Coronary heart disease (CHD) is a leading cause of death and disability in Western societies. Both increased plasma low-density lipoprotein (LDL) cholesterol (LDL-C; >160 mg/dL or 4.2 mmol/L) and decreased high- density lipoprotein (HDL) cholesterol (HDL-C; <40 mg/dL or 1.0 mmol/L), along with aging, elevated systolic blood pressure (>140 mm Hg), cigarette smoking, and diabetes (fasting glucose >125 mg/dL), have all been defined as independent risk factors for CHD. CHD is caused by atherosclerosis, a process in which the coronary arteries as well as other arteries become occluded. The characteristics of this process in the artery wall are the presence of cholesterol-laden macrophages or foam cells, proliferation of smooth muscle cells with excess connective tissue, calcification, and sometimes thrombosis as the terminal event occluding the artery. A heart attack or myocardial infarction (MI) occurs when one or more of the three major coronary arteries becomes blocked (1). A stroke occurs when one or more of the arteries supplying the brain becomes occluded. CHD and stroke together are known as cardiovascular disease (CVD), which accounts for about half of all mortality in developed societies including the United States.
Aging, high blood pressure, diabetes, and smoking can all damage the lining of the artery wall. Moreover, LDLs can be deposited in the artery wall, especially at sites of damage. Therefore high levels of LDL-C (>160 mg/dL or 4.2 mmol/L) associated with high total cholesterol values (>240 mg/dL or 6.2 mmol/L) are a significant risk factor for CHD. In addition, HDLs serve to remove cholesterol from the artery wall. Low levels of HDL-C (<40 mg/dL or 1.0 mmol/L) are a significant CHD risk factor (2). Diets high in animal fat, dairy products, eggs, sugar, and salt have been associated with excess obesity, elevated blood cholesterol, and high age-adjusted CHD mortality rates (1). Family history of premature CHD and age are also significant risk factors for CHD (2, 3).
NATIONAL GUIDELINES
United States Dietary Guidelines
Every 5 years, the federal government updates dietary guidelines for the United States. In the 2010 version (4), the following four initial recommendations were made with the goal of preventing chronic disease and promoting health:
Prevent or reduce overweight or obesity through improved eating and physical activity behaviors.
Control total calorie intake to manage body weight. For people who are overweight or obese, this will mean fewer calories from foods and beverages.
Increase physical activity and reduce time spent in sedentary behaviors.
Maintain appropriate calorie balance during each stage of life: childhood, adolescence, adulthood, pregnancy and breast-feeding, and older age.
Dietary guidelines for the general population focus on building long-term eating patterns that promote health maintenance. The guidelines include specific recommendations, which include the following: balancing caloric intake and physical activity to reduce overweight and obesity; restricting sodium to less than 2300 mg/day; reducing saturated fat to less than 10% of calories, with replacement by monounsaturated and polyunsaturated fats, and limiting cholesterol to less than 300 mg/day; restricting intakes of trans-fats, solid fats, sugars, refined grains, and sugars; and limiting consumption of alcohol (no more than one drink per day in women and no more than two drinks per day in men). In those with LDL-C levels higher than 160 mg/dL after ruling out secondary causes, further restriction of saturated fat to less than 7% of calories and cholesterol to less than 200 mg/day is recommended. Additionally, specific foods or food groups to increase or decrease are also recommended for the general population (Table 65.1). Additional guidelines for special groups including pregnant and lactating women and persons more than 50 years old have also been established.
TABLE 65.1 SUMMARY OF UNITED STATES DIETARY GUIDELINES, 2010, RELEVANT TO ATHEROSCLEROSIS PREVENTION IN THE GENERAL POPULATION
Recommendations to prevent chronic disease and promote health
Prevent or reduce overweight or obesity through improved eating and physical activity behaviors.
Control total calorie intake to manage body weight. For people who are overweight or obese, this will mean fewer calories from foods and beverages.
Increase physical activity and reduce time spent in sedentary behaviors.
Maintain appropriate calorie balance during each stage of life: childhood, adolescence, adulthood, pregnancy and breastfeeding, and older age.
Foods to decrease
Reduce daily sodium intake to less than 2,300 mg, and further reduce intake to 1,500 mg in those who are 51 years old and older and those of any age who are African-American or have hypertension, diabetes, or chronic kidney disease. The 1,500-mg recommendation applies to about half of the US population, including children, and the majority of adults.
Consume less than 10% of calories from saturated fat by replacing them with monounsaturated and polyunsaturated fatty acids.
Consume less than 300 mg/day of dietary cholesterol.
