No life without Cholesterol!

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Cholesterol has been one of the most maligned and misunderstood substances of the twentieth century. Eating foods high in cholesterol was long thought to raise blood cholesterol levels, something considered to be so dangerous that some of the most nutritious foods on the planet -- like liver and egg yolks -- were demonized as enemies of our arteries.

Unfortunately the campaign against cholesterol has washed away from our daily menus many of the most important foods we should treasure for excellent health and vitality

The Facts

Cholesterol is a major constituent of each vegetal or animal cell !

Cholesterol is found in every cell of your body. It is especially abundant in the membranes of these cells, where it helps maintain the integrity of these membranes, and plays a role in facilitating cell signaling-- meaning the ability of your cells to communicate with each other so you function as a human, rather than a pile of cells. Molecule for molecule, cholesterol can make up nearly half of the cell membrane. Since it is smaller and weighs less than other molecules in the cell membrane, it makes up a lesser proportion of the cell membrane's mass, usually roughly 20 percent.

Cholesterol is also present in membranes of organelles inside the cells, although it usually makes up a smaller proportion of the membrane.

Cholesterol is an amphipathic molecule, meaning, like phospholipids, it contains a hydrophilic and a hydrophobic portion. Cholesterol's hydroxyl (OH) group aligns with the phosphate heads of the phospholipids. The remaining portion of it tucks into the fatty acid portion of the membrane.

By stabilizing certain proteins together in lipid rafts, cholesterol is important to helping these proteins maintain their function.

This could range from forming blood clots or thinning blood, to allowing sugar into your cells, to burning fat, to regulating calcium in your blood, and literally includes, in some way, most of the functions in your body. (¹)

Cholesterol Is Necessary for Digestion

The human body uses cholesterol to synthesize bile acids, which are important for the digestion of fats. The primary bile acid, cholic acid, is very similar in structure to cholesterol.

in order for the human digestive system to digest fats, they must be emulsified into the digestive juices, because the enzymes that break them down are water-soluble.

Bile acid synthesis is up-regulated by cholesterol and down-regulated by cholic acid. This means that the higher the cholesterol to cholic acid ratio is, the faster bile acids will be produced. As bile acids are produced, and the concentration of cholesterol lowers and the concentration of cholic acid rises, bile acid synthesis slows down.(²)

Vitamin D is Synthesized From Cholesterol

One of cholesterol's many functions in the body is to act as a precursor to vitamin D. Since cholesterol is a precursor to vitamin D, inhibiting the synthesis of cholesterol will also inhibit the synthesis of vitamin D. Since sunlight is required to turn cholesterol into vitamin D, avoiding the sun will likewise undermine our ability to synthesize vitamin D. And since vitamin D-rich foods are also rich in cholesterol, low-cholesterol diets are inherently deficient in vitamin D.(3)

Vitamin D is best known for its role in calcium metabolism and bone health, but new roles are continually being discovered for it, including roles in mental health, blood sugar regulation, the immune system, and cancer prevention.

Vitamin D3

When atmospheric conditions are ideal and skies are clear, 30 minutes of whole-body exposure of pale skin to sunlight without clothing or sunscreen can result in the synthesis of between 10,000 and 20,000 IU of vitamin D. These quantities of vitamin D are large, and therefore capable of supplying the body's full needs (4)

Synthesis of Steroid Hormones From Cholesterol

Cholesterol is the precursor to a hormone called pregnenolone, which has important functions itself, but is also the precursor to all other steroid hormones.

Pregnenolone is converted to progesterone, a sex hormone, which in turn is converted into cortisol, which regulates inflammation and blood sugar, aldosterone, which regulates mineral balance and blood pressure, or testosterone, a type of sex hormone referred to as an androgen, which regulates libido, muscle mass, and plays other roles.  testosterone is further modified, undergoing conversion to estradiol, a different type of sex hormone called an estrogen. (5)

 

The Myth:

Eating Cholesterol-Rich Foods Raises Blood Cholesterol Levels

The myth goes something like this: arteries are like pipes; cholesterol is gooey, sticky gunk. When you eat cholesterol, it winds up in your blood. If the cholesterol level in your blood gets too high, it starts caking up the pipes. Thus, if you don't want your pipes clogged, don't eat foods rich in cholesterol.

Such is the basic logic behind advice to avoid eating nutrient-dense foods

The truth :

Eating Cholesterol Does Not Raise Blood Cholesterol Levels

The truth is, however, that there is no direct connection between the amount of cholesterol you eat and the concentration of cholesterol in your blood. In most people, eating cholesterol has little or no effect on this amount. In about 30 percent of the population, eating cholesterol does in fact increase the concentration of cholesterol in the blood — but it increases the "good" cholesterol.

To put it in more scientific terms, eating cholesterol "results in a less atherogenic lipoprotein profile."

LDL Particle Size

Moreover, the actual number of LDL particles do not change at all; they just get bigger. When your doctor measures your blood cholesterol level, the lab reports it by weight. In America, this is usually in milligrams per deciliter. When your "cholesterol level" is high, this means that in a given measure of blood volume (such as a deciliter or a tenth of a liter) the total number of cholesterol-carrying lipoprotein particles weigh more. This could mean that you have more particles, or it could mean that the particles weigh more because they are carrying more cholesterol.

According to research, it is the small, dense LDL particles that raise the risk of atherosclerosis, while the large, buoyant LDL particles are safe. This may be because small, dense LDL particles are much more vulnerable to oxidation. People whose LDL is primarily small and dense have three times the risk of heart disease as people whose LDL is primarily large and buoyant.

In the egg-feeding studies, egg consumption makes the LDL particles of the "hyperresponders" get bigger, not more numerous. When they get bigger, they become less subject to oxidation and accumulation in atherosclerotic plaque

In over two thirds of the population, then, egg consumption leads to little or no change in cholesterol at all. In less than a third of the population, total cholesterol goes up, but both the ratio of LDL to HDL and the total number of LDL particles remains the same; the LDL particles just get bigger and safer.

If arteries were like pipes and cholesterol was like gunk, more gunk would just clog up the pipe — but arteries are nothing like pipes and cholesterol is nothing like gunk. Consider the myth busted.

References

(1)    Alberts, et al., Molecular Biology of the Cell: Fourth Edition, New York: Garland Science, 2002,.

(2)  (5) Harvey et al., Biochemistry: 3rd Edition, Baltimore: Lippincott Wiliams and Wilkins, 2005

(3)    Cannel, John, "Vit D: When Why Where and How Much," Wise Traditions 2005 November 12, 2005 (lecture).

(4)    Adams and Hollis, "Vitamin D: Synthesis, Metabolism, and Clinical Measurement." In: Coe and Favus, eds., Disorders of Bone and Mineral Metabolism, Philadelphia: Lippincott Williams and Wilkins (2002) p. 159.

(5)     

(6)    (7) Fernandez ML. Dietary cholesterol provided by eggs and plasma lipoproteins in healthy populations. Curr Opin Clin Nutr Metab Care. 2006;9:8-12.