WASHINGTON — Decaffeinated — not caffeinated — coffee may cause an increase in harmful L.D.L. cholesterol by increasing a specific type of blood fat linked to the metabolic syndrome, according to a new study presented at the American Heart Association’s Scientific Sessions 2005.
The Coffee and Lipoprotein Metabolism (CALM) study included 187 people, randomized to three groups: one that drank three to six cups of caffeinated coffee a day; another that drank three to six cups of decaffeinated coffee a day; and a third, the control group, that drank no coffee.
Some studies have linked coffee drinking to heart disease, but others have suggested that it is not harmful.
"The problem with the results from these previous studies is that many of them were association studies, which looked broadly at free-living populations and drew associations between lifestyle factors, volitional coffee consumption, and disease risk," said H. Robert Superko, M.D., lead author of the study and chairman of molecular, genetic and preventive cardiology at the Fuqua Heart Center and the Piedmont-Mercer Center for Health and Learning in Atlanta. "Our study randomized subjects to a specific type and amount of coffee consumption, brewed in a standardized manner, just like a drug study."
As part of the study, researchers gave participants a nationally popular home-brewed caffeinated coffee and decaffeinated coffee brand, and coffee makers. Researchers then instructed participants on how to prepare the coffee in a standardized manner and asked them to drink only this coffee. All participants drank only black coffee.
"Whether coffee has caffeine is not the only thing that differentiates caffeinated from decaffeinated types," Mr. Superko said. "Caffeinated and decaffeinated coffees are often made from different species of beans. Caffeinated coffee, by and large, comes from a bean species called coffee Arabica, while many decaffeinated coffees are made from coffee Robusta. The decaffeination process can extract flavonoids and ingredients that give coffee flavor. So decaffeinated brands usually use a bean that has a more robust flavor."
Researchers measured the level of caffeine in the blood of the participants, as well as levels of the key heart-health indicators before and after the three-month study.
They sought to clearly demonstrate the effects of caffeinated and decaffeinated coffee consumption on key indicators of the metabolic syndrome, which is the umbrella term for a cluster of several harmful heart disease risk factors. Researchers looked at blood pressure, heart rate, body mass index, total cholesterol, triglycerides, H.D.L. (good cholesterol) levels of insulin, glucose, non-esterified fatty acids (NEFA — fat in the blood), apolipoprotein B (ApoB — a protein associated with L.D.L. or "bad" cholesterol) and high-density lipoprotein 2 (H.D.L.2 — a type of "really good" cholesterol).
Researchers found no significant changes among the three groups’ levels of blood insulin and glucose, or other major risk factors.
But they reported for the first time that, after three months of coffee drinking, the decaffeinated group experienced a rise in fatty acids, which is the fuel in the blood that may drive the production of low-density lipoprotein L.D.L.
ApoB rose 8% in the decaffeinated group but did not significantly change in the other two groups. ApoB is the only protein attached to L.D.L., and studies show that ApoB might be a better predictor of cardiovascular disease risk than one’s L.D.L. level.
NEFA rose an average 18% in the decaffeinated group, while it did not change in the other two groups.
"NEFA is the fuel that can drive the increase in ApoB and L.D.L.," Mr. Superko said. "These results are very surprising and have never been reported before for coffee consumption. This is the first non-industry-sponsored study of its kind. Until now, researchers had not reported on a randomized prospective study looking at the mechanism of how a particular kind of coffee consumption increases ApoB and L.D.L.-cholesterol.
"There is a real difference between caffeinated and decaffeinated coffee and, contrary to what people have thought for many years, I believe it’s not caffeinated but decaffeinated coffee that might promote heart disease risk factors that are associated with the metabolic syndrome, an expanding heart-health hazard in the United States."
In measuring H.D.L. cholesterol, researchers looked specifically at H.D.L.2, a type of H.D.L. in which high levels are particularly associated with lower risk of heart disease. They found that H.D.L.2 didn’t change significantly overall among the three groups in the study. But in the decaffeinated group, it changed significantly according to participants’ body fat.
For those who had body mass indexes (B.M.I.s) of more than 25 (considered overweight), drinking decaffeinated coffee increased H.D.L.2 by about 50%. But those in the decaffeinated group, who were not considered overweight according to B.M.I., saw their H.D.L.2 drop by about 30%.
"This illustrates to the public that this is not a simple story of one coffee is good, one coffee is bad," he added. "It illustrates a concept that is becoming very important in medicine, which is the individualization of treatment. We have to individualize therapy based on the patient’s characteristics. It is important for the public to appreciate that one diet or one drug is not the optimal treatment for every patient."
Coffee drinkers in the United States consume an average of 3.1 cups each day. However, "if you only drink one cup each day, the results of our study probably have little relevance because at that level your daily coffee dose is relatively low," Mr. Superko said.
Mr. Superko said people concerned about increasing fatty acids and L.D.L. cholesterol should think twice about drinking a lot of decaffeinated coffee.
"But those who are overweight and have low levels of H.D.L.2 but normal levels of ApoB, might consider the potential benefit of drinking decaffeinated over caffeinated coffee," he said.
According to the American Heart Association, whether high caffeine intake increases the risk of coronary heart disease is still under study, however moderate coffee drinking — 1-2 cups per day — doesn’t seem to be harmful.
Peter D. Wood, Ph.D., co-authored the study, which was funded by the National Institutes of Health.