cautiously critical. “There is no good trial evidence that the chemicals in tea prevent diabetes,” noted separately.

“So I suspect that it is more about making tea healthier (less calories) than many alternative drinks or tea drinkers who lead a healthier life overall.”

Dr. Sattar added that it could be that people who drink tea may also avoid drinking more harmful sugary drinks and have other health behaviors that may lead to a lower risk of developing type 2 diabetes.

Tea time?

Dr. Li will present the results of two analyzes on September 21 at the EASD meeting: the first is a large observational cohort study and the second is an updated systematic review and meta-analysis.

In a cohort study, Dr. Li and her co-authors collected data on more than 5,100 adults who participated in the long-term and ongoing China Health and Nutrition Survey (CHNS). Information on tea drinking behavior was taken from questionnaires that were completed at two time points – 1997 and 2009 – and determined whether people developed type 2 diabetes according to the criteria of the American Diabetes Association.

They found that nearly half, 45.8%, drink tea, and 10% of the population they studied had type 2 diabetes. However, no association was found between tea drinking and the development of type 2 diabetes, with a risk ratio comparing tea drinkers and non-drinkers teas that sit firmly at 1.02. Moreover, a sensitivity analysis that excluded participants who developed type 2 diabetes within the first 3 years of follow-up did not change the result.

Things were a bit different when Dr. Li and colleagues performed a meta-analysis that looked at data on over a million participants in 19 studies conducted in eight countries that were published by September 2021.

Here they discovered that there is a significant (P. <0.003) a linear relationship between tea consumption and type 2 diabetes, with the relative risk of developing type 2 diabetes reduced by 0.986 for each additional cup of tea consumed.

The HR for the development of type 2 diabetes in tea drinkers compared to non-tea drinkers was 1.00 for those who drank less than one cup a day, 0.96 for those who drank one or two cups, and 0.84 for those who drank less than one cup per day. who have drunk four or more cups.

“While more research is needed 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 in high doses (at least 4 cups a day),” said Dr. Li .

Perhaps “in our cohort study, we did not find a link between tea drinking and type 2 diabetes because we were not looking at higher tea consumption,” she added.

Storm in a cup

“This is large observational data. This is not a randomized, controlled trial, so there’s plenty of room for misunderstanding the data, ”warned Matt Sydes, M.Sc., professor of clinical research and methodology at MRC Clinical Trials Unit, University College London.

“Everyone drinks liquids. If there’s an effect here (and a big one, if), it may not be with the tea they drink, but with what they don’t drink. At the moment it is impossible to say. It seems unlikely that a large randomized controlled trial could be performed to disambiguate, ‘added Dr Sydes.

“Being just a summary of the conference, it’s hard to judge the quality of this research,” said Dr. Baptiste Leurent, a medical statistician also working at University College London. He noted that the cohort study was not only observational, but all other studies were included in the meta-analysis.

“Therefore, no cause-and-effect conclusions can be drawn. The association may simply be due to other factors, such as drinking more tea, leading a healthier lifestyle. in a meta-analysis, ‘said Dr Leurent.

“There is reason to be a bit skeptical at this point; we really need full details to properly evaluate this, ”said Jonathan Cook of the Center for Statistics in Medicine at the University of Oxford, England. “It’s an honest attempt to look at it, but not innovative, [using] fairly standard approach. “

Similar studies have shown a reduced risk associated with drinking coffee, noted Dr. Duane Mellor, a registered dietitian and senior lecturer at Aston University in Birmingham.

“An important message for home is that lifestyle is important in managing your risk of developing type 2 diabetes,” said Dr. Mellor.

“This includes a choice of low calorie drinks, mainly water, as well as unsweetened tea and coffee as selected drinks as part of a healthy lifestyle.”

The study was funded by the Young Talents Project of Hubei Provincial Health Commission, Science and Technology Research Key Project of Education Department of Hubei Province, Sanuo Diabetes Charity Foundation, and the Xiangyang Science and Technology Plan Project, all based in China. Dr. Li had no conflict of interest to disclose. Dr. McConway is a trustee and member of the Science Media Center’s advisory committee. Dr. Sattar has consulted with many diabetes and cardiovascular drug companies and has been involved in many attempts to approach lifestyle for the prevention and remission of diabetes. Dr. Sydes, Dr. Leurent, Dr. Cook, and Dr. Mellor have reported no conflicts of interest.

This story originally appeared on MDedge.com, part of the Medscape Professional Network.

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