What is a healthy cholesterol level and when should I be concerned?

Cholesterol is essential for cell membranes, hormones and nerve tissue. Most attention goes to LDL ('bad') and HDL ('good'), but there is a third fraction that is often overlooked: remnant cholesterol. This is calculated as total cholesterol minus LDL minus HDL. Research in humans shows that it is an independent risk factor for atherosclerosis, even when your LDL is normal.

Concretely: people with a normal LDL but an elevated remnant cholesterol had their carotid artery wall thickened almost twice as often, an early sign of atherosclerosis¹. A normal LDL figure on your blood test therefore does not tell the whole story.

In addition to the amount of cholesterol, how your body transports it also matters. The genetic variant APOE4, which increases the risk of Alzheimer's disease, clears cholesterol from brain cells less efficiently. In cell studies, this leads to an accumulation of cholesterol and higher levels of proteins associated with Alzheimer's disease². This is cell research, not evidence in humans. If you have a family history of Alzheimer's disease or carry APOE4, that is an additional reason to discuss this with your doctor.

In mouse studies on ALS, an excess of cholesterol in the nervous system led to poor protection of nerve fibres. Treatment with a cholesterol-binding agent extended lifespan in female but not male mice³. It was also found that immune cells tasked with clearing cancer cells have a cholesterol deficiency, while tumour cells themselves are cholesterol-rich⁴. Neither finding has yet been translated into treatments in humans.

The evidence for a link between cholesterol and anxiety or depression is extremely thin. In a study of 85 patients with panic attacks, anxiety disorder or depression, no meaningful differences in total cholesterol were found⁵. This is therefore not something you need to worry about.