What Is The Normal Role Of Cholesterol In The Body? - 2021

Why do we talk about 'good' and 'bad cholesterol?

Cholesterol is a subject of debate.

Experts argue among themselves, with contradictory controversies, about its real danger and whether or not it is necessary to take medication for high levels.

To put an end to the confusion, let's zoom in on this multifaceted molecule.

What is the typical role of cholesterol in the body?

Why do we talk about 'good' and 'bad cholesterol?

What are the risks of high cholesterol?

How can I reduce my high cholesterol?

Cholesterol is a subject of debate.

Experts argue among themselves, with contradictory controversies, about its real danger and whether or not it is necessary to take medication for high levels.

To put an end to the confusion, let's zoom in on this multifaceted molecule.

Cholesterol is a constituent of the membranes that surround cells. It is essential for the manufacture of hormones produced by the genital and adrenal glands.

The regulation of cholesterol depends on genetic and lifestyle factors. When the "bad cholesterol" level is too high, it becomes harmful to health.

The doctor then suggests a diet and medication lower the level.

Summary:

1. What is cholesterol?
2. Mechanisms of cholesterol
3. The "bad" cholesterol
4. The "good" cholesterol
5. Causes and risk factors for hypercholesterolemia
6. Symptoms of hypercholesterolemia
7. Cholesterol measurement
8. The course of hypercholesterolemia
9. Cholesterol: the diagnosis to eliminate
10. Cholesterol treatment

[1] What is cholesterol?

Cholesterol is essential to life and is a constituent of the membranes that surround cells. It is also necessary for the manufacture of hormones produced by the genital and adrenal glands.

However, too much cholesterol (and other fats) in the blood leads to the formation of plaques on the artery wall: this is called atherosclerosis.

In the human body, cholesterol has two origins:

• 70-75% come from the liver ;
• 25-30% of the food.

• The international unit of measurement for total cholesterol is the millimole per liter or mmol/L. Normal levels of total cholesterol (TC) are
• Before 30 years: 1.50 to 2.0 g/L (4 to 5.2 mmol/L) ;
• After 30 years: 2 to 2.5 g/L (5.2 to 6.4 mmol/L)

[2] Mechanisms of cholesterol:

In the blood, circulating lipids (fats), including cholesterol, are not soluble in water. They are, therefore, "transported" by soluble proteins. These carrier proteins are called lipoproteins.

By convention, there are three types of lipoproteins:

• Low-Density Lipoproteins or LDL, light density;
• Very Low-Density Lipoproteins or VLDL, very low density;
• High-Density Lipoproteins or HDL, high density.

[3] The "bad" cholesterol:

LDL (bad) cholesterol takes cholesterol from the liver and carries it around the body. This cholesterol tends to settle in the arteries and clog them. This is the "bad" cholesterol.

[4] The "good" cholesterol:

HDL collects the cholesterol deposited in the vessels and returns it to the liver. This is the "good" cholesterol. After a blood test, it is determined which part of the cholesterol is carried by HDL and which part is carried by LDL.

The average level of HDL-cholesterol (the "good" cholesterol) is as follows:

• Male: 0.4 to 0.65 g/L or 1.0 to 1.65 mmol/L ;
• Female: 0.5 to 0.8 g/L or 1.3 to 2.0 mmol/L.

This level varies according to diet, lifestyle, and the use of certain medications.

In the case of a diet rich in animal fats and therefore in cholesterol, LDL increases. The overall blood cholesterol level increases.

The heavy transporters (HDL) are overwhelmed and can no longer do the job. The fats are deposited on the atherosclerotic plaques.

Below 0.35 g/l or 0.9 mmol/l (measured several times), there is a cardiovascular risk. If the ratio of total cholesterol to HDL > 5: the relative coronary risk is multiplied by 20.

The ratio of total cholesterol to HDL-cholesterol must be :

• Less than 5 in humans ;
• Less than 4.4 in women.

The danger comes from excess LDL cholesterol. The other fraction, HDL-cholesterol, on the contrary, has a protective role since it favors the reduction of atheromatous plaques.

[5] Cholesterolemia:  Causes and risk factors: 

Food

Cholesterol is mainly made in the liver from fats in the diet. Cholesterol is not related to the number of fats ingested but to their quality.

The fats in the diet are made up of fatty acids that are of three kinds:

(1) Saturated fatty acids:

In food, the "bad" cholesterol is found only in products of animal origin rich in saturated fatty acids. 

There are none in fruits, vegetables, vegetable oils. Fish contain very little.

The primary sources of cholesterol are eggs, whole milk, offal (liver and heart), cold cuts, and meat, especially red meat (beef and others). Cholesterol is invisible in beef.

In beef, 95% of cholesterol is in red meat, very little in fat;

(2) Monounsaturated fatty acids:

They are neutral. It is, for example, peanut oil, olive oil...;

(3) Polyunsaturated fatty acids:

They are protective and are found in certain vegetable fats (corn oils, soybeans, sunflower, rapeseed, nuts) and fish oils. They are not involved in the synthesis of cholesterol. They increase the level of beneficial HDL for the elimination of cholesterol.

