Incidents of type 2 diabetes appear lower in countries where consumption of black tea is high, according to a mathematical analysis of health research in 50 countries.
The analysis, published in the , suggests residents of countries such as Ireland, UK, and Turkey derive some protection from drinking black tea.
Data included sales figures collected by a market research firm and medical statistics reported by World Health Organization on the prevalence of respiratory, infectious, and cardiovascular diseases including cancer and diabetes.
Further analysis confirmed a strong linear association between low rates of diabetes in countries and high black tea consumption. The global prevalence of type 2 diabetes has increased six fold over the past few decades, and 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.
Among the countries studied, Ireland had the highest rate of black tea consumption at more than 2 kg a year per person, followed by the UK, and Turkey.
South Korea, Brazil, China, Morocco, and Mexico recorded very low consumption.
Researchers speculate that the process that turns green tea black creates a range of complex flavonoids, including theaflavins and thearubigins, to which several potential health benefits have been attributed.
In a 2009 study published in the Journal of Food Science, for example, researchers found that polysaccharides, a type of carbohydrate that helps delay the absorption of glucose, was the most effective in black tea.
“These original study results are consistent with previous biological, physiological, and ecological studies conducted on the potential of [black tea] on diabetes and obesity, and they provide valuable additional scientific information at the global level,” according to the report.