High-density lipoprotein cholesterol or HDL cholesterol is a particle composed of a lipoprotein that surrounds a lipid molecule called cholesterol. Remember that not all cholesterols are bad. HDL cholesterol has also been referred to as the “good cholesterol” due to its positive roles in the human body and its specific benefits in promoting cardiovascular health.
What Is Good About HDL Cholesterol: The Roles and Health Benefits of Good Cholesterol
For starters, cholesterol is a molecule minimally soluble in water. It is a fundamental structural component of all animal cell membranes, and an important precursor for the biosynthesis of steroid hormones, bile acid, and vitamin D. Lipoproteins such as high-density lipoprotein or HDL serves as the transporters of hydrophobic molecules in water such as cholesterol. HDL cholesterol is essentially a cholesterol surrounded by a lipoprotein.
The role of HDL cholesterol centers primarily on picking up excess cholesterol in tissues and the bloodstream to take it back to the liver where it is broken down and either reprocessed or removed from the body. The process is called reverse cholesterol transport, and this function confers benefits to cardiovascular and overall health.
Excessive cholesterol levels in the bloodstream have been linked to cardiovascular disease. To be specific, high levels of bad cholesterol or low-density lipoprotein cholesterol in the bloodstreams lead to a buildup of a plaque in the arteries. This buildup would eventually lead to a disease called atherosclerosis in which the arteries are hardened and narrowed, thus limiting the flow of oxygen-rich blood and overworking the hearth to compensate for the restricted blood flow.
Atherosclerosis has no initial general symptoms. However, extreme cases of this disease and depending on the affected arteries could lead to more severe diseases such as coronary artery disease, stroke, peripheral artery disease, and kidney problems.
Several studies have reported that reasonable levels of HDL cholesterol in the bloodstream provide benefits to cardiovascular health because of its role in managing excessive levels LDL cholesterol in the blood. The separate studies of G. Assmann and A. M. Gotto, and P. Barter explained that HDL cholesterol prevents atherosclerosis directly and indirectly by removing cholesterol from foam cells, inhibiting the oxidation of LDL, and by limiting the inflammatory processes that underlie atherosclerosis.
However, the book chapter by Maryse Guerin that reviewed relevant literature mentioned that despite observational studies indicating an inverse relationship between HDL cholesterol levels and risk of developing atherosclerosis, there are still doubts about the overall role of reverse cholesterol transport. This doubt stems from the fact that the use of drugs intended to raise HDL cholesterol levels has failed to lower the risk and prevent the development of atherosclerosis.
Note that other studies have revealed that even in people with naturally high levels of HDL or those who increase their HDL levels through diet and physical activity, the risks of developing atherosclerosis and cardiovascular disease remain present. These findings are indicative of other factors or variables at play in the development and progression of atherosclerosis.
A mathematical model presented in the study of W. Hao and A. Friedman noted that people with LDL above 190 mg/dL and HDL below 40 mg/dL in their bloodstream are at high risk of developing atherosclerosis. On the other hand, people with LDL below 100 mg/dL and HDL above 50 mg/dL are at no risk. Their model further integrated key variables apart from LDL and HDL ratio to include free radicals and oxidized LDL, MMP and TIMP, and other cells such as immune cells, smooth muscle cells, and foam cells. Nevertheless, the study argued that the mathematical model provides a better assessment tool for determining atherosclerosis risk.
Take Away: The Roles and Benefits of HDL Cholesterol in the Body
HDL cholesterol is generally referred to as the good cholesterol because of their beneficial roles or functions in the human body. The discussion above noted that cholesterol has fundamental functions in the structuring of cellular membranes and the biosynthesis of steroid hormones, bile acid, and vitamin D.
The specific health benefits of HDL cholesterol stems from its role in transporting excessive cholesterol from tissues and bloodstream and back to the liver for reprocessing or excretion. This function plays a role in preventing the buildup of plaque in the arteries that could lead to atherosclerosis and more severe diseases such as cardiovascular problems and organ failure.
HDL cholesterol further prevents or manages atherosclerosis by removing cholesterol buildup from plaques, as well as by preventing the oxidation of cholesterol or regulating the inflammatory process that both play a role in plaque buildup.
FURTHER READINGS AND REFERENCES
- Assmann, G. and Gotto, A. M. 2004. “HDL Cholesterol and Protective Factors in Atherosclerosis.” Circulation. 109(23). DOI: 10.1161/01.CIR.0000131512.50667.46
- Barter, P. 2005. “The Role of HDL Cholesterol in Preventing Atherosclerotic Disease.” European Heart Journal Supplements. 7(1): F4-F8. DOI: 10.1093/eurheartj/sui036
- Guerin, M. 2017. “Reverse Cholesterol Transport in HDL Metabolism: Relevant to Atherosclerosis Progression and Cardiovascular Diseases.” In ed. T. Komoda, The HDL Handbook: Biological Functions and Clinical Implications. 3rd ed. London: Academic Press. DOI: 10.1016/B978-0-12-812513-7.00005-7
- Hao, W. and Friedman, A. 2014. “The LDL-HDL Profile Determines the Risk of Atherosclerosis: A Mathematical Model.” PLoS ONE. 9(3): e90497. DOI: 10.1371/journal.pone.0090497
