What is the role of diet in heart disease?
In recent years, medical researchers have documented the important role that diet plays in the prevention and treatment of heart disease. At least four major cardiovascular risk factors are related to diet: high blood cholesterol, high blood pressure, diabetes, and obesity. Thus, the preventive goals of a "heart healthy" diet are to:
- Lower high serum cholesterol levels.
- Control blood pressure.
- Maintain normal blood glucose levels in diabetes.
- Maintain ideal weight.
Of these four factors, cholesterol has been the focus of increasing public awareness. Cholesterol is a fatty
substance (lipid) that circulates in the blood and is present in all animal products.
Although cholesterol is found
in all animal products, egg
yolks, dairy products, and organ meats are particularly high in the substance. In addition, cholesterol is manufactured in the liver and certain cells of the body.
Although cholesterol is essential to life, it creates a health hazard when too much circulates in the blood. For example, high levels of blood cholesterol can lead to atherosclerosis, the buildup of fatty deposits in the arteries. The coronary arteries, which supply blood to the heart muscle, are particularly vulnerable to atherosclerosis. In fact, coronary atherosclerosis is the major cause of heart attacks in the U.S. and other industrialized countries. To reduce the risk of a heart attack, the National Cholesterol Education Program (NCEP) recommends that adults maintain serum cholesterol levels of 200 or lower. Diet remains the safest means of lowering blood cholesterol. Even when a cholesterol-lowering medication is prescribed, it should
supplement, not replace, a heart-healthy diet.
High blood pressure readings consistently above 140/85-90 increase the risk of heart attack, stroke, and kidney failure. The American Heart Association estimates that about 66 million Americans have high blood pressure. Many studies show that reducing high blood pressure lowers the risk of heart disease.
Diet plays an important role in the overall treatment of high blood pressure. One of the first measures physicians recommend to help lower blood pressure is a reduction of salt in the diet.
Sodium — which along with chloride makes up ordinary table salt — promotes the retention of fluid in the body. This results in an increased volume of blood, which requires a rise in blood pressure to circulate through the body. Sodium also interacts with other body chemicals to raise blood pressure.
The exact role of sodium in initiating high blood pressure is unknown, but many doctors recommend that all Americans use salt in moderation. The American Heart Association maintains that if everyone reduced his or her salt intake, many cases of hypertension, which can lead to a heart attack or stroke, could be prevented.
High levels of blood glucose have also been linked to an increased risk of heart disease.
In diabetes, the body is unable to properly metabolize food (especially carbohydrates), due either to a lack of or inability to use insulin. This results in high levels of blood glucose. People with diabetes are particularly susceptible to several forms of heart disease, including atherosclerosis, heart attack, and high blood pressure.
Maintaining normal levels of blood glucose is instrumental in preventing complications of diabetes, including the increased susceptibility to heart disease. Dietary measures to achieve this goal include weight control and, depending upon the type of diabetes involved, following specific meal plans.
Excessive weight contributes to a number of cardiovascular risk factors, especially high blood pressure, high cholesterol, and diabetes. In addition, some studies, including the 40-year Framingham Heart Study, have found that obesity is itself a risk factor for a heart attack.
When should I begin a heart-healthy diet?
If you have been diagnosed as having any form of heart disease, you should consider altering your diet as part of an overall treatment program. You also should consider adopting a prudent or "heart healthy" diet if you fall into a high-risk group for a heart attack; for example, if you have a strong family history of heart disease.