Dr. Sean Wheatley, PhD – Researcher and Trainer in Public Health/9 January 2017
We’re often told that we need to worry about our cholesterol levels, and that high cholesterol increases our chance of having a heart attack, stroke or other horrible things. But we’ve also all heard of “good” cholesterol and “bad” cholesterol. It can all get a little confusing, so what’s really going on?
What is cholesterol?
Cholesterol is a waxy, fat-like substance that our body needs for:
* Brain function,
* Helping to make the outer coating of cells,
* Making the bile acids that we need to help digest food in the gut,
* Allowing the body, with the help of sunlight, to produce vitamin D (a lack of vitamin D can lead to Rickets),
* Supporting the production of hormones (including oestrogen in women and testosterone in men).
Overall cholesterol is very important for a number of different reasons. Without it our bodies simply wouldn’t be able to function!
So why has cholesterol got such a bad reputation?
Cholesterol has had the blame for cardiovascular disease placed firmly at its door. National guidelines worldwide and dozens of treatments have often been focused on reducing it, and you only have to sit and watch the television to see how many products will claim to help you lower yours.
Cholesterol can be deposited in the walls of blood vessels, causing the build-up of fatty streaks which increase our risk of cardiovascular disease. This increase in risk is because these fatty streaks can make the gap though the blood vessels smaller so it becomes harder for the blood to get through, or bits can break off and cause blockages.
But, as you’ll see, this doesn’t mean that the cholesterol itself is the problem!
What are “good” and “bad” cholesterol then?
Despite what we’re told, there is only one type of cholesterol. Cholesterol is cholesterol is cholesterol! Cholesterol cannot travel through our body to where it is needed on its own though as it cannot mix with our blood, so it is transported by carriers called lipoproteins. It is these different types of lipoprotein that are referred to as “good” or “bad” cholesterol, but in reality they are not cholesterol at all- they just carry it.
High-density lipoproteins, or HDLs, are what are referred to as the “good” cholesterol. Now although they aren’t really cholesterol at all, as stated above, the description as “good” is fair. HDLs take any excess cholesterol in the blood to the liver where it can be removed or repackaged. This stops any excess being deposited in the blood vessel walls, so having more HDL is good for our health.
On the other hand we have low-density lipoproteins, or LDLs, which are generally referred to as “bad” cholesterol. Now this is where things get slightly less clear-cut. LDL isn’t all bad, it carries cholesterol and fat around our body to places where it can be used – and potentially has a role in other bodily functions. It is differences in the size and, particularly, the number of the LDL particles that makes the difference.
Our LDL should be large. Large LDL particles are good at carrying things around. They are sturdy and can comfortably carry the load, which means they are less likely to “drop” it or get stuck in the blood vessel walls. This makes it less likely that we will get a build-up of cholesterol and fats in our blood vessels. If we have large LDL that can carry lots of cholesterol, it also means we don’t need that many of them- and it is ultimately the number of LDL particles we have that is the best indicator of risk.
Small LDL particles however can cause problems. They are not as stable, so are more likely to drop the load they are carrying. They are also not able to carry as much cholesterol. This means that if we have small LDL particles we need more of them to carry the same load a few large LDL particles could manage. Having more LDL particles increases the risk of some of them getting damaged (“oxidised”). The smaller LDL particles also hang around in our blood for longer, which further increases the risk of them getting damaged. When the LDL particles are damaged they are more likely to drop their load or get stuck in our blood vessel walls – the processes that actually cause the problem, particularly if this happens consistently over an extended period of time. The cholesterol itself is just the innocent passenger, but gets the blame anyway!
We can think of these different types of LDL as being similar to traffic on a motorway. If we only have a few trucks on the road then they are able to easily carry large loads, and there isn’t much chance of a crash happening. This is similar to when we have large LDL particles, as they’re stable and we don’t need that many to transport the cholesterol etc. around. When there are lots of cars on the road however, that aren’t as effective at carrying the load, there is a much increased risk of their being collisions. This is similar to when we have small LDL particles, as we need more to carry the same amount the large LDL would be able to carry- and they aren’t as good at carrying it!
