- High cholesterol, or hypercholesterolemia, is a condition in which there are unhealthy high levels of cholesterol in the blood. It is also called dyslipidemia, hyperlipidemia, and lipid disorder.
- Too much cholesterol in the blood is a major risk for heart disease, which may lead to a heart attack, heart failure (cannot pump enough blood to the body), and death. High cholesterol levels are also a risk factor for stroke (lack of blood and oxygen to the brain), causing nerve damage.
- Cholesterol is a soft, waxy, fat-like substance found within the bloodstream and cells of the body. Cholesterol synthesis is a naturally-occurring process that functions to produce membranes for all cells in the body, including those in the brain, nerves, muscles, skin, liver, intestines, and heart. Cholesterol is also converted into steroid hormones, such as the male and female sex hormones (androgens and estrogens) and the adrenal hormones (cortisol, corticosterone, and aldosterone). In the liver, cholesterol is the precursor to bile acids that aid in the digestion of food, especially fats. Cholesterol is also used in making vitamin D.
- The body obtains cholesterol in two ways, producing the majority of it in the body, and consuming the rest in the diet in the form of animal products, such as meats, poultry, fish, eggs, butter, cheese and whole milk. Plant foods, like fruits, vegetables, and grains, do not contain cholesterol. Fat that occurs naturally contains varying amounts of saturated and unsaturated fat.
- High cholesterol can cause the formation and accumulation of plaque deposits in the arteries. Plaque is composed of cholesterol, other fatty substances, fibrous tissue, and calcium, normal substances in the blood that become deposited on the artery walls if the blood does not flow properly. When plaque builds up in the arteries, it results in atherosclerosis (hardening of the arteries), or coronary heart disease (CHD). Atherosclerosis can lead to plaque ruptures and blockages in the arteries, which increase the risk for heart attack, stroke, and death, as well as circulation problems such as Raynaud's disease and high blood pressure.
- The development of plaques and blockages in the arteries involves several steps. When the innermost lining of the arteries (endothelium) is damaged by oxidation, cholesterol particles, proteins and other substances deposit into the damaged wall and form plaques. More cholesterol and other substances incorporate into the plaque and the plaque grows, narrowing the artery. Over time, plaque deposits may grow large enough to interfere with blood flow through the artery (called a blockage). When the arteries supplying the heart with blood (coronary arteries) are blocked, chest pain (angina) may occur; when arteries in the legs are blocked, leg pain or cramping may occur; and when arteries supplying the brain with blood are blocked, stroke may occur.
- The platelets collecting on the plaque deposit are forming a clot as they try to rush by and get caught because the lining of the artery is rough and the platelets are sticky. Then the clot can break off and travel through the body, getting lodged in vessels of the leg or brain and less commonly the lungs. If a plaque ruptures or tears, a blood clot (thrombus) may develop. If a blood clot completely blocks blood flow through a coronary artery, heart attack (myocardial infarction) occurs; if an artery supplying blood to the brain is completely blocked, stroke occurs.
- Blood clots can break loose and travel through the bloodstream (called an embolus) and lodge in blood vessels in other parts of the body, including the lungs, heart, brain, and legs. A thromboembolus is when the blood clot lodges in vessels.
- According to current estimates, 71.3 million people in America have one or more forms of heart disease. High cholesterol affects about 20% of adults over the age of 20 in the United States. The highest prevalence occurs in women between the ages of 65 and 74. The World Health Organization (WHO) reports that high cholesterol contributes to 56% of cases of coronary heart disease worldwide and causes about 4.4 million deaths each year.
- Generally, people who live in countries where blood cholesterol levels are lower, such as Japan, have lower rates of heart disease. Countries with very high cholesterol levels, such as Finland, have very high rates of coronary heart disease. However, some populations with similar total cholesterol levels have very different heart disease rates, suggesting that other factors (such as diet, heredity, and smoking) also influence risk for coronary heart disease.
- Evidence is accumulating that eating more carbohydrates, especially simpler, more refined carbohydrates such as white breads, sugar, and pasta, may increase levels of triglycerides in the blood, lower high density lipoprotein (HDL or "good" cholesterol), and may increase low density lipoprotein (LDL or "bad" cholesterol). Thus a low fat diet, which often means a higher carbohydrate intake, may actually be an unhealthy change.