Drinking plenty of tea may reduce the risk of d... - Thyroid UK

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Drinking plenty of tea may reduce the risk of developing type 2 diabetes, finds study in over a million adults

helvella profile image
helvellaAdministrator
36 Replies

Many of us might see variations on this story across the media.

I have many issues with it:

It is not yet a peer reviewed and published paper. It appears to have been selected for headline grabbing potential.

In what I have been able to read, the effect of sugar (and other sweeteners) appears to be ignored. Doesn't that even suggest itself as a factor in the context of diabetes?

The impact on tea sales might be an important factor!

At the same time, it just might be an interesting, even important, observation/report. And given the various links between diabetes and thyroid issues, it could at least be of slight interest.

Drinking plenty of tea may reduce the risk of developing type 2 diabetes, finds study in over a million adults

Four or more cups of black, green, or oolong tea every day linked to 17% lower risk of developing type 2 diabetes

Reports and Proceedings

Diabetologia

A systematic review and meta-analysis of 19 cohort studies involving more than 1 million adults from eight countries finds that moderate consumption of black, green or Oolong tea is linked to a lower risk of developing type 2 diabetes.

The findings, being presented at this year’s European Association for the Study of Diabetes (EASD) Annual Meeting in Stockholm, Sweden (19-23 Sept), suggest that drinking at least four cups of tea a day is associated with a 17% lower risk of T2D over an average period of 10 years.

“Our results are exciting because they suggest that people can do something as simple as drinking four cups of tea a day to potentially lessen their risk of developing type 2 diabetes”, says lead author Xiaying Li from Wuhan University of Science and Technology in China.

While it’s long been known that regularly drinking tea may be beneficial for health because of the various antioxidant, anti-inflammatory and anticarcinogenic compounds tea contains, less clear has been the relationship between tea drinking and the risk of T2D. So far, published cohort studies and meta-analyses have reported inconsistent findings.

To address this uncertainty, researchers conducted a cohort study and a dose-response meta-analysis to better define the relationship between tea consumption and future T2DM risk.

First, they studied 5,199 adults (2583 men, 2616 women) with no history of T2D (average age 42) from the China Health and Nutrition Survey (CHNS), who were recruited in 1997 and followed until 2009. The CHNS is a multicentre prospective study looking at the economics, sociological issues and health of residents from nine provinces.

At the outset, participants filled in a food and drink frequency questionnaire and provided information on lifestyle factors such as regular exercise, smoking and alcohol consumption. Overall, 2,379 (46%) participants reported drinking tea, and by the end of the study, 522 (10%) participants had developed T2D.

After adjusting for factors that are known to be linked with increased risk of T2D, like age, sex, and physical inactivity, researchers found that tea drinkers had a similar risk of developing T2D compared to non-drinkers. And the results did not change significantly when analysed by age and sex, or when participants who developed diabetes during the first 3 years of follow-up were excluded.

In the next step of the study, the researchers did a systematic review of all cohort studies investigating tea drinking and the risk of T2D in adults (aged 18 or older) up to September 2021. Overall, 19 cohort studies involving 1,076,311 participants from eight countries [1] were included in the dose-response meta-analysis.

They explored the potential impact of different types of tea (green tea, oolong tea, and black tea), frequency of tea drinking (less than 1 cup/day, 1-3 cups/day, and 4 or more cups/day), sex (male and female), and the location of the study (Europe and America, or Asia), on the risk of T2D.

Overall, the meta-analysis found a linear association between tea drinking and T2D risk, with each cup of tea consumed per day reducing the risk of developing T2D by around 1%.

When compared with adults who didn’t drink tea, those who drank 1-3 cups daily lowered their risk of T2D by 4%, while those who consumed at least 4 cups every day reduced their risk by 17%.

The associations were observed regardless of the type of tea participants drank, whether they were male or female, or where they lived, suggesting that it may be the amount of tea consumed, rather than any other factor, that plays a major role.

“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)”, says Li.

She adds, “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. 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.”

Oolong tea is a traditional Chinese tea that’s made from the same plant used to make green and black teas. The difference is how the tea is processed—green tea is not allowed to oxidise much, black tea is allowed to oxidise until it turns black, and oolong tea is partially oxidised.

Despite the important findings, the authors note that the study is observational and cannot prove that drinking tea reduced the risk of T2D, but suggests that it is likely to contribute.

And the researchers point to several caveats, including that they relied on subjective assessments of the quantities of tea consumed and they cannot rule out the possibility that residual confounding by other lifestyle and physiological factors may have affected the results.

No paper yet published!

sciencesources.eurekalert.o...

36 Replies
greygoose profile image
greygoose

Also, how big is the cup?

