For the millions of people who depend on coffee to jumpstart their day, cholesterol is probably the last thing on their mind as they wait for the morning jolt of caffeine to kick in. In the past few years, though, more and more evidence hints that coffee can increase cholesterol levels.

Experts say that the majority of coffee-drinking Americans do not need to worry about the impact of a cup of joe on cholesterol levels. That's because most Americans drink filtered coffee, which is believed to have much less of an effect on cholesterol than unfiltered coffee. Filters seem to remove most of the cholesterol-boosting substances found in coffee.

But a cholesterol check may be in order for people who use a French press or percolator to make their coffee or who prefer espresso or other varieties of unfiltered coffee, according to Dr. Michael J. Klag, the vice dean for clinical investigation at Johns Hopkins University School of Medicine in Baltimore.

In 2001, Klag and his colleagues reviewed more than a dozen studies that looked at the relationship between coffee consumption and cholesterol levels. They found that drinking an average of six cups of coffee a day was associated with increased total cholesterol and LDL, the harmful type of cholesterol. Nearly all of the rise in cholesterol was linked to unfiltered coffee.

The coffee culprit

Although caffeine is often cast as a villain, the stimulant is not to blame for unfiltered coffee's effect on cholesterol levels. According to Klag, the increase in cholesterol is believed to be caused by oils called terpenes that are found in coffee, but are mostly removed by filters.

"Persons who drink unfiltered coffee should get their cholesterol checked to make sure it is not elevated," says Klag.

The Johns Hopkins researcher notes that in a 1994 study he and his colleagues found an association between coffee consumption and an increased risk of heart disease. But most of the increased risk was linked to coffee drinking before 1975. It was during the mid-1970s, Klag points out, that drip coffee makers became widely used in the United States, making filtered coffee the norm.

Although Klag advises his patients who drink unfiltered coffee to switch to filtered brew, he says that not everyone needs to be overly concerned about the effect of unfiltered coffee on cholesterol. He notes that cholesterol levels are a "combination of how you live, what you eat and what genes you inherit." A healthy person with low cholesterol probably does not need to worry too much about the effect of coffee on cholesterol levels, he says.

A Dutch researcher who has also documented the cholesterol-boosting effect of unfiltered coffee agrees that the risks need to be seen in perspective.

"Unfiltered coffee has much less effect on your heart disease risk than smoking, high blood pressure or being overweight," says Dr. Martijn B. Katan, a professor at the Wageningen Center for Food Sciences and Wageningen University. "But if you want to optimize your cholesterol levels, you should avoid large daily amounts of unfiltered coffee."

Unfiltered coffee seems to boost cholesterol the most, although a handful of recent studies hint that filtered coffee may have an effect on cholesterol, too. In one study, researchers in Sweden found that people who normally drank filtered coffee experienced a small drop in cholesterol levels when they stopped drinking coffee for a few weeks. The results were "surprising," according to Dr. Elisabeth Strandhagen, of Sahlgrenska University Hospital(CK) in Goteborg, who led the study.

"We have done some tests on coffee filters, but we cannot explain why the filtered coffee had this effect on serum cholesterol," she says.

Despite the findings, filtered coffee seems to have a much smaller effect on cholesterol than unfiltered coffee. Strandhagen encourages people with high cholesterol or who are at high risk of heart disease to choose filtered coffee. They should also avoid coffee filters that have "aroma holes," which are very common in Sweden, she says.

Pieces of the puzzle

But filtered vs. unfiltered may not be the most important question to ask about coffee and cholesterol, according to a spokesperson for the American Dietetic Association.

"People try to pin a culprit" when it comes to coffee and cholesterol, "but people do not live in an isolated world," says Dr. Gail C. Frank, a professor of nutrition in the department of family and consumer sciences at California State University Long Beach. According to Frank, there are "several pieces to the coffee story," including not only whether people drink filtered or unfiltered coffee, but how much they drink and what they are doing besides drinking coffee‹such as smoking.

While unfiltered coffee may contain substances that raise cholesterol levels, many popular coffee drinks sold at coffee houses seem more like desserts than beverages to Frank. The "bolts" of cream and sugary calories raise questions of their own about coffee's effect on cholesterol, she says.

When making decisions about coffee, Frank encourages people not to look for a yes or no answer. It's not a simple question of "do drink coffee" or "don't drink coffee," she says.

Instead, Frank encourages people to "filter through" their own lives and their own cardiovascular risk factors to make a decision about how much and what type of coffee to drink.

Merritt McKinney is a health writer based in Houston.