High cholesterol puts you at greater risk for heart disease, the number one killer of women and men in America, notes the Centers of Disease Control and Prevention. This makes cholesterol testing especially important. Eating before certain types of cholesterol testing is fine, but can skew other types of cholesterol tests. Doctors often recommend a lipoprotein lipid test for the most complete cholesterol profile. This requires fasting because eating before the test results in unreliable cholesterol readings.
Cholesterol Basics
Cholesterol moves through the bloodstream carried by lipoproteins. Low-density lipoprotein, or LDL, helps to deposit cholesterol along the inner lining of arteries. This can cause the arteries to narrow and negatively affect blood flow. High-density lipoprotein, or HDL, cholesterol helps to remove cholesterol from artery linings and deposits it in the liver for removal. Triglycerides are not a form of cholesterol, but are another type of lipid often measured with cholesterol; high triglyceride levels commonly associate with high LDL.
Cholesterol Testing and Eating
A cholesterol test simply requires a blood draw. The lab work ordered by your doctor to evaluate this blood sample can differ, however. If measuring total cholesterol count alone, what you ate before blood testing won't matter. Total cholesterol levels don't vary based on food consumed beforehand. Similarly, if your doctor orders readings for total cholesterol and HDL, what you ate before testing will do little to affect results. Alternatively, if your doctor orders cholesterol testing to measure LDL or triglycerides, eating beforehand will skew the measurements. A complete lipoprotein profile includes measurements for LDL and triglycerides, as well as HDL and total cholesterol, so fasting is a requirement before this test.
Fasting Recommendations
Doctors recommend fasting for nine to 12 hours before lipoprotein profile cholesterol testing. The does not allow food, beverages and medications during this time, but permits drinking water. Eating before blood testing can cause triglyceride levels to rise by 20 to 30 percent. This would affect calculation measurements for LDL, too, resulting in unreliable readings. Alcohol consumption also causes triglycerides to rise dramatically. It is best not to drink alcohol within 24 hours before testing.
Assessing Cholesterol Testing
Cholesterol testing that only measures total cholesterol and HDL has its merits, but is only a screening test. A more accurate and complete picture of cholesterol comes from the lipoprotein profile test, which requires a preceding fast. The National Cholesterol Education Program recommends a complete lipoprotein test for patients, rather than the screening. The program also recommends a complete lipoprotein profile for adults 20 years and older once every five years. For optimal health, total cholesterol levels should fall below 200 mg/dL, below 100 mg/dL for LDL, below 150 mg/dL for triglycerides and above 40 mg/dL for HDL.
References
- Harvard Health Publications; Which Cholesterol Test Should You Get?;
- Lab Tests Online; Cholesterol
- National Cholesterol Education Program; Third Report of the Expert Panel on Detection, Evaluation, and Treatment of the High Blood Cholesterol in Adults (Adult Treatment Panel III): Executive Summary; 2001
- Centers for Disease Control and Prevention; Heart Disease Facts; April 2011
