ApoB

Apolipoprotein B, apoB for short, is the structural protein of the particles that bring cholesterol from the liver to the tissues: LDL, its precursors VLDL and IDL, and Lp(a). The protein forms the outside of the particle and is at the same time the key by which cells recognise and take it up. Each of those particles carries exactly one apoB. Your apoB value therefore counts the number of particles that can carry cholesterol into the artery wall, while LDL cholesterol weighs the cargo they carry. That difference matters. Atherosclerosis begins with particles that get stuck in the artery wall, and how many particles there are says more about that than how much cholesterol they carry between them. Two people with the same LDL can have a different apoB: someone with many small, dense particles, as with belly fat and insulin resistance, has more particles than the LDL number suggests, and it is exactly those small particles that enter the artery wall easily. Your report shows apoB as one number in grams per litre (g/L). Labs publish a measured range for it; where those ranges overlap it runs from 0.66 to 1.33 g/L in men and 0.60 to 1.17 g/L in women, and outside that they differ. The table further down shows them side by side.

ApoB is the sharpest single measure of how many harmful particles circulate in your blood, and so of your risk of atherosclerosis. It is most useful where LDL falls short: with high triglycerides, belly fat, insulin resistance or diabetes, where the particles are small and numerous and the LDL number looks more reassuring than it is. In some people, especially with belly fat, LDL and apoB diverge: the LDL says fine, while the number of particles is high. Doctors call that discordance, and it is exactly the group that LDL alone misses. For anyone who wants to stay healthy that is the value of the number: a normal LDL with a raised apoB is an early sign that the metabolism is moving the wrong way, and that direction can be turned with food and exercise. In Dutch practice apoB is not measured routinely, because non-HDL cholesterol, your total cholesterol minus your HDL, gives comparable information without an extra test. ApoB is the sharper addition for anyone who wants to know precisely.

A high apoB means many particles that can carry cholesterol into the artery wall. The causes are the same as for LDL: plenty of saturated fat, excess weight and little exercise, inheritance, an underactive thyroid, and rarely a kidney disease or inherited hypercholesterolaemia. With excess weight and insulin resistance, apoB often climbs further than LDL, because the particles become smaller and more numerous. A low apoB is favourable; there is no lower limit below which something is wrong. In anyone who eats plant-based and fibre-rich, is lean and exercises a lot, it is the ordinary outcome; in others it is inheritance or the effect of cholesterol-lowering medication. The levers are the same as for LDL: olive oil instead of butter, nuts and oily fish instead of fatty meat and processed meat, fibre from oats, legumes, vegetables and fruit, losing weight around the middle and moving every day. ApoB responds to that more strongly than LDL once your waist moves with it, because you then get not only less cholesterol per particle but also fewer particles. For most people without an inherited condition that is the whole solution; with an inherited high cholesterol or existing cardiovascular disease, lifestyle remains the foundation and medication usually joins it. Read apoB beside your LDL: if apoB is higher than the LDL suggests, you have many small particles and your waist is the lever. Look at the overlap of the lab ranges, because they differ, and at the trend across several measurements. The only apoB figure in the Dutch guideline is a signal limit: above 1.0 g/L a non-fasting value stands out. That is not a target.