Lulu2607 profile image
Lulu2607

hi Helvella. Is this yet another correlational study being presented as fact? The word 'linked' gives it away. As you suggest from your comments about extraneous factors ( size of cup, any additions to the tea etc) and poor control, this is sloppy science. And subjective assessments are definitely weak science. I could go on with the criticisms but will resist, but so called scientific reports should not get past peer review stage. Causation cannot be proved by a correlation, but the media print such nonsense frequently. Thanks for passing on the info. however.

helvella profile image
helvellaAdministrator in reply to Lulu2607

I feel it better to have a discussion here and now than to see it come round in the many forms that such "studies" are cycled and recycled!

Sparklingsunshine profile image
Sparklingsunshine in reply to helvella

Hi

Over the years I've seen tea, green or black linked with everything from cancer prevention, reduced dementia and weight loss. But most studies caveat and say may help with,rather than actually do.

Like most people I drink tea because I like it. I drink tea with milk and green and oolong tea without. If it has health benefits then geat but I drink them for enjoyment purposes primarily.

humanbean profile image
humanbean

In what I have been able to read, the effect of sugar (and other sweeteners) appears to be ignored. Doesn't that even suggest itself as a factor in the context of diabetes?

Not relevant to anyone but me but... I am sooooo glad I was sensible enough to give up sugar in tea and coffee when I was 13!

Sparklingsunshine profile image
Sparklingsunshine in reply to humanbean

Hi

I gave up sugar about 6 years ago. I never used sweetners because they really suck, I did used to like 1 sugar in a cup of tea or coffee though. When I gave up sugar I also gave up drinking any soft drinks as well.

The first week or two without sugar was tough and weird but now I can't imagine drinking sweet tea or coffee. Still dont drink soft drinks and I never developed a fizzy drink habit thankfully.

TSH110 profile image
TSH110 in reply to Sparklingsunshine

never been keen on fizzy or soft drinks but I used to lob a lot ofsugar in my tea. I couldn’t drink it sugared now - it’s so sickly tasting

nellie237 profile image
nellie237 in reply to humanbean

I gave up sugar in hot drinks in my teens too. I didn't find it difficult to do, but I expect it becomes more difficult the older you get. Giving up cigarettes......that was hard.

humanbean profile image
humanbean in reply to nellie237

I was a heavy smoker, and I smoked for a very long time, but I gave up about 13 years ago. And yes, giving up was extremely difficult.

If I wanted to guess what I'm most likely to die of I know what I would put top of the list.

Sparklingsunshine profile image
Sparklingsunshine in reply to nellie237

Hi

I used to smoke when i was younger, never a heavy smoker but enough, getting a nasty dose of the flu followed by pleurisy was enough to persuade me to quit. I found it easy which then made me wish I'd done it sooner. Newrly 30 years since I last had a puff.

TSH110 profile image
TSH110 in reply to nellie237

Best think I ever did, knocked a 60 a day habit on the head. I used Alan Carr’s the easy way to stop smoking book, it really helped as the physical addiction passes after two weeks (it was the hardest part) after that it’s all psychological addiction. Knowing that really helped me. For years after I’d dream I was pontificating about having stopped smoking then I’d sneak off somewhere like a cellar and have a crafty fag! I still have dreams that I am a smoker and my stopping is nothing more than a charade. I haven’t smoked for 33 years! And I never touched one ever again except in my dreams. Perhaps it’s a subconscious warning? But. I’ve never wanted to start again.

Zephyrbear profile image
Zephyrbear in reply to TSH110

I did exactly the same as you! I was a 20-a-day for 35 years and not even watching my dad die of lung cancer could help me to stop. Then my daughter gave me this book and I read it in one day! (loved the chapter on the benefits of smoking) As instructed by the book, I carried on smoking while I was reading it and on finishing it, I collected up all my ashtrays, washed them up and put them away. I gave the remaining two packs of cigarettes to my brother and I haven’t had a single cigarette since! That was 18 years ago and after the first day I didn’t have any problems with cravings at all! I always recommend that book to anyone who asks.

TSH110 profile image
TSH110 in reply to Zephyrbear

I still have the packet of golden Virginia rolling tabaco I kept because I thought if I could and didn’t I had truly stopped. It’s a bit darn crispy to the touch! The packet of rízla papers that were with it have vanished tho.

helvella profile image
helvellaAdministrator in reply to TSH110

I have a couple of packs of fag papers!

TSH110 profile image
TSH110 in reply to helvella

that explains it 🤣🤣🤣

Zephyrbear profile image
Zephyrbear in reply to TSH110

Hahaha! That’ll be like smoking the Dead Sea Scrolls by now then! I remember having some of that baccy after it had gone a bit dry… the trick was not to let it fall out before you’d lit it! 😂🤣😂

TSH110 profile image
TSH110 in reply to Zephyrbear

🤣🤣🤣

helvella profile image
helvellaAdministrator in reply to humanbean

Choice of the actual tea or coffee seems more important when not using any form of sweetener (neither any form of sugar nor non-sugar sweeteners).

