DALLAS – Fresh questions are percolating about the health effects of coffee, this time the decaffeinated variety.

One of the first substantial studies to test it like a drug instead of just asking people how much of it they consumed found higher blood levels of cholesterol-precursor fats in those drinking decaf vs. regular coffee or none at all.

But the differences were very small, especially when compared with the effects of, say, the doughnut that might be dunked into the brew.

“I don’t think there’s a health threat,” regardless of which type of coffee is consumed, said Dr. H. Robert Superko of Fuqua Heart Center in Atlanta, who did the study when previously at Stanford University. He reported on it Wednesday at an American Heart Association conference.

It was one of the few coffee studies not funded by industry – federal taxpayers picked up the more than $1 million tab. (If you think that’s a lot of money, consider that more than half of Americans drink three cups or more a day).

Participants were given Mr. Coffee machines, premeasured bags of Maxwell House, and periodic blood tests so scientists could tell just how much caffeine and coffee they had consumed over eight weeks.

The 187 volunteers were put into three groups: no coffee, 3 to 6 cups a day of regular, or 3 to 6 cups of decaf. Coffee was consumed black, no cream or sugar. Diet surveys were taken for a week at the beginning and the end so researchers could evaluate whether changes in eating habits might have affected results.

The result: Decaf drinkers had modestly higher levels – 8 to 18 percent – of fatty acids and precursors of LDL or bad cholesterol than the others.

Nobody knows why, but Superko has some guesses. Fats give coffee flavor, and a more flavorful species of beans, robusta, is commonly used for decaf to make up for the flavonoids and other ingredients that are lost during the decaffeination process. Regular coffee uses a different bean, arabica.

However, several experts were skeptical of the whole thing.

“That’s interesting, but it would not affect my recommendations to patients,” said Dr. Donald Lavan, a cardiologist at the University of Pennsylvania and a heart association spokesman.

“This whole area of coffee and heart disease has been brewing with inconsistent evidence of harmful effect,” said Dr. Lawrence Appel of Johns Hopkins School of Medicine.

Dr. Ronald Krauss, a nutrition expert from the University of California at Berkeley who is on the heart association’s board of directors, said the theory needed testing in a bigger study. Until then, this one “should not be the basis for making any recommendations to the public,” he said.