The more “crashes” there are, the more cholesterol and fat gets spilled and/or stuck in the blood vessels, the higher our risk. But it is the differences in the carriers that increase the risk of crashes, nothing to do with what is actually being carried.
So what health markers should I pay attention to?
Practically speaking, what this means is that there are some traditionally used markers that are not actually that useful for assessing our health:
* Total cholesterol is influenced by HDL, small LDL, large LDL and triglycerides (a type of fat, which is bad for our health if we have too much in our blood). This means that the number we’re given for total cholesterol includes some things that we want more of (HDL) and some things we want less of (small LDL and triglycerides)- so it is more useful to know how much of each of these things we have rather than knowing the combined total!
* Knowing our total LDL is not much use either, for similar reasons. Without knowing what size our LDL is or how many LDL particles there are we don’t really know if our risk levels are increased or not (LDL-c, the number we are usually given, tells us how much cholesterol is being carried by the LDL; but nothing about how it is being carried) . The use of LDL is also limited because rather than actually measuring it directly an equation is (almost always) used to estimate it. This equation (which is based on total cholesterol, TG and HDL) makes some assumptions that may not be true for everyone, so we can’t always trust the number we get anyway!
There are no longer cut-points recommended for these markers in clinical practice, which reflects the fact they have limited use. Markers that are of more use include:
* HDL is good, having more HDL is better (unless it is REALLY high, which might suggest something else is going on). HDL levels should be above 1mmol/L for men and above 1.2 mmol/L in women.
* Triglyceride to HDL ratio is a good indicator of what size our LDL particles are. As discussed above this is an important indicator of health, we want to have large ones rather than small ones. The size itself is not measured as standard in the UK though, so this ratio provides a good proxy measure. Ideally our triglyceride to HDL ratio would be less than 0.87, whilst if it is more than 2.62 that is an indicator of high risk.
There are a number of other markers that can give us a good indication of the state of our cardiovascular health- such as blood pressure, measures of insulin resistance, and markers of inflammation. There isn’t the space here to go into much detail on that now, but we may well revisit that at a later date. Overall though it is the clustering of risk factors that generally gives us the best idea of how healthy we are – if you have multiple markers that are outside of a “normal” range this is a more clear indicator that you are at an increased risk than if you just had a single sub-optimal result.
What can I do to reduce my risk?
Although it is increasingly common for people to be prescribed medication, usually a statin, when their GP is concerned about their “cholesterol” there are a number of lifestyle factors which have been shown to be effective at improving our health in this area. There is again not enough space here to discuss this in detail; but making some changes to your diet, increasing your physical activity, only consuming alcohol in moderation, and stopping (or at least reducing) smoking are all proven ways of achieving this.
The latter three are all fairly straightforward adaptations, but which dietary changes to make is less clear-cut. I’m not going to open that can of worms here, but some sound advice that most would agree upon includes reducing processed foods and avoiding refined carbohydrates and sugars! Why not take a look at the dietary approaches section of our website if you want to find out more, with the Mediterranean diet in particular being recognised as “heart-healthy”.
So what’s the bottom line?
Cholesterol is essential for life, and on its own is not bad for our health. When cholesterol becomes deposited in the walls of our blood vessels it can start to cause problems, but it is problems with the carriers that causes this to happen rather than because we have too much of cholesterol itself.
This means that rather than being worried about our cholesterol levels it is more useful to look at markers which give us some information about the state of the lipoprotein transporters (HDL, Large LDL, and small LDL) that carry it around! It is possible to make improvements in these things through lifestyle modifications alone.
As with all our blogs and other work we’d love to hear your thoughts and feedback, so feel free to comment below, drop me an e-mail at firstname.lastname@example.org or tweet us/me at @XPERTHealth or @SWheatley88.