Cholesterol & the lipoprotein cycle

So a quick (and simplified) biology lesson for todays post....

Hopefully your on-board with the fact that cholesterol isn't actually the killer substance that certain people/organisations/Dr's/etc would have you believe, but did you know how important it actually is?

Cholesterol is required to build cell walls, it is essential for building many of our hormones , it is a key part of our immune system, and essential for tissue repair. Cholesterol literally holds your body together and it is so important that the majority of our cells have the ability to manufacture their own cholesterol. Whilst talking about cholesterol it is important to also understand what triglycerides and lipoproteins are as well.

Triglycerides are a fat based fuel source made of three fat molecules grouped into one glycerol (or sugar-like) molecule. Triglycerides can be consumed through fat containing food and they can be created in your liver.

Cholesterol and triglycerides cannot travel around the bloodstream by themselves, and this is where lipoproteins come in. These act like 'boats' to carry cholesterol and triglycerides around the body. Lipoproteins are hollow spheres within which cholesterol and triglycerides are packed for delivery to the brain and body tissues. Lipoproteins move freely within the blood and there will be millions moving around your body at this very moment on delivery and collection duties. The lipoproteins all have a protein signalling molecule in their outer shell (called a apolipoprotein) to identify themselves to the various 'docks' in the body. There are two main types of lipoproteins in your body, LDL and HDL, HDL is unique and there are a number of classes of LDL.

VLDL (Very Low Density Lipoprotein) is where LDL starts and it is the largest lipoprotein. It is created in the liver and ferries cholesterol & triglycerides around the body. Its main function is to deliver triglycerides as a fuel to skeletal and heart muscle.

LDL (Low Density Lipoprotein) is formed when the VLDL drops off its cargo and shrinks in size, some cholesterol & triglyceride remains inside LDL and VLDL is used for both delivery and return trips in the cholesterol delivery system.

sdLDL (Small dense LDL) is created when LDL becomes distorted in an inflammatory environment. Your immune system will identify sdLDL as un-unwelcome guest and mop it up (but when the system is broken/overwhelmed this doesn't always work). Also unlike LDL, sdLDL is less likely to return to the liver, so will remain in the blood stream for longer which increases the chance of it becoming damaged further.

Now I've simplifying things somewhat but essentially VLDL transports triglycerides to muscles for energy, and then after delivering the energy it becomes LDL which continues to transport triglycerides and also distributes cholesterol to tissues. LDL then returns to the liver where remaining cholesterol is recycled and re-used and the cycle repeats.

HDL (High Density Lipoprotein) is a bit different and is created in the gut, it has many important functions and acts as the manager of the cholesterol/triglyceride transport system. It manages the cholesterol and triglyceride content of LDL by swapping cholesterol & triglyceride molecules with LDL as required, protecting LDL from oxidation damage. It also delivers cholesterol to the few tissues that LDL can't reach including the gonads and adrenal glands AND removes cholesterol from where it shouldn't be (like arterial walls).

So cholesterol is essential for our bodies to grow/function/repair and we have evolved a complex system to manage the distribution of this important substance so why the bad rap? Well like any system, when abused it can become damaged and dysfunctional, and this is where problems can occur. You've probably heard the terms 'good' and 'bad' cholesterol, HDL is this 'good' guy and LDL the 'bad' guy. Now this isn't a fair description as both LDL and HDL are essential in the cycle but low levels of measured HDL and high levels of measured LDL are symptomatic of underlying problems.  When LDL becomes damaged they no longer get recycled properly by the liver and instead hang around in the blood a lot longer than they are supposed too. If not cleaned up by the immune system they can end up inside inflamed arterial walls and this can lead to arterial plaque, blockages, and eventually heart attacks. HDL will try and clean this up but if the system is damaged then it can only do so much.  I'll try and cover how this system gets broken in more detail in a future post (spoiler alert its not from eating animals!) but its important to note that blocked arteries and heart disease are symptoms of a dysfunctional system and not a result of eating too much cholesterol, furthermore cutting dietary cholesterol will likely only cause other problems.

To track or not to track....

Fitness tracking is big business these days and the technology is advancing at a rapid pace. A glance around at peoples wrists will reveal that a large number of us have swapped the watch for a tracker, and if you listen to all the marketing you'd think that a fitness tracker was an essential tool to own in the pursuit of health and fitness goals.

