Cholesterol
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What is cholesterol?
Cholesterol is a waxy, organic compound belonging to the steroid family that is present in blood plasma and all animal tissues. Its molecular formula is (C_{27}H_{46}O).
Cholesterol is essential for life and is a primary component of cell membranes. It serves as the starting material for the synthesis of bile acids, steroid hormones, and vitamin D. The liver and other organs synthesize cholesterol, which is transported through the bloodstream by lipoproteins.
High cholesterol levels can cause atherosclerosis, increasing the risk of heart attacks and strokes. Lowering the dietary intake of cholesterol, especially animal fats, is the chief means of avoiding high cholesterol levels in the blood.
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Why do our bodies need cholesterol?
Cholesterol is essential for life. It is a primary component of the membrane that surrounds each cell. The normal human body contains about 100 grams of cholesterol, although this amount can vary considerably among healthy people.
Cholesterol is the starting material for the synthesis of bile acids, steroid hormones, and vitamin D. Because cholesterol is insoluble in water, it is carried through the circulatory system by transport particles in the blood called lipoproteins. The rigid structure of cholesterol strengthens the cell membrane.
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Where does cholesterol come from in our bodies?
Cholesterol, a waxy substance in blood plasma and animal tissues, is essential for life. It is a primary component of cell membranes and a building block for bile acids, steroid hormones, and vitamin D.
Cholesterol comes from two main sources:
* Production in the body The liver and other organs synthesize cholesterol. The liver regulates cholesterol production based on dietary intake.
* Dietary intake Humans consume cholesterol through a normal diet, mainly from animal fats.The body maintains cholesterol balance through absorption, synthesis, and elimination as bile acids. High blood cholesterol is a risk factor for heart disease.
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What is the difference between 'good' (HDL) and 'bad' (LDL) cholesterol?
Cholesterol is transported through the bloodstream by lipoproteins. The two main types are low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs).
LDLs carry cholesterol from the liver to cells, but can contribute to plaque buildup in arteries, increasing the risk of heart disease and stroke. Because of this, LDL cholesterol is often called "bad" cholesterol.
HDLs, on the other hand, may transport cholesterol away from the tissues and back to the liver, where it is broken down and excreted. HDLs may also reduce atherosclerotic buildup, which is why HDL cholesterol is often called "good" cholesterol.
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How can high cholesterol affect our health?
High levels of cholesterol in the bloodstream can cause atherosclerosis, where cholesterol and other fatty substances accumulate in blood vessel walls. These deposits narrow blood vessels, restricting blood flow and potentially leading to heart attacks and strokes.
Cholesterol is transported through the bloodstream by lipoproteins. Low-density lipoproteins (LDLs) carry cholesterol from the liver to cells, contributing to atherosclerotic deposits, while high-density lipoproteins (HDLs) may remove excess cholesterol from tissues, reducing the risk of plaque buildup.
To maintain healthy cholesterol levels, it's important to lower your dietary intake of cholesterol by reducing total fat intake and replacing saturated fats with unsaturated fats.
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What are some ways to keep cholesterol at healthy levels?
To maintain healthy cholesterol levels, reduce your intake of saturated fats found in animal products and replace them with unsaturated fats from fish and vegetable oils. Decreasing overall fat consumption and limiting cholesterol-rich foods like egg yolks and organ meats can also help. Regular exercise and smoking cessation are also beneficial.
If lifestyle changes aren't enough, hypolipidemic drugs such as statins, bile acid sequestrants, and niacin can help lower cholesterol levels, though they may have side effects.
Maintaining a desirable blood lipid profile includes a total cholesterol level below 200 mg/dL, HDL above 40 mg/dL, triglycerides under 150 mg/dL, and LDL levels varying based on heart attack risk.
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Cholesterol, a waxy substance that is present in blood plasma and in all animal tissues. Chemically, cholesterol is an organic compound belonging to the steroid family; its molecular formula is C27H46O. In its pure state it is a white, crystalline substance that is odourless and tasteless. Cholesterol is essential to life; it is a primary component of the membrane that surrounds each cell, and it is the starting material or an intermediate compound from which the body synthesizes bile acids, steroid hormones, and vitamin D. Cholesterol circulates in the bloodstream and is synthesized by the liver and several other organs. Human beings also ingest considerable amounts of cholesterol in the course of a normal diet. A compensatory system regulates the amount of cholesterol synthesized by the liver, with the increased dietary intake of cholesterol resulting in the liver’s decreased synthesis of the compound.
High levels of cholesterol in the bloodstream are an extremely important cause of atherosclerosis. In this disorder, deposits of cholesterol and other fatty substances circulating in the blood accumulate in the interior walls of the blood vessels. These fatty deposits build up, thicken, and become calcified, eventually converting the vessel walls to scar tissue. The deposits narrow the channels of the blood vessels and thus can constrict the blood flow, causing heart attacks and strokes. High levels of cholesterol in the blood (more than 240 mg of cholesterol per 100 cc of blood plasma) accelerate the buildup of cholesterol deposits in the vessel walls; people with high cholesterol levels thus eventually become more susceptible to coronary heart disease.
Cholesterol is insoluble in the blood; it must be attached to certain protein complexes called lipoproteins in order to be transported through the bloodstream. Low-density lipoproteins (LDLs) transport cholesterol from its site of synthesis in the liver to the various tissues and body cells, where it is separated from the lipoprotein and is used by the cell. High-density lipoproteins (HDLs) may possibly transport excess or unused cholesterol from the tissues back to the liver, where it is broken down to bile acids and is then excreted. Cholesterol attached to LDLs is primarily that which builds up in atherosclerotic deposits in the blood vessels. HDLs, on the other hand, may actually serve to retard or reduce atherosclerotic buildup.
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The chief means of avoiding high cholesterol levels in the blood is to lower one’s dietary intake of cholesterol. Because cholesterol is present in animal fats (i.e., saturated or polysaturated fats) but not in fats obtained from plant sources (i.e., unsaturated or polyunsaturated fats), this can be done by: (1) reducing one’s total intake of fats, (2) partly or wholly replacing one’s consumption of saturated fats with that of unsaturated fats, and (3) reducing one’s consumption of foods containing cholesterol. Thus, foods high in saturated fats, such as lard, butter, cheese, whole milk, red meat, candy, and baked goods containing shortening, would be avoided, as would such cholesterol-containing foods as egg yolks, shrimp, and brains and other animal organs. Unsaturated fats such as fish oils and corn, peanut, safflower, and soybean oils would be substituted for animal fats. Recently, the fish oils found in salmon, tuna, mackerel, and certain other marine fishes were found to raise HDL levels and thus reduce or retard atherosclerotic processes. Extensive research has now verified the causal relation between a cholesterol-rich diet, high blood cholesterol levels, and coronary heart disease, but authorities disagree about the overall value of long-term cholesterol reduction for the “normal” individual. See also lipoprotein.