Düsseldorf, Germany - A small study published this week points again to the beneficial effects of coffee consumption. Researchers showed that drinking coffee led to improved markers of subclinical inflammation and oxidative stress, as well as increases in HDL-cholesterol levels [1].

"We found some evidence of beneficial effects on the lipid profile, but no effects on glucose metabolism," report lead investigator Dr Kerstin Kempf (University Düsseldorf, Germany) and colleagues. "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."

Writing in the April 2010 issue of the American Journal of Clinical Nutrition, the researchers add that previous studies have shown that drinking coffee protects against developing type 2 diabetes mellitus, possibly through reductions in inflammation, oxidative stress, and favorable changes in the lipid profile.

In this study of 47 habitual coffee drinkers, the individuals stopped drinking coffee for one month. In the next month, they drank four cups of coffee per day, followed by eight cups of coffee daily in the second month. Subjects were relatively healthy, younger than 65 years of age, but with an increased risk of diabetes based on a diabetes risk score.

After the two months of subjects drinking coffee, the researchers observed significant decreases in markers of subclinical inflammation, including interleukin-18 (IL-18) and adiponectin, but no increases in levels of C-reactive protein (CRP). Markers of oxidative stress, on the other hand, were significantly reduced.

"There was a significant decrease in circulating IL-18 concentrations, but no changes in systemic CRP or IL-6 concentrations," write Kempf and colleagues. "We previously identified higher concentrations of IL-18 as a risk factor for type 2 diabetes."

Regarding the lipid parameters, the researchers report that total-cholesterol levels were significantly increased, by 12%, after the second month of drinking coffee. In addition, apolipoprotein A1 levels were also significantly increased. HDL-cholesterol levels were up 7%, from 48 mg/dL to 51 mg/dL, by the end of the second month.

There were no changes in any markers of glucose metabolism. According to the researchers, this "noteworthy" finding might be explained by the short duration of the trial compared with coffee consumption over years in prospective studies. They say the favorable effects on HDL cholesterol should be investigated further.