Illustration of a syringe needle sampling blood products, including the low-density lipoprotein (LDL) particle, a form of blood cholesterol. Red blood cells (erythrocytes) are being drawn into the needle together with larger white blood cells (leucocytes), and numerous yellow LDL particles. LDL particles are complex structures consisting of a protein-phospholipid-cholesterol coat, within which more cholesterol molecules are bound to fatty acids. Cardio-vascular research has shown that LDL particles, when occurring in high levels in the blood, lead to an increased risk of narrowing of the arteries (atherosclerosis), coronary heart disease and stroke.