Scientists from Germany, Finland and Denmark report that daily coffee consumption was associated with improved cholesterol levels and blood levels of inflammatory compounds such as interleukin-18.

“Our study represents the first intervention trial to investigate the anti-inflammatory effect of coffee and to develop and test coffee-derived compounds in plasma as biomarkers of coffee intake during long-term coffee consumption,” stated the researchers, led by Christian Herder from Heinrich Heine University Dusseldorf.

Writing in the American Journal of Clinical Nutrition, the European scientists also note: “Coffee consumption appears to have favourable effects on some markers of subclinical inflammation and oxidative stress and to increase plasma concentrations of potential biomarkers of coffee intake.

“Because subclinical inflammation is a risk factor for type 2 diabetes, our results suggest one mechanism that could mediate the reduced risk of type 2 diabetes among individuals who habitually consume coffee for years.”

Coffee and its extracts

The beverage, and its constituent ingredients, has come under increasing study with research linking it to reduced risk of diabetes, and improved liver health.

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.

Indeed, a recent report by Mario Ferruzzi from Purdue University in Physiology & Behavior (doi: 10.1016/j.physbeh.2010.01.035) stated that coffee is one of the richest sources of polyphenols in the Western diet, with one cup of the stuff providing 350 milligrams of phenolics. Of these, the most abundant compounds coffee are chlorogenic acids, making up to 12 per cent of the green coffee bean. The most abundant of these compounds is caffeic acid.

New data

The new study, supported financially by the Institute of Scientific Information on Coffee, which is a consortium of major European coffee companies, involved 47 regular coffee drinkers. The participants stopped drinking the beverage for one month, then llimited themselvs to four cups a day for another month, and then drank eight cups per day for a third month.

Results showed that blood levels of caffeine, chlorogenic acid, and caffeic acid metabolites increased following coffee consumption. Furthermore, levels of the pro-inflammatory interleukin-18 and 8-isoprostane (a marker of oxidative stress) decreased by 8 and 16 per cent, respectively.

Furthermore, adiponectin levels increased by 6 per cennt. Adiponectin is a protein hormone linked to various metabolic processes, and levels are inversely related to body fat levels.

Improvements in cholesterol levels were also detected following the third month, with total cholesterol and HDL cholesterol increased by 12, 7, and 4, respectively. On the other hand, the ratios of LDL to HDL cholesterol decreased by 8 per cent, they added. Glucose metabolism was unaffected by coffee consumption.

“It is noteworthy that our study showed no effects of coffee on fasting and oral-glucose-tolerance-test– derived markers of glucose metabolism,” wrote Herder and his co-workers. “We cannot exclude that the short duration of the present trial compared with coffee consumption over years in prospective studies could have contributed to this null result.

“Although we report herein favorable effects of coffee on IL-18 and adiponectin, which have been implicated in the risk of type 2 diabetes, the changes observed we observed were smaller than the differences between baseline concentrations of these markers in low- and high-risk individuals,” they added.

Despite the null result regarding glucose metabolism, the researchers concluded that the impact of inflammation on the progression of diabetes may support an anti-diabetic role for the beverage.

Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: doi:10.3945/ajcn.2009.28548
"Effects of coffee consumption on subclinical inflammation and other risk factors for type 2 diabetes: a clinical trial"
Authors: K. Kempf, C. Herder, I. Erlund, H. Kolb, et al.

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