Cholesterol Part I – Know The Basics
This has been a worldwide hot debate for decades, but what’s the big deal? Improve your understanding of this important, and constantly evolving area so that you can take more charge of your own health.
Interesting fact: most cholesterol is actually created by the body itself
What is cholesterol?
Cholesterol is a type of waxy fat (a.k.a. lipid) created in all animal cells that is vital for life to exist. All cells are capable of creating cholesterol within themselves for their own function and survival.
Cholesterol is also a required for the creation of vitamin D, stress hormones and sex hormones within the body. Furthermore, it plays a role in the absorption of the fat-soluble vitamins A, D, E and K.
Where does it come from?
Most cholesterol (85%) is actually created by your body itself (mainly in the liver), with only a small amount (15%) coming from our diet.
The cholesterol we consume is a slightly different molecule to the version in our body, making it more difficult for us to absorb from our intestines. The cholesterol we absorb is then compensated for by our body cleverly reducing cholesterol production (and vice versa); meaning that changing our dietary consumption of cholesterol is not necessarily the simple fix to lowering high serum (blood) levels.
Most people who have higher cholesterol naturally produce higher levels. Some are just better at absorbing it.
Does cholesterol harm us?
Well in short cholesterol itself is not harmful, it’s the type of transporter molecule (lipoprotein) that it is carried in that can be damaging to our blood vessels (cardiovascular system) – see below section.
3D Image of cholesterol causing atheroma build up in an artery
The 2 main ‘types’ of cholesterol
They are classified by the type of lipoprotein (transport particle created by the liver) that carries it around the body. The reason that cholesterol needs a lipoprotein is that cholesterol cannot travel through the blood on its own. There are 2 main commonly described types of cholesterol:
LDL (Low density lipoprotein) – ‘bad’ cholesterol
HDL (High density lipoprotein) – ‘good’ cholesterol
This type of cholesterol is known to increase the risk of cardiovascular disease (most commonly angina, heart attacks, strokes and peripheral vascular disease). This type of cholesterol is therefore harmful at higher levels in the blood and this is due to its involvement in the formation of atheroma (plaques) within blood vessels – causing narrowing (see below image).
Some LDL particles can pass into artery walls (endothelium) and are cleaned up by macrophages (type of white blood cell), through this process they form ‘foam cells’ that build up in artery walls and form atheroma. Once an atheroma has started forming it is easier for other LDL particles to get inside, again fuelling a vicious cycle…
A standard blood test estimates the concentration of LDL within the blood sample (it is actually not directly measured).
A smaller LDL particle is believed to be more dangerous as it can penetrate a small defect in the artery wall easier, sparking the process for atheroma formation.
To reduce atheroma formation, we must reduce LDL particle numbers.
LDL particle number/size is not routinely tested for in most standard laboratories around the world but has the potential to become the future basis for more precise cholesterol testing and management.
HDL is believed to reduce the risk of cardiovascular disease and this is because it is thought to remove LDL from atheroma. Research shows that people with higher HDL levels have lower risks of cardiovascular disease.
Triglycerides are another important type of lipid in the body primarily used for energy and measurable on a blood test.
If too much triglyceride is consumed (and not used up) they move out of blood and into adipose (fat) tissue for storage (causing weight gain and an increased risk of cardiovascular disease), and when required for energy they can move out of adipose tissue for use as muscle energy.
The rate at which you use up triglycerides depends very much on your metabolism / activity levels.
Gram for gram, triglycerides contain around twice as much energy as carbohydrates.
To reduce triglycerides weight loss and diet changes can really help – see the cholesterol part II blog for more information.
Plants do not create cholesterol and so we do not absorb cholesterol from plant foods. Instead we absorb phytosterols (plant-sterols) from some foods instead. These example foods have naturally occurring phytosterols:
Avocado, nuts, corn, fruits and seeds.
Phytosterols compete with cholesterol in the gut for absorption. Therefore, if you consume enough phytosterols then you can lower your body’s cholesterol.
There is a large market for dietary supplements built on this notion claiming to be able to lower LDL cholesterol. However, in some people high intake of phytosterols are believed to be potentially harmful and the effect of phytosterols on reducing the risk of CVD has still not been proven.
What lowers cholesterol?
- Low in saturated fats, low cholesterol foods (see part II blog) and low trans-fats
- A Mediterranean type diet to lower cardiovascular risk
Omega 3 Supplements
- Omega 3 may help to reduce triglyceride levels
- Omega 3 may help to increase HDL levels
- Supplements not routinely recommended in reducing risk of cardiovascular disease
- Statins (blocks the enzyme in the liver that creates cholesterol)
- Fibrates (reduce the level of triglycerides, may help HDL, no effect on LDL)
- Others (beyond the scope of this blog)
- Cholesterol is vital for life
- Dietary cholesterol intake makes little impact on our overall cholesterol levels
- LDL cholesterol is harmful
- HDL cholesterol is protective
- Natural phytosterols may help reduce cholesterol absorption
- Mediterranean diet with an active lifestyle is a good approach to lowering cholesterol
- Supplements of omega 3 are not routinely recommended
- Speak to your Doctor about arranging a cholesterol / lipid profile