Five cups of coffee per day for two months were associated with significant metabolic benefits and live function, according to findings of a study published in the Nutrition Journal.
The study adds to an ever growing body of science supporting the potential health benefits of the beverage, and its constituent ingredients.
Coffee, one of the world's largest traded commodities and generating more than $70bn in retail sales a year, has come under increasing study with research linking it to reduced risk of diabetes, and improved liver health.
The new study – led by Nicole Wedick, ScD., from the Harvard School of Public Health – also found that the metabolic benefits were more pronounced in caffeinated coffee, a result that supports the hypothesis that caffeine is responsible for some of the apparent benefits.
Coffee is also a rich source of polyphenols: A recent report by Mario Ferruzzi from Purdue University in Physiology & Behavior (doi: 10.1016/j.physbeh.2010.01.035) stated that one cup of the stuff could provide 350 milligrams of phenolics.
Of these, the most abundant compounds in coffee are chlorogenic acids, making up to 12 per cent of the green coffee bean. The most abundant of these compounds is caffeic acid.
Dr Wedick and her colleagues recruited 45 healthy, overweight coffee drinking 40 year olds to participate in their randomized trial. The volunteers were asked to drink five cups of coffee per day of instant caffeinated coffee, decaffeinated coffee, or water for eight weeks.
Results of the study showed that caffeinated coffee consumption was associated with a 60% reduction in blood levels of a compound called interleukin-6, which can promote inflammation, compared with the water group.
In addition, levels of adiponectin – a hormone released from fat cells that plays an important role in the regulation of insulin sensitivity and energy – also decreased in the caffeinated, but not decaffeinated group.
On the other hand, coffee consumption didn’t seem to influence blood sugar or insulin levels during the eight weeks of study.
“Our findings suggest that improvements in adipocyte and liver function […] may contribute to beneficial metabolic effects of long-term coffee consumption,” wrote the Boston-based scientists.
“Given the popularity and widespread consumption of coffee, the effects of coffee and coffee components on metabolic risk factors warrant further investigation.”
A meta-analysis published in the Archives of Internal Medicine in 2009 concluded that consumption of three to four coffee may reduce the risk of developing diabetes by 25 per cent. The potential bioactive compounds in the beverage responsible for the reported benefits may include magnesium, antioxidant lignans or chlorogenic acids.
According to the World Health Organisation (WHO), diabetes affects over 220 million people globally and the consequences of high blood sugar kill 3.4 million every year. The WHO is predicting deaths to double between 2005 and 2030.
The total costs associated with the condition in the US alone 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.
Source: Nutrition Journal
2011, 10:93 doi:10.1186/1475-2891-10-93
“Effects of caffeinated and decaffeinated coffee on biological risk factors for type 2 diabetes: A randomized controlled trial”
Authors: N.M. Wedick, A.M. Brennan, Q. Sun, F.B. Hu, C.S. Mantzoros, R.M. vanDam