For many years HDL cholesterol has been called “good” because it carries plaque-forming particles from your arteries and bloodstream back to your liver, where they can be removed from your body. An exciting new study from Texas Medical Center shows that regular HDL cholesterol may not be very effective in doing this, but another form called Nascent HDL carries these protein-fats much more quickly to your liver to be removed from your circulation (Arteriosclerosis, Thrombosis, and Vascular Biology, Nov 21, 2017).
The Nascent HDL cholesterol goes directly to your liver and skips being converted to the mature form of HDL. It can clear plaque-forming particles from your arteries, and carry them to your liver, a thousand times faster than regular HDL does. It takes Nascent HDL less than two minutes to do this job, compared to the several days that HDL is thought to take.
For a long time, doctors have questioned the value of using HDL levels to predict heart attacks. A review of 15 studies shows that the risk for heart attacks does not vary directly with the concentration of HDL in your bloodstream (Lipids in Health and Disease, November 14, 2017).
Further evidence for the lack of effect of HDL itself from preventing heart attacks comes from studies on diabetics. Diabetics are at high risk for forming plaques that cause heart attacks because diabetes impairs the ability of (Nascent) HDL cholesterol to clear the bad LDL cholesterol from your arteries (Cardiovasc Diabetol, 2017 Oct 12;16(1):132).
Tests for levels of Nascent HDL are not yet available in commercial laboratories. Some of the Nascent HDL eventually forms HDL, so a test for regular HDL may sometimes predict the amount you have of this newly identified “good” Nascent HDL. However, some people with very high blood HDL levels are at increased risk for heart attacks because their protective Nascent HDL is converted so fast to regular HDL that they lose the benefit of the Nascent HDL protecting them from forming plaques in their arteries.
Current Cholesterol Guidelines
LDL cholesterol is considered to be “bad” because in its oxidized form, it carries certain particles into the inner linings of arteries to form plaques. Today, if your bad LDL cholesterol is greater than 100, your doctor will prescribe lifestyle changes and probably drugs to help prevent a heart attack – even if your “good” HDL is high.
People with high levels of the bad LDL cholesterol are at increased risk for suffering heart attacks, even if they have high levels of the good HDL cholesterol, and in some people, very high levels of HDL cholesterol are associated with increased risk for heart attacks. In the future, scientists may develop drugs and lifestyle changes to raise blood levels of Nascent HDL. None of the current drugs that can raise HDL have been shown to reduce risk for heart attacks.
Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe’s full bio.