The study – published in BMJ Open –assessed the black tea consumption rates of 42 different countries and analysed them against each country’s rates of respiratory, infectious and cardiovascular disease, as well as cancer and diabetes.
Led by researchers at Swiss research agency Data Mining International, in partnership with Unilever, the team report a linear correlation between the quantity of black tea consumed and the incidence of diabetes across the 42 nations – with the research revealing that on average, a population that consumes double the amount of black tea to another has about one quarter less cases of diabetes.
“This is the first time that a robust statistical relationship has been established between black tea consumption and diabetes prevalence in the world,” said Dr Ariel Beresniak, chief executive officer of Data Mining International.
Professor Genevieve Berger, chief research & development officer at Unilever – and co-author of the study – said the research adds to “a growing body of evidence which points to black tea’s health-giving properties.”
“Further investigation is required to understand if there is a causal relationship between the two, but the fact that populations which drink lots of black tea suffer less cases of diabetes is an interesting finding, and one which gives us good cause to carry out more research to further understand the driving factors behind this exciting research.”
The global prevalence of type 2 diabetes has increased six-fold over the past few decades. The International Diabetes Federation calculates that the number of those with the disease will soar from 285 million in 2010 to 438 million in 2030.
“While we cannot confirm a cause-effect relationship between tea drinking and diabetes, our findings are consistent with a number of biological, physiological, epidemiological and clinical studies suggesting that black tea components have a positive effect on glucose metabolism,” added Beresniak.
Berger and her colleagues systematically mined information on black (fermented) tea consumption in 50 countries across every continent, based on 2009 sales data collected by Euromonitor (World Tea Consumption Survey).
In this data, Ireland topped the league table for black tea drinkers, at more than 2 kilograms per year per person. This was closely followed by the UK and Turkey. At the bottom of the table were South Korea, Brazil, China, Morocco and Mexico, with very low consumption.
Using data from the World Health Survey, conducted by the World Health Organization, the team then assessed tea consumption against rates of cancer, diabetes, and respiratory, infectious and cardiovascular disease.
The only correlation found was between population black tea consumption and diabetes prevalence, they said. This link was then confirmed with further statistical analysis, which pointed to a strong linear association between low rates of diabetes in countries where consumption of black tea is high.
Source: BMJ Open
Published online, Open Access, doi: 10.1136/bmjopen-2011-000648
“Relationships between black tea consumption and key health indicators in the world: an ecological study”
Authors: Ariel Beresniak, Gerard Duru, Genevieve Berger, Dominique Bremond-Gignac