Having high blood levels of “bad” (LDL) cholesterol predicts increased risk for heart attacks, but contrary to what we thought in the past, having high levels of “good” (HDL) cholesterol does not necessarily predict protection from heart disease.
A recent report from the Copenhagen General Population Study shows that having either low or high levels of HDL cholesterol also predicts increased risk for infections such as gastroenteritis and bacterial pneumonia (European Heart Journal, December 8, 2017).
Having a low HDL cholesterol (<30) predicts a 21 percent increased risk for infections, and having a high HDL (>100) predicts an eight percent increased risk. Nine percent of almost 100,000 people followed for six years were hospitalized for serious infections. Having an HDL greater than 100 or below 30 was associated with increased risk for a bacterial infection, while having only a low HDL-C level was associated with viral infections. The authors found the same increased risk for infections from low HDL levels when they reviewed almost 10,000 charts from the Copenhagen City Heart Study.
Another study that followed more than 600,000 people showed that having low levels (<30) of HDL cholesterol predicts increased risk for a premature death from heart attacks, cancers and other causes, while having high blood levels of HDL (>90) was associated with significantly increased rate of deaths from heart attacks (J Am Coll Cardiol, 2016;68(19):2073-2083). The death rate was lowest in those with HDL levels between 51 and 70.
How Both Low and High HDL May Increase Risk for Infections
The Framingham study showed that people with low blood levels of the good HDL cholesterol and high levels of triglycerides are the ones most likely to suffer from heart attacks (JAMA, 1984:251(3):365-374). HDL helps to remove excess triglycerides from the bloodstream by carrying them to the liver, where the fat is incorporated into bile, which then passes from your gall bladder and out of your body.
In a like manner, HDL also carries harmful bacterial toxins from the bloodstream to be disposed in bile also. People who have low levels of HDL lose at least part of their ability to clear bacterial toxins from their bodies. Those who have very high blood levels of HDL may have defective HDL that cannot do its job of removing bacterial toxins, therefore increasing risk for infections.
The Takeaways from These Studies
- LDL cholesterol levels over 100 predict increased risk for heart attacks.
- HDL levels should not be used to predict protection from heart attacks.
- HDL levels below 30 and above 90 may predict increased risk for heart attacks. They may also predict increased risk for infections. If your HDL falls in these ranges, your doctor may want to search for hidden infections.
- Sugar and other refined carbohydrates can cause high rises in blood sugar that raise triglycerides. High triglycerides can cause HDL to drop and increase risk for diabetes, heart attacks and premature death.
- Lifestyle changes can lower LDL, raise HDL and help to prevent heart attacks and other causes of premature death.
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.