All about cholesterol

Written by Luisa Müller
15 minutes reading time
17. July 2023 zuletzt aktualisiert am 1. August 2023 von

Have you ever wondered what cholesterol is all about? Or whether your body really needs cholesterol? And if so, for what? Is there good and bad cholesterol? Can you influence the cholesterol level yourself? Then we have something for you! With the following article, we would like to help you shed some light on the meaning of the ominous “oh-so-evil” cholesterol. Let’s go!

Table of contents

    1. what actually is cholesterol?

    Cholesterol can be produced by our body itself, but it can also be absorbed with food via animal foods. The body’s own production is responsible for around 90% of the cholesterol content and thus greatly dwarfs the proportion of cholesterol ingested with food. It is a natural substance, but it is found only in animal and human metabolism. From a chemical point of view, it is classified as a so-called “steroid”. Plants do not have cholesterol, but they do have so-called phytosterols, which are very similar to cholesterol. So far, so good. Another important question is whether our body needs cholesterol at all.

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    2. does my body need cholesterol?

    The answer is clear: Yes, absolutely! We need cholesterol for many functions of our body, without which we would be quite stuck.

    Cholesterol is a building block of our cell membrane

    Cholesterol, for example, is a very important component of our cell membrane. Together with a few other substances (the phospholipids and certain proteins), it forms a protective shell for all our cells. The cholesterol is responsible for ensuring that this shell is nice and stable. Simply put, our cells would simply be too soft without cholesterol. Thus, the cells would not be well protected and information could not enter our cells. As a component of the cell membrane, cholesterol is found in all organs. However, our brain is the one that contains the most cholesterol (about 20% of the total cholesterol in the body). Here, the largest part is found in the so-called “myelin sheaths”. These insulate our nerve fibers and ensure smooth signal transmission. Disorders of cholesterol metabolism are therefore also associated with diseases of the central nervous system (e.g. Alzheimer’s or Parkinson’s disease).

    Cholesterol is the starting material for many important hormones

    But cholesterol has even more up its sleeve! Not only is it a vital component in the brain, but other organs require cholesterol as well. It is the substance from which certain hormones are formed in our body – steroid hormones. These include:

    • Sex hormones (testosterone, estrogen, progesterone). Estrogen and progesterone play a very important role in the regulation of the female cycle and pregnancy. Testosterone is responsible, among other things, for sperm formation and growth in men, but also has an influence on the psyche in both sexes.
    • Mineral corticoids (aldosterone). Aldosterone, which is formed in the adrenal gland, is a crucial regulator of our electrolyte balance and thus also has an influence on blood pressure.
    • Glucocorticoids (cortisol). Cortisol, which is also produced in the adrenal gland, is involved in glucose regulation and our immune system, among other things.

    Bile acids are formed from cholesterol

    Are you thinking to yourself, “But pretty important this cholesterol.”? There is actually more to come! In order for us to produce bile acids in our liver cells, we need – surprise – cholesterol! It serves as the starting material for the two most important bile acids, cholic acid and chenodesoxycholic acid. They are essential so that we can properly digest ingested fats. By the way, cholesterol can also be removed from the body through the excretion of bile acids. This is important because all substances formed from cholesterol, as well as cholesterol itself, are rapidly consumed in the body. However, due to their chemical structure, they cannot be completely broken down and must therefore be excreted with the bile.

    Vitamin D3 is formed with the help of the sun and a cholesterol precursor

    So. Let’s add one more: Last but not least, our body makes vitamin D3 from cholesterol. With the help of sunlight, vitamin D3 is synthesized from a direct precursor of cholesterol (7-dehydrocholesterol). We need this vitamin to regulate our calcium concentration. It affects intestines, kidneys and bones. Whew! So far, it sounds like cholesterol is something pretty cool, right?

