OK To Eat Before Rolling Up Sleeve For Cholesterol Test?

Nov 13, 2012
Originally published on November 13, 2012 2:49 pm

Skipping breakfast to take a medical test is nobody's idea of fun. And it's one reason why many people never get around to having a cholesterol test.

So it's good news that some doctors are now saying that for most people, a nonfasting cholesterol test will do just fine.

But who gets to take a pass on the unpleasant skip-your-breakfast routine? To find out, Shots called Samia Mora. She's a cardiologist at Brigham and Women's Hospital, and an assistant professor at Harvard Medical School.

The bottom line: If you don't already have high triglycerides (more than 400 milligrams per deciliter of blood) and you're not diabetic, forget the fast. Enjoy your breakfast.

This seems so utterly different from what we've been told for so many years, we had to know more. Why diabetics? "Their triglycerides tend to be high," Mora says. And triglycerides are the blood lipids that shoot up after eating a fatty meal.

Still, Mora says, you'd have to eat a really fatty meal to move the triglyceride level much. "Steak and french fries within a couple of hours of your test" could do that, she says.

For most people, though, triglycerides aren't the most critical number. In recent years cardiologists have shifted to looking at the ratio of different fats in the blood rather than the individual numbers anyway.

So, for instance, your doctor might want to know the relationship between total cholesterol in your blood and HDL — the high-density lipoprotein that's the so-called good cholesterol.

That ratio tends not to shift very much, even right after eating. So some doctors have started questioning the need for the fasting cholesterol test, which in most cases requires a morning visit to a blood lab after skipping food for 9 to 12 hours.

Black coffee, thank goodness, is usually allowed. Still, the deprivation and inconvenience can discourage people from getting their cholesterol tested, and make it harder for doctors to follow up.

Some Canadian doctors decided to look at whether the fast makes a difference. They analyzed lab records of more than 200,000 people who had cholesterol tests in Calgary last year.

The people had eaten anywhere from one hour to 11 hours before the blood test. The relationship between total cholesterol and HDL changed very little based on fasting time, the researchers found..

The levels of low-density lipoprotein (or LDL, the so-called bad cholesterol), varied about 10 percent, and triglycerides varied about 20 percent.

The findings were published Monday in the Archives of Internal Medicine.

This is hardly the last word on cholesterol tests. In the Calgary study, most of the people had fasted for at least 9 hours, and the nonfasting people were younger and healthier. And although the U.S. Preventive Services Task Force says either non-fasting or fasting tests will do, most doctors still think of fasting tests as the gold standard.

Why's that? "We doctors like to have things standardized," Mora says, with a laugh. But she's already started changing her practice, telling patients they can eat or not, as they please. "If they just have a piece of toast and a cup of coffee, it's not going to change their results." Mora is unabashedly pro-breakfast; she co-wrote a commentary on the Archives study arguing that point.

If there's a cholesterol test in your future, talk with your doctor ahead of time about whether it's OK in his or her book to eat before your blood gets drawn.
