What happens in your body that turns foods that are supposed to help nourish into a potential threat instead? Here’s a brief explanation of how the cholesterol in your body affects the well-being of your heart. This science forms the basis for our recommendations on how to eat better for better health.
Your body needs some cholesterol—a waxy fatlike substance—to strengthen cell walls and for other body functions, such as producing hormones. Your blood carries cholesterol and other fats through your body in distinct particles called lipoproteins. (Because lipids, or fats, do not mix with water, the body wraps them in protein to move them through the bloodstream.) Three types of lipoprotein make up the major part of your total blood cholesterol measurement: low-density lipoprotein (LDL), high-density lipoprotein (HDL), and very-low-density lipoprotein (VLDL).
Ongoing research continues to clarify how the different lipoproteins work in the body. LDL lipoproteins carry cholesterol to the inner walls of the arteries, where it can collect and contribute to the buildup of plaque. That process is called atherosclerosis. Plaque buildup narrows the artery walls and reduces the flow of blood. If a plaque ruptures, it triggers a blood clot to form. If the clot forms where the plaque is, it can block blood flow or break off and travel to another part of the body. If blood flow to an artery that feeds the heart is blocked, it causes a heart attack. If the blockage occurs in an artery that feeds the brain, it causes a stroke. On the other hand, HDL lipoproteins may prevent cholesterol from collecting by carrying it away from the arteries.
In most people, LDL cholesterol makes up 60 to 70 percent of total blood cholesterol. A very clear relationship exists between LDL cholesterol level and risk of heart disease: The higher the level, the greater the risk. This is why LDL cholesterol is the primary target of efforts to lower cholesterol.
The optimal level for LDL cholesterol is less than 100 milligrams per deciliter (mg/dL). Near optimal/above optimal is between 100 and 129 mg/dL. An LDL level between 130 and 159 mg/dL is considered a borderline high risk. If your LDL cholesterol is between 160 and 189 mg/dL, you are at high risk for heart disease. LDL cholesterol that is 190 mg/dL or above is considered very high.
Typically, one-third to one-fourth of the cholesterol in your blood is carried in HDL cholesterol. HDL is considered the “good” cholesterol because an HDL cholesterol level of 60 mg/dL or higher may offer some protection against heart disease. The mean level of HDL cholesterol for American adults age 20 years and older is just over 51 mg/dL.
Strong evidence indicates that low HDL levels (less than 40 mg/dL for men, less than 50 mg/dL for women) are directly related to higher risk for heart disease. Low levels of HDL cholesterol can be caused by many factors. The most common are smoking, overweight and obesity, and lack of exercise. Fortunately, you can change all these factors to increase your HDL level and reduce your risk of heart disease.
Another type of lipoprotein that carries blood cholesterol is very-low-density lipoprotein. VLDLs also carry most of the blood triglycerides. Triglycerides are other lipids found in the blood, as well as in the body’s fat tissue. In fact, triglycerides make up most body fat. Fats found in foods—such as butter, margarine, and vegetable oil—are also triglycerides. As blood circulates, triglycerides are removed from VLDLs to be used for energy by cells or stored as body fat. The remaining lipoprotein particles are called VLDL remnants. These remnants can be taken up by the liver or transformed into low-density lipoprotein. Elevated VLDL cholesterol levels signal the potential need for cholesterol-lowering therapy.
High blood levels of triglycerides are associated with increased risk for heart disease. This is especially true when other risk factors, such as overweight and obesity, smoking, hypertension, diabetes, and low HDL cholesterol, are present.
Scientists continue to explore the complex biochemistry behind the relationship between diet and health. The American Heart Association funds important research that helps us all learn more about how diet impacts heart health. Thanks to the investment in this type of research over the years, the American Heart Association is able to make diet and lifestyle recommendations as a strategy to reduce the risk of cardiovascular diseases. As we publish the fourth edition of this cookbook, current studies are investigating topics such as the effects of various vitamin supplements in patients with stroke and heart failure, as well as how eating behaviors relate to risk factors such as obesity, high cholesterol, and high blood pressure. Other research projects are studying the mechanisms of how foods such as soy and fish might provide protection against risk, and how social interactions affect our eating behaviors. For more information on the latest findings in this constantly evolving field, visit americanheart.org.