An unsuitable diet (high in animal fats) can lead to hypercholesterolemia and, therefore, atherosclerosis.

However, nature is unfair, and there is an individual (often family) sensitivity to animal fats. Some individuals will be able to eat high amounts of it and maintain low cholesterol levels.

Others will have high cholesterol with a low-fat diet of the same type.

After 80 years, the relationship between cholesterol and mortality is somewhat reversed: low cholesterol levels increase the risk of cancer, depression, non-cardiovascular death.

(a) Iatrogenic or drug-induced hypercholesterolemia:

Several medications can increase cholesterol levels:

• Oral contraceptive ;
• Specific Hormone Replacement Treatments for Menopause (THS);
• Some beta-blockers ;
• Some thiazide diuretics ;
• Retinoids used in the treatment of acne ;
• Corticosteroids.

(b) Birth control pill and hyperlipidemia:

In the absence of associated risk factors (including tobacco) and a diet low in saturated fats, the pill can be prescribed up to a total cholesterol level equal to 3 g / l. A very low-dose tablet is, however, recommended.

The pill remains contraindicated in case of hypertriglyceridemia > 2 g / l.

(c) Hypertriglyceridemia:

Triglycerides (TG) are mainly carried by VLDL and depend principally on the metabolism of sugars; they are deleterious because they provide atheroma.

The standard level of triglycerides is:

• In Male: 0.5 to 1.5 g/L or 0.6 to 1.7 mmol/L ;
• In Female: 0.4 to 1.6 g/ L or 0.45 to 1.5 mmol/ L.

Isolated hypertriglyceridemia (HTG) is not an independent coronary risk factor. An HTG must always evoke or search for:

• Obesity ;
• Alcohol consumption is sometimes even moderate;
• A carbohydrate metabolism disorder: diabetes and insulin disorder;
• Kidney failure ;
• Hypothyroidism ;
• A drug origin (oral contraceptive, vitamin A derivatives, thiazide diuretics, beta-blockers, corticosteroid therapy);
• More rarely: stress, viral hepatitis, AIDS, pancreatitis...

(d) Protective factors:

Several biological factors are "protective" factors:

• HDL-cholesterol > 1.6 mmol / l or 0.60 g / l (confirmed on several measures), allows to subtract a risk factor;
• Women before menopause - or postmenopausal women on TSH (hormone replacement therapy).

[6] Symptoms of hypercholesterolemia:

Strictly speaking, there are no clinical signs that would allow hypercholesterolemia to be evoked with certainty.

The search for this metabolic disorder must be carried out :

• Either during a systematic health check-up;
• Or in a patient who already has a cardiovascular risk factor (arterial hypertension, obesity, smoking, men over 45, menopausal women, oral contraceptives, family history of cardiovascular disease, stress, etc.);
• Or in a subject already suffering from a condition linked to atherosclerosis (arteritis of the lower limbs, angina pectoris, myocardial infarction, stroke, renal insufficiency, etc.).

[7] Cholesterol measurement:

The simple determination of total cholesterol (TC) is not sufficient. HDL cholesterol and triglycerides (TG) must also be determined.

From these three figures, it is possible to calculate the "bad cholesterol" or LDL cholesterol level:

• In grams/litter: LDL-cholesterol = Total cholesterol - HDL-cholesterol - (TG x 0.16) ;
• In moles/Liter: LDL-cholesterol = Total cholesterol - HDL-cholesterol - (TG x 0.37).

[8] The course of hypercholesterolemia:

The major complication of high cholesterol is the development of atherosclerosis. The symptoms presented by the patient will depend on the arteries affected:

• Coronary arteries: angina pectoris (angina) and myocardial infarction;
• Cerebral arteries: strokes due to thrombosis of one or more arteries supplying the brain;
• Aorta: aortic aneurysm, aortic dissection;
• Lower limbs: obliterative arteritis of the lower limbs (AOMI);
• Renal arteries: renal hypertension due to nephroangiosclerosis (obstruction of renal arteries and arterioles).

[9] Cholesterol: the diagnosis to eliminate:

The isolated finding of total hypercholesterolemia is not sufficient to affirm the chronic existence of this metabolic disorder. Some hypercholesterolemia is secondary:

• The use of medication: cortisone, the pill, retinoids, antihypertensives, etc.;
• To the presence of disease: hypothyroidism.

In this case, it is sufficient to stop taking the medication responsible or to treat the hypothyroidism for the lipid metabolism disorder to disappear.

Other hypercholesterolemias are genetic and hereditary and particularly difficult to treat.

It is also essential to know that a meal rich in fat can occasionally increase cholesterol levels. A return to a regular diet is then sufficient to normalize the blood cholesterol.

[10] Cholesterol treatment:

What are the options for reducing the amount of cholesterol in the body? The most straightforward and most sensible solution is to reduce cholesterol intake through diet. This is the first thing a doctor will suggest if your blood lipids are low. If this is not enough, the doctor may use medication.