Understanding Cholesterol

Understanding Cholesterol


Cholesterol is a wax-like substance that plays a crucial role in the human body.1 It is an integral part of every cellular membrane and is a precursor to various hormones. Cholesterol is naturally lipophilic, meaning it dissolves and is attracted to fats instead of water.2 As such, cholesterol is carried through the bloodstream as “lipoproteins” after being packed together with proteins.

The five main types of lipoproteins are: 1) chylomicrons; 2) very low-density lipoprotein (VLDL); 3) intermediate-density lipoprotein (IDL); 4) low-density lipoprotein (LDL); and 5) high-density lipoprotein (HDL).3 LDL and HDL cholesterols are often the topics of discussions concerning the impact of cholesterols on human health. In addition, triglycerides, a type of non-cholesterol lipid molecule in the body, are also often an interest when evaluating blood lipid levels.4

LDL (Bad) Cholesterol 

LDL cholesterols are often known as the “bad” cholesterol because of the role they play in atherosclerosis, a process of arteries hardening from the build-up of cholesterol plaques.5 Atherosclerosis is a risk factor for the development of atherosclerotic cardiovascular diseases (ASCVDs), which include heart diseases such as coronary heart disease, peripheral arterial disease, and cerebrovascular disease.5 As such, high levels of LDL cholesterol – also known as hypercholesterolemia – should be avoided for heart health.6

The standard LDL cholesterol levels according to the Adult Treatment Panel (ATP) III are as follows:7


<100 mg/dL

Above Optimal

100-129 mg/dL

Borderline High

130-159 mg/dL


160-189 mg/dL

Very High

>190 mg/dL


HDL (Good) Cholesterol

HDL cholesterols are often known as the “good” cholesterol because of their cardioprotective property.4 They play a role in transporting cholesterol from the rest of the body back to the liver where it is removed. As such, higher levels of HDL cholesterol are known to prevent atherosclerosis.

The standard HDL cholesterol levels according to ATP III are as follows:7


<40 mg/dL


>60 mg/dL



Triglycerides, like LDL cholesterols, do not carry a great reputation. High levels of triglycerides are associated with increased risk of ASCVDs.8 Even though triglyceride molecules themselves are not usually found in atherosclerotic plaques in arteries, having high levels of triglycerides (hypertriglyceridemia) is often associated with high levels of atherogenic cholesterols such as LDL cholesterol. Triglyceride levels vary greatly based on food intake and thus testing should be done after fasting.

The standard fasting triglyceride levels according to ATP III are as follows:7


<150 mg/dL

Mild Hypertriglyceridemia

150-499 mg/dL

Moderate Hypertriglyceridemia

500-886 mg/dL

Very High or Severe Hypertriglyceridemia

>866 mg/dL



Heart Health – Dyslipidemia, or the imbalance of cholesterol levels, is known to be a major risk factor for the development of cardiovascular diseases (CVDs) by promoting plaque build-up in the arteries.9 When plaques build up, the arteries harden and narrow, which can subsequently be blocked and lead to ASCVDs and stroke.10 Elevated levels of LDL cholesterol and triglycerides in the bloodstream are especially known to increase the risk of ASCVDs.9

Diabetes – Diabetes mellitus is known to be associated with an increased risk of atherosclerosis and CVDs.11 It is thought that obesity and insulin resistance often precede the clinical diagnosis of type 2 diabetes mellitus, both of which are associated with hypertension and dyslipidemia, risk factors for CVDs. Hypertriglyceridemia is common in diabetes, and it is thought that insulin resistance promotes biochemical processes that favor the release of triglycerides in the bloodstream.

1. Huff T, Boyd B, Jialal I. Physiology, Cholesterol. In: StatPearls. StatPearls Publishing; 2023. Accessed July 12, 2023. http://www.ncbi.nlm.nih.gov/books/NBK470561/
2. Craig M, Yarrarapu SNS, Dimri M. Biochemistry, Cholesterol. In: StatPearls. StatPearls Publishing; 2023. Accessed July 12, 2023. http://www.ncbi.nlm.nih.gov/books/NBK513326/
3. Lee Y, Siddiqui WJ. Cholesterol Levels. In: StatPearls. StatPearls Publishing; 2023. Accessed July 12, 2023. http://www.ncbi.nlm.nih.gov/books/NBK542294/
4. Ahmed S, Shah P, Ahmed O. Biochemistry, Lipids. In: StatPearls. StatPearls Publishing; 2023. Accessed July 12, 2023. http://www.ncbi.nlm.nih.gov/books/NBK525952/
5. ElSayed NA, Aleppo G, Aroda VR, et al. 10. Cardiovascular Disease and Risk Management: Standards of Care in Diabetes—2023. Diabetes Care. 2022;46(Supplement_1):S158-S190. doi:10.2337/dc23-S010
6. Ibrahim MA, Asuka E, Jialal I. Hypercholesterolemia. In: StatPearls. StatPearls Publishing; 2023. Accessed July 12, 2023. http://www.ncbi.nlm.nih.gov/books/NBK459188/
7. Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive Summary of The Third Report of The National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, And Treatment of High Blood Cholesterol In Adults (Adult Treatment Panel III). JAMA. 2001;285(19):2486-2497. doi:10.1001/jama.285.19.2486
8. Karanchi H, Muppidi V, Wyne K. Hypertriglyceridemia. In: StatPearls. StatPearls Publishing; 2023. Accessed July 12, 2023. http://www.ncbi.nlm.nih.gov/books/NBK459368/
9. Du Z, Qin Y. Dyslipidemia and Cardiovascular Disease: Current Knowledge, Existing Challenges, and New Opportunities for Management Strategies. J Clin Med. 2023;12(1):363. doi:10.3390/jcm12010363
10. Kopin L, Lowenstein C. Dyslipidemia. Ann Intern Med. 2017;167(11):ITC81-ITC96. doi:10.7326/AITC201712050
11. Schofield JD, Liu Y, Rao-Balakrishna P, Malik RA, Soran H. Diabetes Dyslipidemia. Diabetes Ther. 2016;7(2):203-219. doi:10.1007/s13300-016-0167-x



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