Cholesterol has gotten a bad rap over the years, but it’s essential for human life. It is not only a necessary component of cell membranes, but also an important starting material for the production of sex hormones in the adrenal grands, ovaries and testicles. In addition, vitamin D, which is so important for our metabolism, is formed from cholesterol under the skin. Most cholesterol is needed for the production of bile acid in the liver. Due to the many functions of cholesterol in the body, it is also able to produce cholesterol itself. This means that 90% of the daily amount of cholesterol needed is produced by the liver. In contrast, only 10% of total cholesterol is absorbed with food.
Cholesterol is a fat-like substance and, like triglycerides and long-chain fatty acids, is insoluble in water, meaning it cannot circulate freely in the blood (blood consists of 70% water). Therefore, the fats are transferred to a water-soluble form, the so-called lipoproteins.
The exogenous metabolic pathway
Dietary fats absorbed through the intestine - cholesterol, triglycerides and long-chain fatty acids - are packed in lipoprotein shells in the intestinal wall and thus enter the vascular system via the lymph channels. From there they are distributed throughout the body. With the help of enzymes, triglycerides and individual fatty acids are broken down, which are needed for energy production and various metabolic processes. The remaining residual particles are absorbed by the liver.
The endogenous metabolic pathway
The liver produces various lipoproteins from the residual particles, among other things LDL cholesterol. The LDL is absorbed into the cells via special LDL receptors found on almost all cell types and thus removed from the bloodstream. Unfortunately, the absorption of LDL cholesterol into cells is not unlimited. If the supply of cholesterol from the blood exceeds the needs of the cells, the LDL receptors on the cell surface are reduced and the cells absorb less and less LDL cholesterol from the blood. As a result, a large part of the LDL cholesterol present in the blood oxidizes and is absorbed by the immune system’s scavenger cells (macrophages). So-called “foam cells” are formed, which contain large amounts of cholesterol. Over time, these cells die off and release cholesterol crystals, which promote the deposition of plaques in damaged vessels – arteriosclerosis develops.
HDL cholesterol is formed in the intestine and liver as well as in the blood while metabolizing other lipoproteins. These can – and this distinguishes them from other lipoproteins present in the blood – absorb oxidized LDL cholesterol and transport it back to the liver, where it is then used to produce bile acids.
Primary and secondary lipometabolic disorders
Approximately 30 percent of diagnosed hypercholesterolaemia are primary or familial hypercholesterolaemia. Primary or familial hypercholesterol anaemia is attributed to a gene defect. This gene defect causes fewer LDL receptors to be formed on the cells and thus reduces the absorption of cholesterol into the cells - with the result that the LDL concentration in the blood rises rapidly.
Often, however, an elevated cholesterol level is secondary. The reason for this may be, for example, a nutrition that is too rich in fats, which in particular contains too many saturated fatty acids and trans fatty acids. But a nutrition high in carbohydrates and low in fiber also contributes to this. Diseases such as hypothyroidism, diabetes or renal dysfunction can also cause elevated cholesterol levels. Furthermore, medication such as cortisone, antihypertensives or beta-blockers are suspected of having a negative effect on cholesterol levels.
What role does nutrition play?
Dietary and lifestyle changes are core elements of prevention and treatment of dyslipidemia. In general, a nutrition that is simply low in cholesterol is not recommended. The cholesterol in food usually has only a small effect on blood levels. We only absorb 500-600mg of cholesterol per day from our food. That's about 2 eggs, any additional cholesterol will not be absorbed. You could eat 20 eggs and still would only absorb about 600mg. It is much more important to have a balanced diet in which, high-quality omega-3 oils, sea fish, lots of fresh vegetables, herbs, fruits, as well as high-fiber foods are on the menu.
Influence of carbohydrates on cholesterol levels
A low-carbohydrate diet (low in processed and sugary carbs) has a positive effect on blood lipid levels and cholesterol. This was observed by scientists in a study of nearly 180 overweight middle-aged men. In the subjects who only met their energy requirements with only a quarter of carbohydrates instead of a half, the harmful triglyceride levels and unhealthy LDL cholesterol in the blood already showed a decrease after three weeks. This effect was also observed if the participants did not lose weight.
