A more manageable three to four cups a day was associated with a 13 percent reduction in diabetes risk, which consuming between eight and 11 cups was associated with a 22 percent risk reduction, according to findings of a study in a population with a high incidence and prevalence of diabetes.
“The potential effects of high level of coffee consumption on risk of type 2 diabetes may be important but should be considered in light of putative health effects of coffee, such as potential detrimental effects on blood pressure and sleep quality,” cautioned researchers from the University of Oklahoma and the National Heart, Lung and Blood Institute.
Writing in the Nutrition, Metabolism and Cardiovascular Diseases, they added that further studies are required to establish if the association found in this study is causal or not.
The results are consistent with a growing body of research, much of which was pulled together in a meta-analysis in the Archives of Internal Medicine (Dec 2009, Vol. 169, pp. 2053-2063) by scientists from the University of Sydney, Australia. Data from over 500,000 individuals with over 21,000 cases of type-2 diabetes from prospective studies showed that drinking three to four coffee and tea may reduce the risk of developing diabetes by 25 per cent.
Benefits of the bean
Coffee, one of the world's largest traded commodities produced in more than 60 countries and generating more than $70bn in retail sales a year, continues to spawn research and interest with data linking it to improved liver health, in addition to the potential anti-diabetes benefits.
Diabetes affects an estimated 24 million Americans, equal to 8 percent of the population. The total costs are thought to be as much as $174 billion, with $116 billion being direct costs from medication, according to 2005-2007 American Diabetes Association figures.
Data on coffee consumption from 1,141 Native Americans men and women aged between 45 and 74. The prevalence of diabetes in this population is established to be betwene 40 and 70 percent, said the researchers. All of the participants were deemed to have normal glucose tolerance, and free of diabetes at the start of the study.
After 7.6 years of follow-up the researchers calculated that people with the highest coffee intake of 12 or more cups a day, which was consumed by 8 percent of the participants, had an associated 67 percent lower risk of developing diabetes, compared to non-drinkers.
Bioactives in the bean
Commenting on the potential mechanism, the researchers noted that the potential benefits may be related to the antioxidant content of the beverage may counter the oxidative stress which may cause dysfunction of beta cells and endothelium and boost insulin resistance.
Another potential mechanism involves the chlorogenic acid content of coffee and the compounds it forms on degradation, with previous studies linking these degradation products to reduced glucose absorption in the intestine.
The magnesium content of coffee may also play a role in the potential reduction in the risk of type 2 diabetes, said the researchers.
“Further studies on the biological mechanisms relating consumption are needed,” they added.
Source: Nutrition, Metabolism and Cardiovascular Diseases
Published online ahead of print, doi: 10.1016/j.numecd.2009.10.020
"Coffee consumption and the incidence of type 2 diabetes in men and women with normal glucose tolerance: The Strong Heart Study"
Authors: Y. Zhang, E.T. Lee, L.D. Cowan, R.R. Fabsitz, B.V. Howard