Relentlesssearch profile image
Relentlesssearch

helvella are you a researcher?

helvella profile image
helvellaAdministrator in reply to Relentlesssearch

Just a patient. :-)

Relentlesssearch profile image
Relentlesssearch in reply to helvella

I want to get better at research but have never been very good at it 🤔 you seem to be able to do it very well! Have you got on top of your conditions?

helvella profile image
helvellaAdministrator in reply to Relentlesssearch

I'm not doing too badly, thank you!

My Vade Mecum document has an Appendix full of what I consider some of the best online resources. In fact, pretty much the whole document is a series of pointers to help anyone find out more.

Maybe you'd get some ideas from having a look? :-)

helvella - Vade Mecum for Thyroid

The term vade mecum means:

1. A referential book such as a handbook or manual.

2. A useful object, constantly carried on one’s person.

Please don't get put off by the number of pages!

Nor by the fact it is targeted at people interested in thyroid issues. Much of its contents could be of use to many involved in health issues. Things like abbreviations, lists, general reference information, an Appendix of links to many useful websites.

And do keep up to date. I edit it frequently- sometimes trivially, sometimes extensively. If your copy is more than a few weeks old, please download it again.

In particular, it is not intended that you sit and read the document. Just that you download it and know you can look things up.

If there is anything you'd like me to add, let me know.

From Dropbox:

dropbox.com/s/vp5ct1cwc03bl...

From Google Drive:

drive.google.com/file/d/1P9...

Relentlesssearch profile image
Relentlesssearch in reply to helvella

you’re so very kind (and clever!) to have made this for us all. I feel so lucky! I will enjoy delving into this very much. Thank you for all the effort and time spent on this, I think I’ll find it invaluable

Relentlesssearch profile image
Relentlesssearch in reply to helvella

I have read through the document very quickly, thank you so much I think it will help so much in my studies. Do you think you’ll add anything about cortisol and/or how to get optimal on thyroid hormone/obstacles that make us come unstuck/unable to take medications?

helvella profile image
helvellaAdministrator in reply to Relentlesssearch

Anyone who compiles a big document ends up with the same issues. Where to stop being a big one.

Yes, I know there are strong connections between adrenals, cortisol and thyroid, but I don't feel confident including much about them. I'll give it some thought but will probably not add much.

However I'll definitely consider adding more in the areas of optimisation and problems. Don't hold your breath! I tend to do nothing for ages - just mull it over. Then have a burst of activity.

Please do make as many suggestions as you come up with. And remind me if I haven't done anything I said I would. :-)

Relentlesssearch profile image
Relentlesssearch in reply to helvella

I’m in the process of collating some bits and pieces re. Optimisation as I try to work on my own situation - I would be very willing to share anything I come across with you 😊 I am also training to become a naturopath at the moment, so I may be able to help you develop things re. Lifestyle & dietary factors that influence thyroid optimisation as well vits, mins and meds x

TSH110 profile image
TSH110

it’s also thought to have been key in Britain’s lead in the industrial revolution:

amp.theguardian.com/comment...

helvella profile image
helvellaAdministrator in reply to TSH110

And a major issue in World War II:

Strange But True: During WWII the British Government Bought all of The World’s Tea

warhistoryonline.com/instan...

(I have not done any fact checking on this!)

TSH110 profile image
TSH110 in reply to helvella

A very good read!

I agree with Orwell on how best to make it:

orwellfoundation.com/the-or...

helvella profile image
helvellaAdministrator in reply to TSH110

No need for any milk!

TSH110 profile image
TSH110 in reply to helvella

I might disagree on that point - missed it!

TSH110 profile image
TSH110

looks like it’s choc full of “stuff” that could well be beneficial:

ncbi.nlm.nih.gov/pmc/articl...

Mary Cassat Painting : The Cup of Tea
Doris11 profile image
Doris11

yay 🥰🥰🥰

Danielj1 profile image
Danielj1

they say the same at times about coffee - and for a while I absolutely followed this approach.

but tea and coffee seem to shred magnesium levels which are a real issue for hypo folks anyway so you need to really up the magnesium dosage to compensate

After a long while, I just don’t think the pros and cons stack up and you can get better results with other means - recent blood tests over glucose tolerance have absolutely validated this in my specific case

Margareta3 profile image
Margareta3

But it may highly increase the risk of developing thyroid problems because of substantial levels of fluoride in tea. Every stick has got two ends.....

helvella profile image
helvellaAdministrator in reply to Margareta3

Maybe. But I think that if you observe a group of people and see that some drink tea, while others don't, and see an association as described, the fluoride consumption of the tea-drinkers will be factored in.

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