    Der Stoffwechsel von Cholesterin. Angepasst aus Löffler, Petrides, Heinrich: Biochemie & Pathobiochemie; 8. Auflage, Springer Verlag

    3. is there good and bad cholesterol?

    So cholesterol is important for many things. But why does everyone always talk about good and bad cholesterol? What’s behind it? To answer this question, we need to clarify how cholesterol is distributed in our body. Whether supplied or self-produced, it is sent on its way by the liver. To enable the “fatty” cholesterol to travel through our “watery” bloodstream to the various organs, the body has come up with something clever: The so-called VLDL molecules (VLDL stands for very low density lipoprotein) help with transport. This VLDL can grab cholesterol and deliver it to the various organs. On board it also packs, for example, fatty acids and a few vitamins. The more substances the VLDL delivers, the smaller it becomes and at some point it is an LDL molecule(low density lipoprotein). If there is excess cholesterol in our body, a kind of cab comes again to bring it back to the liver: the HDL molecule (HDL stands for high density lipoprotein). This reverse transport is called reverse cholesterol transport.

    You can remember the following:

    • HDL and LDL are transport proteins. They transport cholesterol, but also other substances, through our body.
    • LDL transports cholesterol from the liver to other organs.
    • HDL returns excess cholesterol to the liver.

    Very often, LDL is referred to as the “bad cholesterol,” while HDL is referred to as the “good cholesterol.” Since HDL ensures that unneeded cholesterol is collected again, it is usually seen as the good cop – LDL, on the other hand, as a kind of “cholesterol dealer”, is seen as the bad cop. But is it really that simple?

    VLDL, LDL, HDL - who's the bad guy?

    When it comes to this question, a simple answer is difficult. However, we try to summarize the current state of knowledge to the best of our knowledge in an understandable way for you. VLDL, LDL and HDL are – as we already know – transport proteins. You can’t easily divide them into “good” and “bad.” We rely on all forms. However, there are correlations between the respective amounts in our bodies and our state of health. High levels of LDL in the blood have been identified in many studies as a risk factor for cardiovascular disease. However, the development of these diseases is a very complex process. The starting point is usually arteriosclerosis. Here, inflammation can occur in our blood vessels due to various risk factors (e.g. smoking, stress, obesity). Over the long term, the resulting inflammation leads to a kind of junk pile (plaques) in the bloodstream. This increases the risk of our blood vessels becoming too narrow in these areas or closing completely.

    And what does that have to do with LDL now?

    If our blood vessels are somewhat damaged (due to risk factors already mentioned), certain substances can accumulate more easily in the walls. These include (among others!) LDL particles. These are then oxidized and, via a few more steps, lead together with other substances to the plaques in our bloodstream. A very crucial point here is that while LDL particles are present in these deposits, they are not the sole cause of these plaques. For example, muscle cells, fatty acids or immune cells can also be found here. In addition, it is probably less important how much LDL, but how much oxidized LDL (oxLDL) we have. By the way, we also encounter oxidation in everyday life: olive oil that has gone rancid or rust on your beloved bicycle are also consequences of oxidation. But when do we have a lot of this oxidized LDL? Unfortunately, we have to go into a bit more detail about this.

    Does it depend on the size?

    In the case of LDL, it seems to be, because not all LDL is the same. There are large, fluffy LDL particles and small, compact LDL particles. The smaller and more compact they are, the easier they can penetrate the walls of our bloodstream. Once there, they are oxidized and the scenario just described can begin. However, these small particles not only penetrate more easily, they are also very susceptible to being oxidized. Pretty uncool. In line with this, the risk of cardiovascular disease has been shown to increase the more of these small particles (called “small density”, or sdLDL particles) we have in our blood. We’ll summarize briefly: Our LDL should be as big and fluffy as possible, because the denser versions seem to do more damage to our artery walls – and thus our health.

    And what exactly does HDL do now?