Keep trans-fatty acid consumption as low as possible by limiting foods that contain synthetic sources of trans-fats, such as partially hydrogenated oils, and by further limiting solid fats.
Reduce the intake of calories from solid fats and sugars.
Limit the consumption of foods that contain refined grains, especially grain foods that contain solid fats, added sugars, and sodium.
If alcohol is consumed, it should be consumed in moderation—up to one drink per day in women and two drinks per day in men—and only by adults of legal drinking age.
Foods to increase
Increase vegetable and fruit intake.
Eat a variety of vegetables, especially dark green and red and orange vegetables, and beans and peas.
Increase intake of fat-free or low-fat milk and milk products, such as milk, yogurt, cheese, or fortified soy beverages.
Choose a variety of protein foods, which include seafood, lean meat, and poultry, eggs, beans and peas, soy products, and unsalted nuts and seeds.
Increase the amount and variety of seafood consumed by choosing seafood in place of some meat and poultry.
Replace protein foods that are higher in solid fats with choices that are lower in solid fats and calories and/or are sources of oils.
Use oils to replace solid fats where possible.
Choose foods that provide more potassium, fiber, calcium, and vitamin D, which are nutrients of concern in US diets. These foods include vegetables, fruits, whole grains, and milk and milk products.
Data from US Department of Agriculture. Dietary Guidelines for Americans 2010. Available at: www.dietaryguidelines.gov. Accessed June 15, 2012, with permission.
Guidelines of the National Cholesterol Education Program
The National Heart, Lung, and Blood Institute (NHLBI) launched the National Cholesterol Education Program (NCEP) in 1985, with the goal of reducing CHD deaths in the United States by reducing the percentage of US residents with high blood cholesterol levels. The NCEP released three sets of guidelines for treatment of adults, referred to as Adult Treatment Panel (ATP) guidelines, in 1988 (ATP I), 1994 (ATP II), and 2001 (ATP III), with an optional update in 2004 (2, 3). Newer guidelines are expected in 2012. The NCEP recommends that lipids be measured on several occasions after an overnight fast to assess total cholesterol, triglycerides, HDL-C, and calculated LDL-C. Calculated LDL-C is equivalent to total cholesterol minus HDL-C minus triglycerides divided by 5, provided the subject is fasting and triglyceride values are less than 400 mg/dL) (5). The following values have been classified as optimal with regard to CHD risk:
Total cholesterol lower than 200 mg/dL
Triglycerides lower than 150 mg/dL
Non-HDL-C lower than 130 mg/dL
LDL-C lower than 100 mg/dL
HDL-C higher than 50 mg/dL
The following values have been classified as abnormal and are associated with increased CHD risk:
Total cholesterol higher than 240 mg/dL
Triglycerides higher than 150 mg/dL
Non-HDL-C (total cholesterol — HDL-C) higher than 190 mg/dL
LDL-C higher than 160 mg/dL
HDL-C lower than 40 mg/dL in men and lower than 50 mg/dL in women
Before therapy is initiated, secondary causes of lipid abnormalities should be excluded. These causes include the following: diabetes mellitus, hypothyroidism, liver disease, and renal failure; and the use of drugs that increase LDL-C or decrease HDL-C (progestins, anabolic steroids, and corticosteroids). In addition, in patients without CHD or diabetes, the 10-year risk of developing CHD should be calculated using the point system shown in Tables 65.2 and 65.3 or by accessing the NHLBI website (6). Using the website is more accurate because it treats variables continuously rather than with intervals. The point system separates subjects by gender, and then the 10-year risk of developing CHD is estimated from age, total cholesterol, smoking status, HDL-C, and systolic blood pressure.
The ATP III established the following categories of risk and LDL-C goals of therapy in 2001, and these recommendations were modified in 2004 (2, 3), as follows:
High risk: High risk has been defined as having CHD, including a history of MI, unstable or stable angina, coronary artery angioplasty or bypass surgery, or evidence of myocardial ischemia, or having a CHD risk equivalent based on evidence of peripheral vascular disease, abdominal aortic aneurysm, carotid artery disease, stroke, transient ischemic attacks, diabetes, or two or more CHD risk factors and a 10-year risk of hard CHD end points of more than 20% based on the Framingham risk assessment (see Tables 65.2 and 65.3). CHD risk factors have been defined by ATP III as cigarette smoking, hypertension (blood pressure >140/90 mm Hg or the use of antihypertensive medication), low HDL-C (<40 mg/dL), family history of premature heart disease (CHD in a male first-degree relative <55 years old, CHD in a female first-degree relative <65 years old), and age (men >45 years old, women >55 years old). In high-risk patients as defined earlier, the current NCEP ATP III LDL-C goal is less than 100 mg/dL, with an optional goal of less than 70 mg/dL, using both dietary therapy and medications as treatments (2, 3).
