The Role of Diet in Preventing Cardiovascular Disease, a Killer That Starts in Childhood
How common is cardiovascular disease?
Deaths caused by the cardiovascular diseases take an average of fifteen years off of the normal lifespan. Cardiovascular disease kills almost 750,000 Americans every year and accounts for 30 percent of all deaths. Heart attack, also known as a myocardial infarct, is the commonest cardiovascular disease and is the leading cause of death after age 40. Even among young people in their twenties it is one of the top ten causes of death!
What are cardiovascular diseases?
Forms of cardiovascular diseases include impaired ability of the heart to pump blood due to congenital defects, damage to the valves of the heart or disruption of the regularity of the heart’s beat. But most cardiovascular disease results from the complications of atherosclerosis-- also commonly called arteriosclerosis. Atherosclerosis results from the progressive silent accumulation of cholesterol in the walls of arteries that form a plaque that thickens arterial walls. The resultant loss of flexibility, scaring and narrowing of the lumen of the artery cuts down on or even blocks the ability of the vessel to carry blood.
Arteriosclerosis can disrupt and limit the flow of blood to any part of the body. When the blood circulation to the brain is disrupted, either because an artery is blocked or if a damaged artery ruptures and causes bleeding in the brain, the result is a stroke. When the coronary arteries that supply blood to the heart's muscle are narrowed because of a build up of plaque, one result can be chest pain, or angina, when the heart tries to cope with the extra demands of exertion. Atherosclerosis can also cause limited exercise tolerance or heart failure because the heart muscle’s ability to pump blood is weakened by an inadequate oxygen carrying supply of blood or previous damage to the heart’s muscle.
When an unstable plaque in a narrowed coronary artery ruptures into the lumen of the artery, the body may attempt to ‘heal” the break by forming a blood clot, and the clot may block the artery. The sudden loss of blood flow to the heart causes a “heart attack” that weakens the pumping ability of the heart and may cause the death of some of the heart’s muscle. If a heart attack affects large area of the heart, the ability of the heart to pump blood may be so compromised that heart failure or death results. Death can also occur if a heart attack causes a disruption of the electrical signals that coordinate the heart’s pumping action. The result may be irregular uncoordinated heartbeats, called ventricular fibrillation, that prevent the heart from pumping enough blood to sustain life.
Atherosclerosis starts in childhood
Children who eat a typical American diet show the beginning signs of atherosclerosis early in life. The 1992 Bogalusa Heart Study found that children who died in accidents already had fatty streaks and plaques on their arteries—the signs of early atherosclerosis.
In a 1953 study, pathologists examining the coronary arteries of young men (average age 22) who were killed in the Korean War were surprised to find that 77.3% of American soldiers had easily visible evidence of atherosclerosis—and sometimes it was severe. In contrast, the dead Korean and Chinese soldiers who lived on a plant-based diet were virtually free from atherosclerosis. In 1971, similar studies among Vietnam War combat dead, found that 45% of those examined had evidence of coronary atherosclerosis and among 5% the disease was severe.
A more recent study, among U.S. service men who died from unintentional injuries found lower levels of coronary arthrosclerosis. While not entirely comparable to the earlier studies, autopsies carried out between 2001 and 2011 found coronary atherosclerosis of any severity among 8.5% of those studied. It was minimal in 1.5%, moderate in 4.7%, and severe in 2.3%. The low levels of atherosclerosis in the 2012 study may be accounted for by the low levels of risk factors present in this young (average age 27) population compared to the general public. Only 4% were obese, 3% smoked, 1% had high blood pressure, 0.7% had cholesterol levels higher that 240 mg/dl, and 0.2% had high fasting blood glucose levels.
These recent studies of U.S. service men should not be considered a cause for complacency about cardiovascular disease. A high proportion of the older study subjects showed signs of atherosclerosis. Those age 40 or older were seven times more likely to have coronary atherosclerosis than those age 24 and younger. Among those ages 30 to 39 the prevalence of aortic and/or coronary atherosclerosis was 22.1% and among those age 40 or older it was 45.9%.
Another autopsy study of young people in published in 1998 found that the prevalence of fatty streaks in the coronary arteries increased with age from approximately 50 percent at 2 to 15 years of age to 85 percent at 21 to 39 years the prevalence of raised fibrous-plaque lesions in the coronary arteries increase from 8 percent at ages 2 to 15 years to 69 percent at ages 26 to 39.