    HDL contains substances that can prevent oxidation. Thus, it is not only responsible for “picking up” excess cholesterol, it also ensures that our bloodstream is protected from harmful reactions. Fittingly, low HDL levels are considered a risk factor for cardiovascular disease, while high levels are considered protective. The question of how one can influence one’s own LDL and HDL values and which values are considered normal is addressed later in this article.

    Let’s hold the following:

    • Our body needs VLDL, LDL and HDL to transport various substances.
    • There are different sizes of LDL, and we should have as little small density LDL and oxidized LDL as possible.
    • HDL appears to protect us from oxidized LDL. Low HDL levels are considered a risk factor for cardiovascular disease. High values represent protection against these diseases.

    Cholesterol and triglycerides

    When you talk about cholesterol levels and cardiovascular disease, you can hardly get past triglycerides. They can be taken in with food or produced by the body from carbohydrates when there is a calorie surplus and are a kind of energy store. They are transported from the liver to various cells mainly by VLDL. Triglycerides in the blood are an independent marker (i.e., a biological characteristic) for assessing the risk of cardiovascular disease. However, they are also associated with changes in cholesterol levels. Thus, when elevated, they are associated with low HDL, high LDL, and elevated small density and oxidized LDL levels.

    Foto: Shutterstock / Good Mood

    4. Can I influence my cholesterol level myself?

    The answer is “yes.” Our cholesterol levels are influenced by many factors: our age, gender, genes, infections, stress, how much we exercise… By eating healthy and making sure you get enough exercise, you can get the most out of your blood levels. How different food components affect your cholesterol levels is summarized for you in the following section.

    How do different food ingredients affect my cholesterol levels?

    Dietary cholesterol

    “Don’t eat too many eggs, it’s quite bad for your cholesterol.” You’ve probably heard this phrase before, right? But is that actually true? Nope, not really. The effects of dietary cholesterol are generally not very pronounced. However, it should be mentioned that there are large individual variations here. Our body can adapt to some extent by regulating its own production and absorption. However, these regulatory mechanisms are highly dependent on other factors – the type and amount of food consumed at one time, how much cholesterol is already present in the blood, genetic aspects, …. Unfortunately, it is therefore not possible to say how strongly cholesterol levels are affected by eating a cholesterol-rich diet that suits every person. The only thing that is certain is that in healthy people the effects are much less than previously thought.


    Maybe you’ve stumbled across margarine or yogurt drinks in the supermarket that were fortified with phytosterols? The reason is this: phytosterols (the plant counterpart to cholesterol) lower cholesterol absorption, resulting in lower total and LDL cholesterol levels in the blood. However, current studies are inconclusive as to the extent to which this influences the risk of cardiovascular disease. There are concerns that foods that have been additionally fortified with phytosterols may actually increase the risk. Long-term studies are needed to draw a clear conclusion in this regard.

    Trans fatty acids

    With trans fatty acids, on the other hand, one statement is very clear: stay away from them! The fatty acids found primarily in industrially processed foods greatly increase LDL and triglyceride levels while lowering our HDL. That’s a combination we absolutely want to avoid.

    Saturated fatty acids

    Most saturated fats can raise LDL cholesterol. However, as previously mentioned, the influence is strongly dependent on whether the person is intrinsically healthy, as well as on genetic factors. And for those who only skimmed the last section: Whether LDL is a risk factor or not depends in particular on the health of the vessel walls and inflammatory processes in the body. Although the ketogenic diet contains higher amounts of fat than other diets, it also has an anti-inflammatory effect. Additionally, we can mention that medium-chain saturated fatty acids (MCTs) can have a beneficial effect on our cholesterol levels. Studies show that the intake of lauric acid – contained in large quantities in coconut oil – positively affects our cholesterol levels. It is supposed to increase HDL cholesterol and thus steer the ratio of LDL to HDL in a “healthier” direction.

    Monounsaturated fatty acids

    Monounsaturated fatty acids, which are found in olives or avocados, for example, have a positive effect on the LDL/HDL ratio. Super!