Moderately high risk: In subjects with two or more CHD risk factors as listed earlier and a 10-year risk of hard CHD end points of 10% to 20% based on the Framingham risk score (see Tables 65.2 and 65.3), the current NCEP ATP III LDL-C goal is less than 130 mg/dL using both dietary and drug therapy (2, 3).
Moderate risk: In subjects with two or more CHD risk factors as listed earlier and a 10-year risk of hard CHD end points of less than 10% based on the Framingham risk score (see Tables 65.2 and 65.3), the current NCEP ATP III LDL-C goal is less than 130 mg/dL using both dietary and drug therapy (2, 3).
Low risk: In subjects with one or no CHD risk factors as listed earlier and a 10-year risk of hard CHD end points of less than 10% based on the Framingham risk score (see Tables 65.2 and 65.3), the current NCEP ATP III LDL-C goal is less than 160 mg/dL using both dietary and drug therapy (2, 3).
Risk Assessment Methods
As previously mentioned, the Framingham risk assessment score is recommended by NCEP ATP III. Risk can be calculated electronically by accessing the NHLBI website (6) or by using the point system provided in the guidelines and found in Tables 65.2 and 65.3 (2). An alternative is the Reynolds Risk Score, which incorporates the same risk factors as the Framingham score and also includes family history of CHD before age 60 years and levels of C-reactive protein (CRP). This score can be accessed at the Reynolds Risk Score website (7), and it is based on two large population studies (8, 9). Another option used by some physicians is to assess the cardiac calcium score, a 30-second test performed using computed tomography (10). This test provides clear information about the presence of calcified plaque in the coronary arteries; the cardiac calcium score is the most powerful available CHD risk factor (10). Most physicians do not actually calculate risk assessment by these methods, but they often use their own clinical judgment about whether any form of therapy (lifestyle and medication) is indicated. This approach often causes physicians to overtreat low-risk patients and undertreat high-risk patients.
Therapeutic Lifestyle Changes Diet
The cornerstone of therapy to help patients achieve their LDL-C goal remains lifestyle modification. For the general population, the NCEP recommended a diet containing less than 10% of calories as saturated fat and less than 300 mg/day of dietary cholesterol (2). For those with elevated total cholesterol levels (especially >240 mg/ dL with an LDL-C value >160 mg/dL), greater change is needed, and the recommended therapeutic lifestyle changes (TLC) of the NCEP ATP III are more stringent, as listed in Table 65.4. If after 6 weeks of dietary modification the LDL-C goal has not been achieved, ATP III recommended the addition of stanol or sterol margarine (two servings per day) and/or viscous fiber.
TABLE 65.2 FRAMINGHAM POINT SYSTEM TO ASSESS 10-YEAR RISK OF CORONARY HEART DISEASE IN MEN
a Risk assessment is based on the point total derived from points for each category.
Data from Expert Panel. Executive summary of the third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 2001;285:2486-97, with permission.
TABLE 65.3 FRAMINGHAM POINT SYSTEM TO ASSESS 10-YEAR RISK OF CORONARY HEART DISEASE IN WOMEN
a Risk assessment is based on the point total derived from points for each category.
Data from Expert Panel. Executive summary of the third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 2001;285:2486-97, with permission.
TABLE 65.4 THERAPEUTIC LIFESTYLE CHANGES GUIDELINES FROM THE NATIONAL CHOLESTEROL EDUCATION PROGRAM ADULT TREATMENT PANEL III FOR PERSONS WITH ELEVATED TOTAL CHOLESTEROL LEVELSa
Balance energy intake and expenditure to maintain desirable body weight and prevent weight gain
aEspecially >240 mg/dL with a low-density lipoprotein (LDL) cholesterol value >160 mg/dL.
b Trans-fat, another LDL-raising fat, should be kept at a low intake.
c Carbohydrate should be derived predominantly from foods rich in complex carbohydrates including grains, especially whole grains, fruits, and vegetables.
d Daily energy expenditure should include at least moderate physical activity (contributing approximately 200 kcal/day).
Data from Expert Panel. Executive summary of the third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 2001;285:2486-97, with permission.
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Jul 27, 2016 | Posted by drzezo in PUBLIC HEALTH AND EPIDEMIOLOGY | Comments Off on Nutrition in the Prevention of Coronary Heart Disease and the Management of Lipoprotein Disorders1
