High-density lipoprotein (HDL) is an important large molecule found in the human body. Generally, HDL is also known as the “good cholesterol,” but how it can significantly affect people’s health and well-being is usually overlooked. HDL is important because it regulates and/or reduces the amount of fats and cholesterol through transportation and metabolism.
Some features of HDL
HDL is a spherical-shaped complex with two distinct layers.
The inner layer (or core) consists of cholesterol esters and triglycerides (TG) while the outer layer consists of apolipoprotein, cholesterol, and phospholipid.
Its main function is absorbing and transporting fatty acids and cholesterol from peripheral tissues to the liver.
HDL is also known to reduce oxidative stress, inflammation, and contain anti-atherogenic (preventing fatty acid build up in arteries) potential.
In contrast to HDL, low density lipoprotein (LDL, also known as “Bad Cholesterol”) transports cholesterol and fatty acids from the liver to peripheral tissues (Donnan, G.A. et al).
Benefits of higher HDL levels
Watanabe, J. et al and Zhang, Y. et al studied how levels of HDL are associated with stroke in Asian populations. In Japan, Jichi Medical School studied 11,027 patients (4,284 men and 6,743 women), measuring patients’ HDL concentrations and stroke events during annual follow-ups. The study persisted with a mean average time of 10.7 years. Within that time frame, 412 stroke events occurred; 51 subarachnoid hemorrhoids (SAH), 95 intracerebral hemorrhage (ICH), 266 cerebral infarction (CI), and 177 other stroke subtypes. Regression models were used to measure the hazard ratio (HR) of patients of low, medium, and high HDL concentrations and the stroke subtypes.
The hazard ratio used to measure how often (probability) a specific event occurs when two groups are compared (usually a control group and treatment group)
It was found that high HDL levels can decrease the risk of stroke in Japanese men and women combined, but especially in women suggesting that the benefit is better for women (Watanabe, J. et al, 2020).
High levels of HDL were associated with the decreased incidence of intracerebral hemorrhage in women independent of the other traditional risk factors (Watanabe, J. et al, 2020).
Moderate HDL levels were associated with a decreased risk of atherothrombotic cerebral infarction.
Zhang, Y. et al studied the associations of HDL with first ischemic stroke in a Chinese hypertensive population in two different cities: Lianyungang and Rongcheng, China. The study consists of 2,462 patients with identified first ischemic stroke and 2,463 patients with no IS as controls.
Chi square tests showed that HDL levels greater than or equal to 65.4 mg/dL provided a protective effect against the first ischemic stroke, higher levels of LDL were significant in causing adverse effects of ischemic stroke.
Key takeaway: Increased HDL levels can decrease the risk of stroke as well as other diseases such as cardiovascular diseases.
Why high levels of LDL are not desirable?
LDL levels below 100 mg/dL is recommended to reduce the risk of cardiovascular diseases. Cholesterol itself is not “bad” as it is required to make important hormones, vitamin D and protect nerves. However, high levels of LDL cholesterol results in this cholesterol binding to the walls of our blood vessels forming plaques.
Plaques reduces blood flow and increase the risk of cardiovascular disease (CVD). Since LDL cholesterol is the major type of cholesterol in your body it is important to keep levels of this cholesterol lower than 100 mg/dL.
How do you raise HDL levels and lower LDL levels?
According to the Centers of Disease Cohttps://www.cdc.gov/cholesterol/prevention.htm
ntrol and Prevention (CDC), there are three major ways to lower LDL levels:
diet
exercising
avoiding alcohol and smoking
The following foods are good options to decrease LDL and increase HDL: whole grains, fruits, vegetables, oatmeal, beans, unsaturated fats, and olive oils. Some foods to avoid are: high fats, saturated fats, trans fats, high sugar, high salt, and tropical (palm) oils. Exercising is one of the best ways to increase HDL.
A typical adult should have at least 2 hours and 30 minutes worth of exercising per week. Exercising could be walking, bicycling, playing sports, and many other activities. Avoiding alcohol consumption and smoking will also lower the LDL levels. Drinking may elevate the amount of cholesterol and fats in the liver.
Eventually, high drinking levels can also cause liver damage, affecting liver metabolism and other essential pathways associated with the liver. Smoking can damage blood vessels, significantly increasing the risks for stroke and CVD.
Does having higher HDL levels guarantee you will be stroke-free?
Unfortunately, no. Having a HDL score higher than 60 mg/dL reduces your chance of getting stroke and other diseases, but some patients will still be susceptible to stroke and CVD. Nessler, K. et al found that patients with Type 2 diabetes actually have normal to high range of HDL levels. Hence, HDL level is only a snapshot of the bigger picture and does not make an individual completely invulnerable to stroke. Meaning, other essential macromolecules or molecules must also be accounted for when evaluating an individual.
Conclusion
High levels of HDL provide health benefits and reduces the risks for some diseases such as stroke and CVD. However, gender is another factor to consider of how HDL can decrease risks of disease. In some cases, HDL level may be a preventative measure in women, but not in males. In conclusion, increasing level of HDL above 60 mg/dL seems to be a good preventative step in decreasing the risk of strokes for you and your loved ones.
Written by Xong Vue and edited by Aldrin V. Gomes, PhD
REFERENCES:
Donnan, G.A., Fisher, M., Macleod, M., & Davis, S. M. (2008). Stroke. Lancet 371(9624):1612–23
Nessler, K., Windak, A., Grzybczak, R., Nessler, M. B., Siniarski, A., & Gajos, G. (2018). High-density lipoprotein (HDL) cholesterol – more complicated than we think. Annals of Agricultural and Environmental Medicine. Vol 25. No 3. 517–526.
Watanabe, J., Kakehi, E., Kotani, K., Kayaba, K., Nakamura, Y., and Ishikawa, S. (2020). High-Density Lipoprotein Cholesterol and Risk of Stroke Subtypes: Jichi Medical School Cohort Study. Asia Pacific Journal of Public Health. Vol. 32(1) 27–34.
Zhang, Y., Li, Y., Liu, C., Yu, H., Chen, C., Bi, C., Chongqian Fang, Ma, H., Li, A., Dong, Q., Liu, L., Wang, B., Huang, X., Cheng, X., Zalloua, P., Xu, X., Huo, Y., & Li, G. (2021). High-Density Lipoprotein Cholesterol and the Risk of First Ischemic Stroke in a Chinese Hypertensive Population. People’s Republic of China. Vol. 16 801–810.
Centers for Disease Control and Prevenetion (CDC) (2022). Preventing High Cholesterol.