The explanation for this is provided by the metabolic intermediate product acetyl-CoA. It is produced during the breakdown of carbohydrates, fats and proteins, is needed for energy production and at the same time is also the starting substance for the body’s own cholesterol synthesis. With a high consumption of carbohydrates, especially those with a high glycemic load, more acetyl-CoA molecules are formed, which then stimulate cholesterol formation when no energy is needed, for example in the form of exercise and activity.
Vegetables - cholesterol-lowering
Fiber-rich foods, which are mainly rich in soluble fiber, such as apples, legumes and oats, have a positive influence on LDL levels. Their direct effectiveness is mainly based on their ability to bind bile acids in the intestine and excrete them. The more bile acids are bound and disposed of in the intestine by the soluble fiber, the less cholesterol is reabsorbed into the bloodstream. As a result, the liver removes more cholesterol from the bloodstream for the production of bile acid – the level of LDL cholesterol in the blood drops.
In addition to soluble fiber, plant foods also offer a special group of bioactive substances, the so-called plant sterols (phytosterols). These are particularly useful in reducing the absorption of cholesterol from the intestines into the bloodstream.
Plant sterols compete on the micelles in the small intestine with the absorption of cholesterol, so that cholesterol in the presence of plant sterols is increasingly excreted in the stool. This also means that less cholesterol is absorbed into the body, whether it is food cholesterol or the cholesterol that enters the intestines with bile acid. Plant sterols are found naturally in vegetable oils, pumpkin seeds, sunflower seeds or pine nuts and other nuts.
In addition to abundant fiber and phytosterols, vegetable foods also provide a high proportion of other secondary plant substances (carotenoids, polyphenols, sulfides, etc. ), which may protect LDL cholesterol from oxidation. The free radicals that accumulate in the body during the metabolic process or also due to stress are absorbed by the antioxidants and thus prevent them from joining with the cholesterol-containing fat particles.
Avoid hidden and damaging fats
The quality of dietary fats also has a major influence on the concentration of lipoproteins. Neither cholesterol nor fats are "dangerous" substances, but essential to life. The problem is usually that too many fats with an unfavorable fatty acid composition are consumed. A scientific study shows that on average 70 % of the daily amount of fat is absorbed as hidden fat (e. g. in sausage, cheese, chocolate, sweet pastries, snacks etc. ). However, it is now known that the fatty acid pattern in nutrition influences the composition, size and oxidation tendency of LDL cholesterol.
Therefore, the focus should be on monounsaturated and polyunsaturated fatty acids. A wide variety of studies have shown that replacing saturated fatty acids and trans fatty acids with omega-3 fatty acids (sea fish, cold-pressed vegetable oils, walnuts, seedlings) helps to activate the LDL receptors on the cells to absorb more LDL cholesterol.
Conclusion:
With balanced nutrition rich in vital substances, as well as by avoiding industrially processed foods and a healthy lifestyle, which means integrating exercise into everyday life and reducing stress, a secondary lipometabolic disorder can be kept in check. At the same time, other risk factors for cardiovascular diseases such as high blood pressure or blood sugar as well as obesity can be reduced.
In the Metabolic Balance program, analysis of blood values can determine whether the problem is primary or secondary hypercholesterolemia. Not only values such as total cholesterol, HDL or LDL cholesterol are decisive, but also glucose and triglyceride values must be taken into account in order to be able to make the appropriate nutrition recommendations. Simply avoiding foods high in fat and cholesterol can only reduce elevated cholesterol levels to a limited extent.
Sources:
Scholz R: Medizinische Biochemie, Band 9/10 „Cholesterin, Lipoproteine und Steroidhormone“, Zuckschwerdt-Verlag
Deutsche Gesellschaft für Ernährung e.V. Evidenzbasierte Leitlinie: Fettkonsum und Prävention ausgewählter ernährungsbedingter Krankheiten. Version 2015;
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