High blood cholesterol and heart attack
Cholesterol is a complex fatty substance produced by liver for various functions in the body. The amount of cholesterol in our food also contributes to the cholesterol level in blood. If we take excess amount of cholesterol rich food it well predisposes us to increased risk of heart attack. Any excess of cholesterol results in the deposition of cholesterol in the arteries resulting in narrowing and hardening of the arteries (atherosclerosis). When the narrowing of the artery becomes severe enough to result in insufficient blood supply to the heart, chest pain (angina) occurs. The chest pain usually occurs on exertion and is usually relieved by rest. When the artery is completely blocked, the portion of the heart muscle supplied by the artery will be damaged, resulting in heart attack.Basic research and evidence from observational studies and clinical trials have shown a consistent positive relation between the blood cholesterol level and the risk of heart attack. Recent overviews have indicated that a I percent reduction in a person’s total blood cholesterol level yields a 2 to 3 percent reduction in the risk of coronary heart disease. The seven countries study found that coronary artery disease was less common in Japan and Mediterranean countries (where the average diet is low in cholesterol and saturated fat) than in the United States. Finland and Netherlands (where the cholesterol and saturated fat content of average diet is higher). In the United States, the Framingham Heart Study and more recently the Multiple Risk Factor Intervention Trial (MRFIT) have shown that the incidence of coronary artery disease is positively associated with blood cholesterol levels in a continuous, graded and progressive manner. By reducing the blood cholesterol level to normal the risk of heart attack can be decreased by 23%. In the Oslo study the smoking cessation and cholesterol lowering resulted in 47% reduction of heart attack and sudden death compared to control.
Cholesterol in blood is carried in two main forms, low density lipoprotein (LDL) and high density Lipoprotein (HDL). LDL is called bad cholesterol and HDL is called good cholesterol. High LDL cholesterol is associated with atherosclerosis (blockage of coronary artery). HDL cholesterol or good cholesterol removes excess bad cholesterol from the arteries. It is good for the HDL cholesterol to be high and the LDL cholesterol to be low. The role of another blood lipid, triglyceride in producing heart disease independently is questionable. But a recently published study, Helsinki Heart Study documented an inverse relation between elevated triglycerides and low level of HDL that may be reversed with treatment by Gemfibrozil.
The public health effect of the National Cholesterol Education Program’s guidelines is great. Their aim is to lower mean blood cholesterol levels to less than 200 mg% (5.2 mmol per liter), primarily by decreasing the total fat content of the diet to below 30% of total calories and saturated fat to below 10%. The HDL level is to be kept above 55 mg%. A mean 11% increase in the level of HDL cholesterol (good cholesterol) corresponded to a 34% decrease in the incidence of coronary heart disease.