I've owned a fitness tracker for the last three years  a Garmin Forerunner 225 to be precise which I purchased after careful consideration and plenty of shopping around. As well as being a waterproof GPS running watch, it had a built in heart rate monitor and doubled as a fitness tracker (steps, sleep, etc). It did everything I was interested in at the time, was a great tool, and as an engineer I do like having loads of data to analyse! However about 2 months ago, after 3 years of unfaltering service, it just died, turned itself off and refused to do anything ever again. Diagnosed as un-repairable by Garmin I was given the option of purchasing a reconditioned FR225. I didn't take Garmin up on this offer as technology has moved on a bit now and I was after an upgraded device so it looked like I would be splashing out on a new fitness tracker so off to do some market research.......

But I haven't yet, and after living without one for the last couple of months I'm in no particular hurry to get one. Its been interesting reflecting on why I first got a fitness tracker, the benefits of tracking and dare I say it the drawbacks.....

Whilst the sensing technology is impressive, some features of fitness trackers are arguably not essential, others definite gimmicks. For example I don't need a watch to buzz/flash/beep after I have been inactive for a certain period of time, I know when I've been sat on my arse for too long, I can feel my muscles stiffening up and the urge to get up and do something.

Whilst looking back at previous nights sleep patterns is interesting I know as soon as I wake up whether I have had a quality nights sleep or not, no need to check the log to find out exactly what time of the night a small child came and jumped on me! Unless you are completely out of tune with your body you'll know if you wake up feeling refreshed and ready to go, or if you'd rather just crawl back into bed and tell the world to poke it.

And as for counting steps, I never really paid much attention to this feature. I know when I have spent a full day on my feet walking and running, my muscles will tell me with that subtle ache of a day spent active. Likewise I'm well aware when I have spent a day stuck in-front of a computer.

I've observed some 'interesting' behaviors driven by fitness tracking. For example my nearest & dearest has often been seen walking on the spot in front of the telly of an evening to 'get her step count up', I've not conducted any deeper studies into this phenomenon but I would guess that she is not alone! Targets are a great way of changing behaviors but if we are not picky about our targets we may develop some unplanned behaviors. The theory behind a daily step target is to encourage people to move more throughout the day and engage more low level exercise (i.e walking), however 1/2 hour stepping on the spot in front of the telly to increase the total number of steps recorded during the day is not a substitute for actually spending the day striding around this beautiful planet.

My old Garmin pre-dated the 'smart watch' but a feature of most newer devices is the ability to link with your phone and display text messages, emails, call alerts, etc. I'm no Luddite (honest!) but I'm not at all convinced that there is a need to have these alerts instantly available on your wrist. It can be hard enough having a proper conversation without phone interruptions these days but at least most people will be able to put the phone away when required. A watch however is always there, and its becoming increasingly common to find people checking their watch mid conversation as alerts come through.

A fitness tracker can certainly be a useful tool, especially if you are trying to understand activity levels, identify sleep issues, etc. They can also help validate your intuitive senses, but, and there is a fairly sizeable but....in a similar way that over reliance on GPS navigation reduces our natural ability to navigate (I'm guilty as charged on this one!) over reliance on technology to tell us how active we have been, how well we have slept, etc may dumb down our natural intuition. Spending some time away from this data and instead properly focusing on how you actually feel during the day will tell you everything you need to know, whether you should rest more, move more, etc. 

While trackers are great for monitoring progress, and can keep you motivated to achieve your goals it’s easy to focus too hard on the numbers and beat yourself up if your pace is a little slower today than yesterday, or your walk a little shorter. With every activity tracked and recorded its easy to become fixated on constantly outdoing ourselves, and then the metrics can become a tool we use to judge ourselves, which I would argue is not healthy. Whilst it’s good to continue progressing in a positive direction an off day (or period of days) is quite normal and nothing to worry about, we all need to take it easy from time to time as pushing ourselves to the limit day after day will likely result in injury or burnout.

Whilst I have never used it, most trackers have a social media type sharing option that can connect you with friends and family who are likely to support and encourage you. Whilst this can provide a bit of helpful motivation, it can also turn into just another way that we compare ourselves to others. If you see that your friend’s weekly running mileage is significantly higher than yours, for example, it’s easy to feel inadequate. Not a healthy outcome when the reality is we should all be "running our own race".

In conclusion I think I'm going to treat fitness trackers like nutrition tracking tools..... Nutrition trackers are really useful if you are starting a new dietary regime to help you understand the macro breakdown of different foods & meals and understand/tweak daily intakes. However after a few weeks of use you should have gained sufficient knowledge that you can  approximate the macro nutrient content of a given  meal and intuitively maintain your dietary targets. 

This blog post was originally going to be a review/comparison of current fitness trackers but I think for now I've talked myself out of the need for one! I'll probably get another device at some point but for now I'm good and instead will pay closer attention to how I feel & perform.