Feb. 1, 2000 (Atlanta) -- Volunteers drinking daily doses of thick, French-press coffee -- a full liter of unfiltered brew -- have helped move scientific research closer to establishing a true link with coffee and heart disease risk, according to a study from the February issue of the American Journal of Clinical Nutrition.
Previous studies have pointed to a link between coffee drinking and increased levels of homocysteine, a blood component that has been associated with heart disease risk, but the study results have not been consistent. In the first controlled study testing this link, however, Dutch researchers showed that it exists -- at least when six cups of unfiltered coffee are consumed daily.
Lead author Marina J. Grubben, MD, of the University Hospital Nijmegen's department of gastroenterology and hepatology, says, "It is unclear whether the effect is caused by the cholesterol-raising diterpenes present exclusively in unfiltered coffee or by factors that are also present in filtered coffee." Diterpenes are naturally present in coffee, but are removed by filtering. Most Americans drink filtered coffee.
The study involved 64 volunteers, men and women ranging from 24 to 70 years old, all of whom had normal homocysteine levels. Half consumed one liter of unfiltered French-press coffee -- coarse-ground coffee consisting of an arabica/robusta bean blend, a favorite in the Netherlands.
Coffee was prepared for the volunteers every day in the traditional manner, using a plunger. The control group consumed no coffee, but instead drank water, milk, chocolate drinks, tea, or broth.
During the eight-week study period, volunteers drank their assigned beverages in two-week shifts. Fasting blood samples were taken on day 15 of each shift, and then volunteers took one week off. During the second and third shifts, the groups switched their assigned drinks, so that everyone drank coffee at some point. Volunteers were instructed to drink the entire liter, or about six cups, each day.
The researchers found that fasting plasma homocysteine concentrations increased by 10% -- which could increase the risk of heart disease by 10%, Grubben says.
Thinking that other dietary components might cause the increased levels, researchers also assessed each volunteer's diet during the study period. They found no link between diets and homocysteine elevations.
"It is still unknown whether a reduction in moderately elevated homocysteine concentrations will also reduce the risk of cardiovascular disease. [Studies] are underway that may answer this question," says Grubben. "Our results only apply to heavy coffee drinkers."
In an accompanying editorial, Stein Emil Vollset and colleagues write, "Until now, no [controlled] studies have addressed the issue. Therefore, the study by Grubben et al., is most welcome. ? However, on the basis of current knowledge, these results should not cause additional concern for the general public, who still may enjoy drinking coffee."
When asked for objective commentary, Dean Jones, PhD, director of Emory University's nutrition program, tells WebMD, "I thought it was a very well-designed study ? probably the best study of its type on [homocysteine and coffee]."
Jones adds, "The problem is ? how much can you generalize from it? Six cups of coffee, that's pushing it. It really doesn't tell us anything about what lower coffee consumption would be. Also, with the issue of unfiltered coffee, they obviously wanted to maximize their chances of seeing something. The reality is, that's not the common type of coffee. It's a good study, but it's just impossible to extrapolate to our common use. It tells us that coffee is a risk, but we just don't know for more moderate consumption what that problem would be."