Cholesterol, HDL and LDL in Relation to Fats

--> There has been a great deal of misconception about Cholesterol, HDL, LDL and fats.  To understand their difference it is good examining their definition and their individual roll.

 Cholesterol

Cholesterol is an organic chemical substance technically classified as a waxy steroid. It is a crystalline substance and should not be confused with HDL (high-density lipoprotein), LDL (low-density lipoprotein) or fats. Cholesterol is by itself not fat, but is soluble in fats. That is why it’s sometimes classified as lipid.

The liver, intestine, adrenal glands and reproductive organs, primarily produce approximately 80% of the total body cholesterol in the blood by means of a 37 step process.

Cholesterol is essential for the building of membranes, proper membrane permeability, the skin’s ability to produce vitamin D, the production of nerve fibers, sex hormones, bile acid, digestive hormones and other hormones and their derivatives, and thus is necessary for proper functioning of the entire body.

Bile contains bile salts which solubilize fats in the digestive tract. Bile aid is necessary for the absorption of fat molecules as well as fat-soluble vitamins, A, D, E and K. Bile is synthesized in the liver from cholesterol.

Cholesterol is a very important precursor for the synthesis of vitamin D and bone density.

Cholesterol is very important for the synthesis of steroid hormones such as adrenal gland hormones, cortisol and aldosterone. These hormones affect the metabolism of carbohydrate, protein, minerals and fats. They also regulate the retention of salt and water. They control the maturation of white blood cells and activity of nervous system and the regulation of blood pressure.

Cholesterol is also important for the production of sex hormones such as progesterone, estrogens, and testosterone and their derivatives just to name a few of its functions.

High-density Lipoprotein (HDL)

Low-density Lipoprotein (LDL)

Lipo means lipid or fat. Protein is of a large number of organic compounds made up of amino acids arranged in a linear chain. Lipoprotein is actually a complex particle that shapes like a disk. It has an exterior composed of amphiphilic proteins and lipids with outward facing surfaces being water-soluble and inward-facing surfaces lipid-soluble.

Triglycerides and cholesterol esters are carried internally, while phospholiphids and non-esterfied cholesterol are transported in the surface of the lipoprotein. Lipoprotein transports the fat-soluble cholesterol to body tissues for utilization. Other lipoproteins transports excess cholesterol not utilized by these tissues to be excreted or recycled. Even though some cholesterol is conveyed as fatty esterified cholesterol while others are carried as alcohol, they are all identical.

There are several categories of lipoproteins. Five of them are the high-density lipoprotein, low-density lipoprotein, very high-density lipoprotein, intermediate-density lipoprotein and chylomicrons. The chylomicrons are the least dense while the LDL being the densest. Less dense lipoproteins have more lipids and less protein. Different lipoprotein contains apolipoproteins that serve as ligands for specific receptors on cell membranes. This serves to determine the starting and ending of the cholesterol being transported.

Chylomicron is involved in the transportation of fats from the intestine to muscles and other tissues that need fatty acids for energy or fat production.

Intermediate-density lipoprotein molecules supply the blood vessels with cholesterol-loaded triacylglycerol. IDL that are not taken up by LDL receptors continue to lose triacylglycerol into the blood stream until they themselves form LDL. LDL has the highest percentage of cholesterol within them and so are the major carriers of cholesterol.

Excess triacylglycerol and cholesterol not utilized by the liver for the production of bile acids are carried by the very-low-density lipoprotein (VLDL). Apolipoprotein of low-density lipoprotein binds with receptors then goes through a process resulting in cholesterol esters which are used for membrane biosynthesis or become esterified and stored within a protective cell.When there is adequate cholesterol in the cells, LDL receptors synthesis is blocked so that new cholesterol from LDL cannot be taken up. Conversely, a deficiency of cholesterol prompts the synthesis of more LDL receptors.

A malfunction of this system results in many low-density lipoprotein molecules without receptors accumulating in the blood. These lipoproteins oxidize. Macrophages engorge themselves with these oxidized low-density lipoprotein and form foam cells. When these foam cells are trapped in the walls of the blood vessels they contribute to atherosclerotic plaque formation.

High-density lipoprotein collects cholesterol from cells by means of an enzyme that converts the free cholesterol into cholesteryl ester. These esters are isolated into the core of the newly synthesized high-density lipoprotein. As the HDL circulate through the blood stream, it collects cholesterol and phospholipid molecules from cells and other lipoproteins . The cholesterol collected is transported mainly to the liver to be excreted into the bile, which convert it into bile acid then sends it to the intestine. HDL also transports cholesterol to other organs such as the adrenals, ovary and testes for the synthesis of hormones. A small portion of the cholesterol secreted into the digestive tract is re-absorbed into the blood. Several steps in the metabolism of High-density lipoprotein contribute to the transport of cholesterol from foam cells to the liver.