    Polyunsaturated fatty acids

    Polyunsaturated fatty acids have a somewhat inconsistent effect on HDL and LDL levels. However, omega-3 fatty acids in particular (from nuts or fatty fish, for example) have been shown to lower triglycerides and increase HDL. Hooray for omega-3 fatty acids!


    An extremely high-carbohydrate diet can raise our plasma triglycerides and lower HDL. This is especially common with extremely low fat diets. It is not advisable to eat a lot of sugar, fructose or simple carbohydrates in general, because our liver then forms a lot of fat molecules (this is controlled by insulin). We will explain how this works another time). This in turn increases our amount of LDL molecules in the blood. Low-carb high-fat diets, on the other hand, have a positive effect on the LDL/HDL ratio. In addition, ketogenic diets have been shown to cause a shift in favor of the large, fluffy LDL particles. Although low-fat diets can lower total cholesterol, they usually lower HDL in particular – but as we explained, that’s not what we want.

    We summarize:

    • Dietary cholesterol has less impact on our cholesterol levels than previously thought.
    • Phytosterols lower cholesterol levels but do not appear to improve cardiovascular disease risk.
    • Trans fatty acids have a very bad effect on blood cholesterol composition.
    • According to current studies, saturated, monounsaturated and polyunsaturated fatty acids are predominantly positive factors in relation to our cholesterol levels (provided they are not consumed in combination with fast carbohydrates, e.g. sugar and white bread).
    • Low carb high fat diets also show beneficial effects when it comes to our cholesterol levels.

    Practical tip: Which values should I have checked?

    What values should I have tested by my doctor to determine my own cholesterol status?

    You want to have your cholesterol level determined? As standard, total, HDL and LDL cholesterol are determined by the physician. The individual components are influenced differently and also have different effects on our health. The total cholesterol value (consisting of VLDL, LDL and HDL) itself therefore has little informative value. Especially from the ratios of total and LDL cholesterol to HDL cholesterol, better estimates of the risk of cardiovascular disease can be made. It is generally possible to have sdLDL and oxLDL measured as well, but this is currently not (yet) part of the standard program.

    The following points can generally be used as a guideline:

    • Total cholesterol levels should not go to extremes. So be neither very low, nor very high.
    • Low HDL is not good. Very often, the ratio of LDL to HDL is used to estimate our blood levels. The current body of research suggests that the ratio of total cholesterol to HDL is also critical to our health status. Both ratios should be as low as possible – our HDL value thus as high as possible.
    • Smalldensity and oxidized LDL should be low.

    These standard cholesterol markers should also be usefully supplemented by other blood lipid values to better assess the risk of cardiovascular disease. This includes, above all, the determination of triglycerides in the blood. There are also a few other candidates, which we will discuss in more detail in another article. The following overview summarizes target guideline values for the individual cholesterol markers as well as triglycerides in the blood. Please keep in mind that these are values that could vary to a small degree between different laboratories and physicians.

    • Total cholesterol< 200 mg/dl
    • HDL> 50 mg/dl
    • Total cholesterol:HDL< 3.5
    • LDL:HDL< 3.5
    • Triglycerides< 150 mg/dl

    Nice2know: Is there actually a difference between cholesterol and cholesterol? No. Both terms denote the same thing. Whereas in German one can use both terms, in English, for example, one uses only “cholesterol”.

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    This article was written by

    Luisa Müller

    Luisa ist die Autorin dieses Artikels. Sie hat an der TU München ihren Bachelor in Ernährungswissenschaft und ihren Master in Nutrition and Biomedicine erfolgreich abgeschlossen. Nachdem sie einige Jahre in der Diabetes- und Adipositasforschung gearbeitet hat, wurde sie Teil des Foodpunk-Teams, wo sie bis September 2020 die Science-Redaktion geleitet hat.

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