Cholesterol (HDL / LDL)
An essential fat made mostly by the liver and carried in the blood by lipoproteins (HDL, the so-called "good" one, and LDL, the "bad" one), used to make hormones, vitamin D and cell membranes.
Cholesterol is not a poison: it is a vital molecule. It forms part of cell membranes and is the precursor of steroid hormones (testosterone, oestrogens, cortisol), vitamin D and bile salts.
The body makes about 75% of it itself (in the liver); only about 25% comes from food. Cholesterol travels in the blood via:
- LDL (low-density lipoprotein): carries cholesterol to the tissues. In excess, it oxidises and builds up in the arteries = “bad”
- HDL (high-density lipoprotein): carries cholesterol back to the liver for removal = “good”
A fresh angle: dietary cholesterol (eggs, prawns) has a much smaller effect on blood cholesterol than was once thought. Advice to limit eggs has been dropped in several countries. The body regulates its own production: if you eat more cholesterol, the liver makes less.
The real drivers of high blood cholesterol are refined sugars, trans fats, excess calories and lack of exercise, not eggs.
A finer indicator than total LDL is LDL particle size. Large LDL particles are relatively harmless, while small, dense ones are atherogenic. The triglyceride/HDL ratio is also a better predictor of risk than total cholesterol.