In human, cholesteryl ester transfer protein, exchanges triglycerides of very-low-density lipoprotein (VLDL) with cholesteryl esters of High-density lipoprotein (HDL) resulting in VLDL becoming LDL that are removed from circulation by LDL receptor pathway. The unstable triglycerides become degraded leaving a small HDL particle to restart the uptake of cholesterol from cells.

It would appear as if protection against cholesterol deposits depends largely on, among other things, the production of HDL. Fats inclusive of saturated fats are among the materials necessary for the manufacture of cholesterol. Therefore, diets deficient in essential amino acids, essential fatty acid, nutrients such as vitamins A, C, K and calcium necessary for their absorption and utilization or any other nutrients necessary for the production of protein, will result in decline of protein production and repairs inclusive of lipoproteins, apolipoprotein and associated enzymes. A decline in lipoprotein especially HDL or other associated proteins or enzymes could mean abnormal cholesterol level in the blood.

With such well organized system as this there should be no problem. However in cases of poor nutrition resulting in insufficient HDL circulating to collect excess cholesterol, allowing unused foam cells to form and become lodged in the blood vessels, tissue rigidity and eventually blockages results.

So is it true that we’re to abstain from foods supplying cholesterol? Research has indicated that foods supplying cholesterol, especially when consumed in conjunction with high fiber foods, do not affect cholesterol level. Fibers usually absorb and eliminate most if not all dietary cholesterol. In addition most dietary cholesterol is esterified. Esterified cholesterol is poorly absorbed. Furthermore, some plants produce phytosterols, which are substances chemically similar to cholesterol. Phytosterols compete with cholesterol for absorption in the intestinal tract, thus potentially reduces cholesterol re-absorption. Because phytosterols are foreign to animal cells, when absorbed in the intestinal lining in place of cholesterol, they usually excrete into the gastrointestinal tract for expulsion. It follows then, that your body primarily produces the cholesterol in the blood and any additional absorption is minimal and is usually compensated for by reduction in cholesterol synthesis.

When we eliminate fats including saturated fats from our diet we’re in effect eliminating essential fatty acids, fat soluble vitamins, fat soluble phytonutrients and other nutrients that are fat soluble. Besides, saturated fats are necessary for cholesterol production. Cholesterol is essential for body functions and bone density. So what should we do to regulate cholesterol level?

 How to Prevent Cholesterol Problems?

There are four basic food groups for proper body function.  These are fats, carbohydrates, water, and proteins.  It thus follows that all categories of fats, as well as all categories of carbohydrates and proteins are necessary for proper body function.  Saturated fats are fundamental for the production of  cholesterol, which in turn is vital for various body functions,  inclusive of  brain function, reproductive function, digestive function, and with the aid of the suns radiation, the productions of vitamin D by skin cells which in turn is necessary for the production of bone density, and so on. Carbohydrates covers all forms of starches, fruits and vegetables, while proteins include meats, fish, eggs, dairy products, nuts, seeds, grains  and so on.

Eight to ten (8 - 10) glasses of pure water should be consumed each day. 

It follows that, the common practice of abstinence might just be the means to other problems while still graveling will controlling your cholesterol.  So what is the correct rout to preventing cholesterol problems?

Everything is created in proper balance. 

Hence finding the right balance in your diet is vital for the promotion of good health.  Another fact to observe is that all that is natural and edible is critical for the maintenance of good health.  Your meals however, should be eaten in proper balance to prevent simultaneous excesses and inadequacies of various foods or food groups.  It should be born in mind that the aim is to keep the range of your body’s pH at its proper level of approximately 7.35 to 7.45 (slightly alkaline).  This can be achieved from balanced diet.

In a balanced diet each food group is consumed in specific proportions that are proven healthful. The book "Nutrition That Keep You Alive" explains in details what a balance diet is. With the suggested spread of the different food groups the consumption of fats are minimal. Therefore there is no need to place specific emphasis on the reduction of or the elimination of fats from the diet.

More emphasis should be placed on eating all your foods in the proper proportion. A balance diet includes foods rich in phytonutrients and the necessary anti-oxidants to slow oxidation. Also adequate levels of high-fiber foods with their phytosterols which helps to regulate cholesterol absorption will be included. 

To regulate cholesterol, nuts and seeds are important in the diet. To regulate cholesterol it is also important to consume both animals as well as plant source of protein and the other foods required for the utilization of protein.