Understanding your lipid profile. Is cholestrol really bad? Should one look at Total Cholestrol or HDL or LDL or TG? What really matters?

Cholesterol is essential to life. It is a waxy, fat like substance found in all cells of the body. Some of the most important structures in the body such as cell membranes need cholesterol. It gives the flexibility and stability to the walls of the cells that form our body. It is the most important ingredient for making hormones such as testosterone, progesterone and estrogen. Body also needs cholesterol to convert sunlight into Vitamin D. Cholesterol also helps the liver produce the bile acids needed for digestion

The liver creates most of the cholesterol in the body. So, even if you consume zero sugar and zero fat, the body will still produce cholestrol. It is a non negotiable requirement of life.

Cholesterol, however, is not water soluble and hence cannot be dissolved in our blood plasma like glucose and travel through our system. So it needs carriers in the form of tiny spherical particles called lipoproteins - high density lipoproteins which is the HDL and the low density lipoproteins which is the LDL. Each lipoprotein particle is in turn wrapped in apolipoproteins. HDLs are wrapped in apolipoprotein A (apoA) while LDLs in apolipoprotein B (apoB).

While cholesterol is the building material, triglycerides (TGs) are pure energy. Whenever we consume anything, the excess is converted into TGs by the liver. TGs are the most efficient way to store energy. So even if the diet is low in fats or carbs, liver will still create the essential cholesterol from proteins and it will create TGs to provide energy to cells when they need. Liver is the body’s ultimate survivalist after all.

The liver initially creates a very low density lipoprotein particle (VLDL) - a large, fluffy particle which mostly contains TGs and a little bit of cholesterol. The job of the particle is to drop off the TG in our muscles for consumption or in fat cells for storage. Once the TGs get offloaded, the VLDL becomes more dense and becomes LDL which now mostly contains cholesterol. It moves around looking for cells that need the essential building material which is cholesterol and find its way back to the liver. The liver has LDL receptors which are constantly scanning the blood for these particles wrapped in apoB. If the liver’s receptors are active and healthy, they grab the LDL and pull it back inside. The liver breaks it down. The cholesterol isn't wasted; it's either used to make bile acids or recycled to create more VLDL. This LDL is the particle which eventually can get stuck in the walls of the arteries and cause atherosclerosis if it does not find receptors.

At the same time, liver also produces a particle apoA which is empty when it is created but it is a hungry protein looking for cholesterol. As it fills up, it matures into a sphere which is what we know as HDL. It picks up this excess and returns the same to the liver where it gets broken down and again recycled

How to understand your lipid profile:

TGs: The triglycerides in your blood report essentially tell you the TGs that are in circulation at a given point in time inside the VLDLs. It does not tell you how much more is stored as fat anyway and not yet in circulation. If you have high TGs it means that your body does not need more stored fat and you are dumping too much sugar / fat in the system.

HDL by itself has little meaning (high HDL alone does not imply low cardiac risk and low HDL alone also does not increase the cardiac risk) but we need HDLs to trap the excess cholesterol left behind after the TG are dumped in cells by the VLDL. Hence a ratio of TG / HDL tells us if there are enough HDLs vs. the TGs. A 1:1 ratio is generally considered great. However, if TG are high and HDL is low, it implies, you have more LDL particles or apoB and those particles are not getting cleared by LDL receptors or HDL and can lead to plaque formation.

In summary, you can have a high LDL, but if your TG/HDL ratio is lower than 1, your LDL is likely composed of large, harmless particles, and your risk is actually quite low. Conversely, you can have low LDL, but if your TG/HDL ratio is high, those few LDL particles are likely tiny, dense, and extremely aggressive at forming plaque.

Recent research also suggests that it is not about the amount of cholesterol which is the LDL inside the particle but the number of particles itself that cause the damage and hence many cardiologists believe apoB which is the carrier of LDL is a much stronger predictor of cardiac risk than LDL itself. If you have high apoB it means there are too many LDL particles.

Hence, another very strong indicator of a good lipid function is the apoB/apoA ratio which measures the actual number of particles that cause plaque vs those that clean up plaque. Every single particle that can cause plaque—VLDL or LDL—has exactly one ApoB molecule on it. Every HDL is built around apoA. Measuring this tells you how many active cleanup molecules you have in circulation.

A Ratio of 1.0 indicates you have an equal number of "plaque-makers" and "plaque-cleaners." This is okay, but not ideal. If you strive for a ratio of 0.5, you have two cleanup molecules for every bad one which makes is very difficult for plaque to build up and the risk of atherosclerosis

Next time you get a lipid profile done, do add the apoB and apoA markers on your report