<div class="pull-left">https://steemitimages.com/DQmT16NTSq1R5H2pivQxAetwZgpSSYtSH4ZgFbMK2Z8PyRu/image.png</div>

Before we even get started it is important to remember that in biology and medicine the reality is often far more complicated than current scientific understanding (and tenfold times more so for a primer article like this one).

Let's start off with a  technical point, when people talk about cholesterol they are often referring to the proteins that carry cholesterol around the body and not the cholesterol itself.

#### Lipoproteins

HDL (high density lipoprotein) which is the smallest and most dense lipid carrier will transport fat from around your body to the liver. LDL (low density lipoprotein) and VLDL (very low density lipoprotein) which is the biggest and least dense carrier takes fat around your body to the cells and depending on the type, can also increase the risk of fatty buildup in the blood vessels.

<div class="pull-right">https://steemitimages.com/DQmZoKKaQoCK3QqmjdxBv2XxyMXZNxsjfmoQyjVAr6WbiX1/image.png</div>

So good and bad cholesterol are not actually cholesterol it is actually LDL and HDL where LDL if often termed 'bad' and HDL is often termed 'good'.

Even that break down is misleading because the large and fluffy LDL is actually good for you ([reference 1](https://www.ncbi.nlm.nih.gov/pubmed/21360474), [reference 2](http://clinchem.aaccjnls.org/content/51/7/1192)).

There is also the small particle size LDL and it is this type that is associated with inflammation and blockage of the arterial pathways. Most medical bloodwork does not make this distinction so your doctor will just assume that a high LDL count means small particle LDL and is therefore 'bad'.  Something to keep in mind.

In summary: The big transporters (LDL, VLDL) are the transporters that move towards your body cells, where the cholesterol is used. The smaller, denser transporters (HDL) move towards the liver which is the organ that can convert then so they can be removed from the body.

<center>![](https://steemitimages.com/DQmWgnnYGwNvLG2TdGh7Ah78j9zTAAQn7kQ4GrETVgvzFp5/image.png)</center>

#### Cholesterol

Let's get away from all that discussion about HDL and LDL and on to cholesterol itself.

The cholesterol  molecule has a number of important uses in the body:

* it is a precursor (or building block) for all of your steroid hormones as well as bile acid and vitamin D,
* it is used in the make-up of cell wall structures and in
* the sheath for nerve cells.

As mentioned cholesterol molecule is a precursor building block for hormones like cortisol, aldosterone and the sex hormones: testosterone, progesterone and estrogen.

It is also the precursor molecule for vitamin D and the liver will convert it into bile acids for use in digestion of fats and is the ultimate excretion path for cholesterol out of the body.

Cholesterol also makes up a part of your cell wall membranes. It helps to keep your cell walls flexible when cells get cold and help them maintain sufficient rigidity when get too warm. So cholesterol acts somewhat like an all-over plastifier, in addition to being a basic building block for vitamin and hormones.

Finally, cholesterol is also a material found in the makeup of myelin which is the insulating sheath around your nerve fibres. This is the reason why it is said that brains are very rich in cholesterol.

Generally you need cholesterol to function and live. If you got rid of cholesterol you would die.

#### Health Concerns and Common Health Advice

LDL has been implicated in promoting atherosclerosis but as I said at the start of the post it is always more complicated than that. The big fluffy LDL is apparently not bad for you but the smaller LDL particles are bad for you.

Essentially the latest recommendations are to keep the HDL and LDL ratios at an optimal level (higher HDL levels and lower LDL levels are often said to be good).

<div class="pull-left">https://steemitimages.com/DQmNqVQCTtw5aoA6G9vZSNRnPnt3md1unEgY3EShvFUQ7qq/image.png</div>

The wrong type of LDL can cause your blood vessels to inflame which means they will get narrower. This means that the heart will need to pump harder to get oxygen around your body and that will in turn raise blood pressure which causes even more complications.

Less blood flow also means less oxygen to your tissues which is a big problem in, and of, itself.

The general advice for improving your HDL and LDL levels are aerobic exercise and diets high in omega-3 fatty acids (salmon, fish oil). Red wine is also touted as a benefit but I am not so sure whether alcohol can be a net benefit. Cutting carbohydrates out of your diet has also been [found to improve](https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/cholesterol/) the HDL-LDL profile significantly.

So it seems that the best food to eat are those that keep people lean and non-diabetic and this means eat more natural foods whether they be fatty or not and avoid the sugary junk.

<div class="pull-left">https://steemitimages.com/DQmW5fmRx5KhCbrVZFfgxWtY5Uy1MV1bwEoFS1bZ2XzZnV4/image.png</div>

Having said all that one need to manage one's expectations with respect to diet and aerobic exercise. These are very important in determining your levels but medical science is learning that [genetics seems to carry more weight](http://www.geneticlifehacks.com/cholesterol-and-your-genes-part-1/).

Some genetic variations will predispose people to higher levels than other people and for these people getting their levels down without drugs is very hard task indeed. 

Even so it never hurts to engage in aerobic exercise and to have a healthy diet.

#### Closing Words
The more we learn about health and diet the more it seems that the food our ancestors ate is actually the best thing for us.

It's weird that we had to go through all that science and expensive time-consuming research over the years just to find out this simple and basic truth.

#### Post Sources

This [thread](https://www.reddit.com/r/explainlikeimfive/comments/8aqpof/eli5_whats_cholesterol_and_why_is_it_good_or_bad/) on Reddit inspired this post and provided a lot of the clarifications in this article.

https://en.wikipedia.org/wiki/Cholesterol
https://courses.washington.edu/conj/bess/cholesterol/liver.html
https://www.ncbi.nlm.nih.gov/m/pubmed/22607825/
https://www.ncbi.nlm.nih.gov/pubmed/21360474
http://clinchem.aaccjnls.org/content/51/7/1192
https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/cholesterol/
http://www.geneticlifehacks.com/cholesterol-and-your-genes-part-1/