The progression of cardiovascular disease with advancing age was also documented in the National Health and Nutrition Examination Survey that found that the percentage of Americans with cardiovascular disease progressed with age:
What causes, and how can we prevent heart disease?
It was once thought that progression of atherosclerosis was a “normal” part of aging. But we now know that both the occurrence of atherosclerosis and its progression with age are pathological and can almost completely be avoided through the adoption of a healthy lifestyle.
Elevated blood pressure, elevated blood cholesterol levels and cigarette smoking are the most important risk factors for heart attack and stroke. A healthy diet, not being overweight or obese, and regular physical activity are also important for preservation of cardiovascular health.
The global INTERHEART study identified and studied 9 easily measured risk factors for heart attack. They were found to account for over 90% of the risk of acute myocardial infarction. The risk factors that were identified are mostly lifestyle related: smoking, lipids (cholesterol), hypertension, diabetes, obesity, diet, physical activity, alcohol consumption, and psychosocial factors.
Fortunately many of the most important risk factors for cardiovascular diseases can be modified so as to decrease risk. Modifiable cardiovascular risk factors include:
A single risk factor may contribute to several physiological changes in the body that predispose to cardiovascular disease. For example inadequate exercise may contribute to obesity, elevated blood pressure, and an unhealthy pattern of blood cholesterol--all of which are associated with higher risk of atherosclerotic heart disease
Because the metabolic syndrome is also associated with a generalized metabolic disorder that prevents people from using insulin efficiently, it is also sometimes called the insulin resistance syndrome. Among children the metabolic syndrome is less well defined but it is common. One suggested measure for obesity among children is abdominal circumference over the 90th percentile. To reverse the metabolic syndrome when it occurs among children it is especially important to counter obesity by reducing intake of sugar, especially when consumed in liquid forms as in soft drinks and juices.
A healthy lifestyle can prevent most heart attacks
Almost all heart attacks are preventable when a person adopts a lifestyle that include maintaining a healthy weight and diet, adopting a regular exercise program, avoiding cigarettes and keeping alcohol consumption to a minimum. And starting a healthy lifestyle in childhood maximizes the odds that it will be effective in preventing cardiovascular disease. We know that by modifying the risk factors for cardiovascular disease and lowering cholesterol, atherosclerosis can even be reversed.
Blood lipids—cholesterol and triglycerides
People and populations with favorable blood lipid levels have low rates of cardiovascular disease. Cholesterol is essential for the body’s metabolism; it only causes a problem when there is too much of it in the blood stream. When a person’s diet is healthy, that is that it is low-fat, low in cholesterol, low in added sugars and highly refined foods, and whole-food plant-based, the human body synthesizes appropriate and healthy levels of cholesterol.
Studies have shown that people with total cholesterol levels of less than 150 milligrams per deciliter (mg/dl) have a very low risk coronary artery disease risk. The importance of low cholesterol in prevention of coronary artery disease is also confirmed by studies of people living on low-fat plant-based diets in the poor developing countries in Asia, and Africa. They typically have total-cholesterol levels in the range of 125-140 mg/dl, and they almost never develop coronary artery disease. About 25 percent of the adult population 20 years of age or older have total cholesterol levels of 240 mg/dl or greater and more than twice the heart attack risk of someone whose cholesterol is 200 mg/dl.
For years it was thought, and the public was told, that a blood cholesterol level of 200 mg/dl was normal, of no particular concern to health, or even a desirable level. In fact this level is just an average among Americans with our usual high-risk, unhealthy diet and lifestyle. About 50 percent of adult Americans have blood cholesterol levels of 200 mg/dl or greater which places them at an increased risk for coronary heart disease. In fact, a high proportion of heart attacks occur among men and women with this “normal” supposedly “desirable” cholesterol level. Fully 35% of heart attacks occur among people with blood cholesterol between 150 mg/dl and 200 mg/dl. A low blood cholesterol level is cardio-protective, and a safe level for total cholesterol is 150 mg/dl or lower.
The form of cholesterol most associated with atherosclerosis and risk of heart attack is low-density lipoprotein cholesterol (LDL-C or LDL). