What is cholesterol?
Cholesterol is a kind of lipid (fat), which is important for your body. It has several essential biological functions. Your body gets some cholesterol from food but also makes as much as it needs. It’s present in many foods of animal origin, but not in those of plant origin.
Cholesterol is feared for its association with heart disease. But, in recent years, the understanding of how cholesterol in food works has changed. Cholesterol from food is thought to not be directly linked to the levels of cholesterol in your blood anymore.
In one day, an average adult consumes about 300 milligrams of cholesterol through food and creates 1 gram of it in their body, mainly in the liver. Your body controls your blood level by managing cholesterol manufacture in the liver.
Cholesterol is a biological molecule with several vital functions in your body. Every cell in the body needs it.
Your body uses cholesterol for many important functions and processes, including:
- It’s an essential component of cell membranes and organelles like mitochondria.
- 7-Dehydrocholesterol, which forms during the creation of cholesterol, may also be used by your body to make vitamin D.
- Your adrenal glands need cholesterol to form adrenal hormones.
- Sex hormones are also made with cholesterol as the base.
- Your liver uses cholesterol to make bile acids, which are needed for digestion.
Cholesterol is necessary for the structure of every cell in your body and a number of biological processes. For example, hormones like progestagens, androgens, estrogens, mineralocorticoids, and glucocorticoids are created using cholesterol or its precursors (i.e., substances from which cholesterol forms) as raw material.
Most of the cholesterol is used for the creation of bile acids, but the body efficiently recycles bile acids to get back cholesterol, if needed. So, medicines that prevent bile acid recycling can reduce cholesterol in the body.
Cholesterol is mainly created, absorbed, and removed by your liver, but your intestinal cells may also make some cholesterol.
Cholesterol from food
Your body creates 70% of the cholesterol it requires and absorbs the remaining 30% from the food you eat.
So, how much cholesterol you eat has only a marginal effect on your blood cholesterol levels. That is, your body regulates how much cholesterol it absorbs from food.
If your daily diet contains 300 milligrams of cholesterol, your intestinal cells absorb 40% to 60% of it. But if you eat 2 or 3 grams of cholesterol a day, they absorb only 10% of it.
Cholesterol in your food doesn’t affect your blood cholesterol directly, but foods that are rich in cholesterol also have a lot of saturated acids. These lead to a rise in blood cholesterol.
Most animal-origin foods are rich in cholesterol and saturated fats. Examples of these foods include dairy products (butter, ghee, cheese, cream, etc.), meat and meat products (lard, processed meats, etc.), and foods cakes, biscuits, and pastries.
Cholesterol is an insoluble molecule that needs chylomicrons and lipoproteins to carry it to the places it’s required in your body.
Low-density lipoproteins (LDL)
Cholesterol circulates in the blood as LDL, very low-density lipoproteins (VLDL), and other molecules — called non-high-density lipoproteins (non-HDL) — for uptake and use by your cells. If all cells in your are overloaded with LDL, they build up in your blood, leading to high blood levels of LDL. As a result, LDL get deposited on the walls of your arteries, forming artery plaques and causing heart disease.
High-density lipoproteins (HDL)
HDL are formed in the liver and intestinal cells. They collect excessive cholesterol from your tissues and blood, so they prevent artery plaque formation and protect against heart disease.
Low levels of HDL (less than 40 milligrams per deciliter) — which puts you at high risk for heart attack — are part of the metabolic syndrome that also includes obesity, hypertension (high blood pressure), dyslipidemia (abnormal blood cholesterol and triglyceride levels), and insulin resistance (type 2 diabetes mellitus).
Heart disease and cholesterol
Heart disease is caused by atherosclerosis, a disorder of blood vessel walls. Some damage to the lining of the arteries causes white blood cells to gather there. They collect excessive circulating LDL and deposit cholesterol in the artery walls.
The resulting inflammation forms a fibrous structure with lipids inside. When this structure grows, it narrows the artery and then bursts if it’s not treated in time.
The collection of cholesterol in the walls of your blood vessels is called plaque. As the plaques grow, the vessel becomes narrower, which restricts blood flow. Blockage of blood flow to the heart can cause angina (chest pain) or a heart attack.
What causes high cholesterol?
Your body has multiple checks and balances to manage your blood cholesterol levels — absorption from your food is controlled, whereas cholesterol formation in the liver is regulated based on your body’s cholesterol. This control is important because high blood cholesterol levels are associated with heart disease. High blood cholesterol is caused by:
Is cholesterol in food not important?
Multiple biofeedback methods regulate cholesterol levels in your blood. If you eat a lot of foods that contain cholesterol, cholesterol absorption by the intestines decreases. The liver controls your body’s cholesterol by making less and removing more cholesterol as bile acids. When these mechanisms work well, your blood cholesterol levels stay within healthy limits.
Though dietary cholesterol itself is not important, foods high in cholesterol are also high in saturated fats. Saturated fat consumption is associated with a rise in blood cholesterol.
Your body can make all the cholesterol it needs, so there’s no need for you to consume a lot of it through your food. By reducing your consumption of foods high in cholesterol and saturated fats, you can help reduce your blood cholesterol levels. So, try to eat more foods naturally high in fiber and unsaturated fats.
Ahern, K., Rajagopal, I. Biochemistry Free & Easy, Oregon State University, 2021.
British Heart Foundation: "High Cholesterol - Causes, Symptoms & Treatments."
Centers for Disease Control and Prevention: "About Cholesterol," "Cholesterol Myths and Facts."
Frontiers in Cell and Developmental Biology: "Cholesterol Metabolism: A Double-Edged Sword in Hepatocellular Carcinoma."
Frontiers in Pharmacology: "The role of cholesterol metabolism and cholesterol transport in carcinogenesis: a review of scientific findings, relevant to future cancer therapeutics."
Journal of Clinical Pathology: "Cholesterol metabolism."
The Medical Biochemistry Page: "Cholesterol: Synthesis, Metabolism, and Regulation."
National Health Service: "Dietary Advice to Lower Blood Cholesterol Levels."
Wiener Medizinische Wochenschrift: "Cholesterol metabolism-physiological regulation and pathophysiological deregulation by the endoplasmic reticulum."
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