#1/n: Introduction - What is cholesterol?

After putting this off for a while, I have begun consolidating and publishing my research on lipoproteins and cholesterol. After recovering from my health issues by switching from a vegan, low-fat diet to a high-fat meat based diet, I had to find out more about cholesterol. Why was fat demonized so much? What was the deal with cholesterol? And my cholesterol has jumped up by 100 points, I feel better than ever did with a low cholesterol of 150 mg/dL on a vegan diet to about 250 mg/dL. I have talked about my health issues elsewhere, but a markable difference with my change in cholesterol has been my immunity. I don’t get sick anymore. I used to be sick with the flu pretty much every month, but now I feel tired for a few days, and get better. It never becomes a full fledged cold, sore throat and blocked nose. My quality of life has improved significantly. Acne, Constipation, IBS, Period cramps, Depression, all resolved.

I mean, I was pretty much at the brink of suicide due to my health issues, after following a 'perfectly' healthy vegetarian/vegan diet. I stuffed myself with lentils, whole grains and vegetables each meal, but never felt truly ful or satiatedl! I avoided ghee like it would kill me immediately with a heart attack. I was terrified of red meat - I was convinced that a steak today guaranteed a diagnosis of colon cancer tomorrow. I will discuss topics such as satiety, malnourishment, eating disorders and their role in diabetes & obesity in my other articles, but the main chunk of my research has been - WHAT CAUSES HEART ATTACKS?

This is a series of articles that I will be writing on cholesterol, lipoproteins (including Lp(a)) and some of the lipid-regulating drugs.

So, what is cholesterol? - The chemistry.

First off, cholesterol is not a fat. These are 2 different things.

Cholesterol is a very important molecule present in all living organisms of animal origin. It has very important biological functions that I will discuss below. If you are a plant, your cells will be made of 'phyto'sterol.

Cholesterol is an alcohol, which is why it ends with 'ol'

Fat is usually made up of fatty 'acids'

Now, an acid an alcohol can combine to become an 'ester'. So cholesterol can either exist in 'free' form or in 'ester' form. In order for cholesterol to become an ester (and vice-versa), an enzyme called ACAT is necessary for the conversion.

Why does cholesterol exist and where does it come from?

Most of my patients actually have no idea what cholesterol is, but you will be surprised to know that cholesterol is ESSENTIAL for all animal life to exist. Here are some functions of cholesterol.

• Every cell membrane in the body is made of cholesterol. Without properly functioning cell membranes, your body will not work properly. Hormones, enzymes and proteins will not be able to communicate with each other. I am not joking, but when I discuss cholesterol with my doctor friends, they forget this basic fact ..
• Cholesterol is an antioxidant. So cell membranes are made of cholesterol and fatty acids. Some fatty acids easily get damaged due to various reasons. Especially if the fatty acids are of PUFA variety. So, if a cell membrane is damaged due to smoking, stress etc, cholesterol is necessary to FIX that damaged cell membrane. Plus, cholesterol is precursor to an antioxidant called CoQ10 which is essential for each cell in our body to produce ATP!
• The brain is made of cholesterol, and fatty acids. (2 different things, but they often go together). Nerve cells are coated with myelin - a fatty sheath which is necessary for nerve function, memory, cognition etc.
• Vitamin D is made from cholesterol.
• Hormones (steroid hormones) are made from cholesterol. This includes stress hormones cortisol, blood pressure regulating hormone aldosterone, and reproductive hormones estrogen, progesterone, testosterone.
• Bile acids are made from cholesterol and are essential for absorbing fat-soluble vitamins, and also for aiding in digestion and assimilation.
• Cancer and immunity. Cholesterol plays an important role in the immune system, and this ties in with it's anti-oxidant function as well.

30 to 40 gm of cholesterol exists in the human body. Most of this exists within cell membranes itself.

25% comes from the diet, while 75% is produced in the body. Every cell in the body produces cholesterol.

The liver produces about 20% of the cholesterol that the body needs. The rest of it is produced by the cells themselves. Every cell in the body is capable of producing cholesterol.

SO cholesterol cannot be bad. If cholesterol is bad, then life on Earth is a 'bad'. Capitalism, however? Certainly bad - Especially when money gets in the way of Good Science! 👀

Most of the cholesterol we eat in our diet - does not get absorbed. The cholesterol we eat has almost nothing to do with blood cholesterol levels. [1]

Yes, you heard that right.

It is impossible for our body to absorb cholesterol from the diet from the gut. This is because most of the cholesterol in animal food is found as 'esters' [see figure above], and only “free” cholesterol can be absorbed in the gut. Instead, the cholesterol absorbed in our gut is actually recycled cholesterol that is produced in the body itself.

Yes, the body recycles cholesterol to use it because THAT is how much you need cholesterol. It is precious.

That is, most of the cholesterol that our body uses, and absorbs from the gut is made by our body itself. 

AND NO, THE BODY DOES NOT PRODUCE CHOLESTEROL IN ORDER TO CAUSE HEART ATTACKS. If that were the case, every animal in the world should be getting heart attacks. Even they have cells, and livers that produce cholesterol!

Why eating animal fat increases cholesterol while plant-fats decrease cholesterol?

So humans are animals, and plants are plants - so our cells are slightly different. We need CHOLE-sterol NOT phyto-sterol. But, phytosterol and cholesterol are very similar in structure, so they can compete with one another for absorption. If you eat a lot of phytosterol rich plant oils, they can compete with cholesterol for absorption. And remember you are NOT a plant, so if your body cells are made of phytosterol instead of cholesterol, it will make your cell membrane far less flexible, INCREASING risk of heart attacks and strokes. [2]

COMING UP = 

What is blood cholesterol? What is LDL & HDL? Why is one called good and the other called bad?

[1] Peter Attia explains the detailed mechanisms of cholesterol absorption in the gut in part I of his series on cholesterol: The straight dope on cholesterol – Part I - Peter Attia

[2] Nadir Ali - Dangers of Plant Sterols