In my previous two blogs I started a series of communications on macronutrients. We have already spoken about carbohydrates and started the conversation on lipids, fats in particular, so today we are going to finish our conversation on lipids by talking about one very important lipid - cholesterol.
What is cholesterol?
The word "cholesterol" comes from Greek radicals "chole-", which means "bile", "stereos"(solid) and the ending "-ol" designating the nature of the molecule being an alcohol (Figure 1). Cholesterol is found in almost all animal products such as eggs, bacon, meat etc. Perfect example of a cholesterol-rich meal would be an omelette with some bacon and sausages. Unfortunately, many people do not understand the role of cholesterol in our diet and metabolism and claim that this kind of breakfast is nothing but toxic. As you likely noticed, cholesterol is some sort of a boogey man in nutrition, and today I will try to show you that things are a little more complicated than it's usually portrayed by mass-media and cholesterol is not that bad in the end of the day.
What happens to cholesterol in our bodies?
When we consume fats and cholesterol they are absorbed in our intestines and form little globules of fat and cholesterol knowns as chylomicrons. These globules get to the liver, where they are deconstructed into fatty acids, glycerol and cholesterol and repackaged again into larger globules known as lipoproteins. Then, these lipoproteins are released into bloodstream and cholesterol and fat are transported to all organs of our body. I have already mentioned these lipoproteins when I was talking about fat. There are different kinds of them depending on their density, but for the moment we just have to know that they exist. I'll make a special blog on so called "bad" and "good" cholesterol, I promise, but today I will only say that indeed high cholesterol levels are associated with heart disease, but at the same time there is evidence that contradicts this theory, and quite strongly - for example, there are studies showing that dietary cholesterol is not related to high serum cholesterol levels. Also, there is way more to the mechanism of cholesterol involvement into formation of atherosclerotic plaques, enough to say that cholesterol is more of a bystander than a culprit here.
What are the functions of cholesterol?
Cholesterol has quite a few important functions in our bodies: it is critical for our digestion - while in the liver, cholesterol is used to create bile, which main function is to help emulsify the dietary fat in the gut. Without bile we wouldn't be able to properly process fatty foods and, accordingly, we would be deprived from a valuable source of energy and structural elements for our bodies.
Speaking of structural elements - cholesterol is a part of our cellular membranes. Approximately 30% of our cell membranes are made of cholesterol (Figure 3). It helps maintaining the fluidity and integrity of our cellular membranes, which simply cannot be overemphasized. It is a critical vital function - without cholesterol our membranes would not be able to function properly and would break down very easily.
Another function of cholesterol is also vital and almost always overlooked - it is a structural base of vitamin D and... drum roll... all steroid hormones! Yes, all steroids are made of cholesterol. Steroids are so important that I will definitely make a special blog, likely several, on them. But for now, I just want to emphasize that you cannot maintain your body, have good sexual function, regulate multiple metabolic processes in your body without cholesterol, let alone build a healthy and athletic body.
In fact, cholesterol is so important that our body can actually produce de novo - it takes a lot of energy, but our body makes it happen just because cholesterol is that important! There are medications, statins, that lower the cholesterol levels in our body by blocking its production. These medications are used very widely and, unfortunately, they have quite a few side effects, but I would like to draw your attention to a specific one - rhabdomyolysis, a condition when muscle fibers start breaking down. In my opinion it is a good indicator that cholesterol is important for our muscles.
I hope that now, with all this information, you do not feel that cholesterol is something bad for your health. It is, in fact, an important essential nutrient, a molecule that serves multiple roles in our bodies and we definitely need it for our survival and development. I will proceed with making two blogs about other macronutrients - alcohol and protein - and then I will definitely return to this topic as I really want to clear up some misconceptions about cholesterol and lipids in general.