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Black Tea Linked to Lower Diabetes Risk

By Salynn Boyles
WebMD Health News

Reviewed by Louise Chang, MD

Nov. 7, 2012 -- Drinking black tea may help protect against type 2 diabetes, but more study is needed to confirm an association.

When researchers analyzed data from 50 countries, they found that the rate of diabetes was lowest in countries where people drank the most black tea.

Type 2 diabetes rates have skyrocketed worldwide in recent decades. It's projected that by 2030 there will be over 900 million people across the globe with diabetes or with a high risk for developing it.

When researchers used a mathematical model to estimate the impact of drinking black tea on a number of health conditions, they found a link to just one -- diabetes.

Of the countries included in the analysis, black tea drinking was highest in Ireland, the U.K., and Turkey. It was lowest in South Korea, Brazil, and China.

Researcher Ariel Beresniak, MD, PhD, of the mathematical research group Data Mining International in Geneva, Switzerland, says the study shows a consistent relationship between black tea drinking and type 2 diabetes risk. But this study does not prove a cause and effect relationship.

Black tea may protect against diabetes, Beresniak says, but more research is needed to prove this.

"You certainly can't say that on the basis of this study alone, but the findings are consistent with previous studies that have also suggested a link," he says.

The new study was published today in the journal BMJ Open.

Role of Green Tea and White Tea

Studies have also linked green tea and white tea to a lower risk of diabetes, but Beresniak and colleagues were not able to examine this association.

Black tea is more highly fermented and, as the name suggests, darker, than green or white tea.

The fermentation process turns simple flavonoid compounds called catechins in green tea into complex compounds called theaflavins and thearubigins.

Beresniak says if black tea is shown in future research to actually lower diabetes risk, the fermentation process may explain why.

Diabetes specialist Spyros Mezitis, MD, of Lenox Hill Hospital in New York City, says while there is probably no harm in drinking tea, there is as yet no compelling reason to recommend that patients with diabetes or those at risk for the disease drink tea.

"I am not convinced on the basis of this study that drinking black tea lowers diabetes risk," he says.

He adds that dietary and other lifestyle choices known to lower diabetes risk include:

  • Limiting foods that contain refined sugar and highly refined white flour.
  • Adding fruits, vegetables, whole grains, and low-fat dairy to your diet.
  • Getting at least 30 minutes of aerobic exercise, at least three times a week.

"These are things that we know will make a difference," he says.

SOURCES: Beresniak, A. BMJ Open, Nov. 7, 2012. Ariel Beresniak, MD, PhD, department of research, Data Mining International, Geneva, Switzerland. Spyros Mezitis, MD, endocrinologist, Lenox Hill Hospital, New York City. News release, BMJ Group.

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