For years we've been told we need to fast for eight to 12 hours before getting a blood test to measure our cholesterol. But for the second time in two years, a large study finds there's no evidence that fasting is necessary.
"The evidence on which the fasting recommendation is based is weak at best," said senior author and cardiologist Sripal Bangalore of New York University Langone Medical Center. "Our study and data from other studies now really question this practice," he told AARP in an email, adding that unless research can be done disproving the new results, "we should abandon the requirement for fasting."
In the study, Bangalore and his colleagues analyzed cholesterol-test readings, called blood lipid panels, from more than 16,000 adults enrolled in a federal health and nutrition survey. About 10,000 of the readings were from those who had fasted more than eight hours, while the rest were non-fasting readings.
The researchers then followed the subjects for about 14 years to see if fasting or non-fasting results were better predictors of death from either heart disease or other causes. The result, they found, was basically no difference between the two.
The trouble with fasting, said Bangalore, is that it means doctors are testing patients' blood when they're on their "best behavior," he told Medscape. "We tell them, 'Don't eat your french fries for eight hours and then we'll take your lipid panel.' But that's not what the body is exposed to the majority of the time." It makes more sense to measure the blood when patients have had a normal meal.
The study is not the first to question the value of fasting before a cholesterol test. A Canadian study of more than 200,000 people in 2012, published in JAMA Internal Medicine, also found that fasting had little impact on cholesterol-test results. "F asting for routine lipid levels is largely unnecessary," the researchers concluded.
From the patients' point of view, fasting is also inconvenient. Plus, if patients forget to fast, the doctor often makes them reschedule the test, which can delay diagnosis and treatment, Bangalore said. "Non-fasting is more convenient to the patients and perhaps more accurately reflects [their] true lipid profile, " he adds.
The study was published online August 12 in the journal Circulation.
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