Black Tea Protects Against Diabetes

black tea and diabetes

If you drink tea regularly, your favourite cuppa is helping to protect you from type 2 diabetes – as long as it is unsweetened. A large analysis which looked at data from over 545,500 people, found a clear relationship between the number of cups of tea drunk per day, and the risk of developing type 2 diabetes.

Compared with those who drank no tea, the relative risk of developing type 2 diabetes was:

  • 3% lower for those drinking one cup of tea per day
  • 5% lower for those drinking two cups of tea per day
  • 7% lower for those drinking three cups of tea per day
  • 10% lower for those drinking four cups of tea per day
  • 12% lower for those drinking five cups of tea per day
  • and 15% lower for those drinking six cups of tea per day.

Despite scouring the paper, I could not find their working definition for ‘one cup of tea’ so have to assume it was a standard U.S. 250ml cup of medium-strength tea, with or without milk, rather than a huge builder’s mug of ultra-strong brew.

How tea protects against diabetes

It’s always exciting when a study finds a clear dose-response, as this immediately suggests the present of active ingredients having a real biological effect. Two new studies now appear to confirm the mechanism behind tea’s significant anti-diabetes action.

Black tea, green and oolong tea leaves contain high levels of antioxidant polyphenols which block a key group of digestive enzymes – pancreatic alpha-amylase and intestinal alpha glucosidases. These enzymes break down starchy carbohydrates to release glucose, and by blocking them, tea damps down the rise in blood glucose levels that normally occurs after eating.

This action is identical to that of the diabetic drug, acarbose, which is classed as an alpha-glucosidase inhibitor. In fact, the effects of drinking black tea appear to be synergistic with those of acarbose. This suggests that drinking black (or green) tea with, or just after a meal, could act as a true nutritional medicine to prevent the onset of type 2 diabetes – or to postpone the need for drug medication in those at risk.

My favourite tea is Birchall’s Great Rift which has an amazing fresh, aromatic taste. For a more intense flavour, brimming with polyphenols, then Yorkshire Tea from Taylors of Harrogate is difficult to beat.

If you are on medication to lower your blood glucose levels, it’s possible that dramatically changing the amount of tea you drink could affect your glucose control. If you want to drink more (or less) tea, check your blood glucose levels regularly and ensure you know how to adjust your medication accordingly.

If in doubt, talk to your doctor.

Red wine provides similar benefits

There’s good news for those who love an occasional glass of red wine, too. Red wine contains similar polyphenols to those in black tea leaves – and yes, red wine can also inhibit alpha-glucosidase enzymes. White wine also has an effect, though this is 80% less impressive than with red wine.

I hesitate to recommend drinking red wine to protect against diabetes – I would probably get struck off the medical register – but at least you don’t need to feel guilty about enjoying the odd glass of fermented red grape juice every now and then.

Image credit: Tea Advisory Panel

About Dr Sarah Brewer

QUORA EXPERT - TOP WRITER 2018 Dr Sarah Brewer MSc (Nutr Med), MA (Cantab), MB, BChir, RNutr, MBANT, CNHC Cert IoD qualified from Cambridge University with degrees in Natural Sciences, Medicine and Surgery. After working in general practice, she gained a master's degree in nutritional medicine from the University of Surrey. Sarah is a registered Medical Doctor, a registered Nutritionist and a registered Nutritional Therapist. She is an award winning author of over 70 popular self-help books and a columnist for Prima magazine.

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