Heart Health: HDLs Not the Final Answer
By Nadine Salmon, BSN, IBCLC, Clinical Content Specialist AMN Healthcare
An important finding from a recent study in Denmark was released that may change the way we view High Density Lipoproteins (HDLs) or healthy lipids.
Historically, the medical community has always maintained the belief that HDL cholesterol levels are inversely related to the risk of ischemic cardiovascular disease. In other words, high HDL levels were thought to be protective against heart disease. Yet this new study questions whether this is in fact true, and suggests that low HDL cholesterol levels alone may not cause myocardial infarction (Haase, et al., 2011).
Scientists analyzed data on nearly 70,000 people in Denmark to affirm the link between low levels of HDL and increased heart attack risk in the general population. Interestingly, they discovered that in people with a certain gene mutation that lowers HDL, heart attack risk is not increased at all (Haase, et al., 2011).
The results of this study, published in The Journal of Clinical Endocrinology & Metabolism, indicate that simply having low HDL will not, in itself, raise the likelihood of a heart attack; other risk factors that can lead to heart disease, such as smoking, hypertension, diabetes and obesity, should also be considered. That said, it is extremely difficult to study good cholesterol without isolating additional risk factors. In an effort to isolate the effects of HDL itself, the Danish scientists focused on people with a well-known variant of a gene called LCAT, which lowers HDL levels, and occurs in about 4% of the population (Haase, et al., 2011). This variant gene is used as a stand-in for low HDL. However, those with the variant don't necessarily have the other risk factors that normally affect HDL levels in the larger population (Haase, et al., 2011).
In the study, researchers observed a 13% decrease in HDL relative to average levels, not caused by the gene variant. For people with the variant gene, the same HDL reduction was not linked to any increased risk of heart attack. These findings correlate with earlier research that demonstrated two other HDL-lowering genetic variants were NOT associated with an increased risk of heart disease.
This debate is particularly important because there are currently drugs in clinical trials that are designed to raise HDL cholesterol. Yet, if low HDL is not a cause of heart attacks, raising HDL may not be protective after all (Haase, et al., 2011).
However, until scientists really understand the interplay of HDL and LDL cholesterol on patients at cardiac risk, it is important that healthcare professionals continue to deliver the message that HDL cholesterol is beneficial and can be raised by good nutrition and increased exercise.
Haase, C. et al. (2011). LCAT, HDL Cholesterol and Ischemic Cardiovascular Disease: A Mendelian Randomization Study of HDL Cholesterol in 54,500 Individuals. JCEM [The Journal of Clinical Endocrinology & Metabolism]. Retrieved from: http://jcem.endojournals.org/content/early/2011/11/10/jc.2011-1846
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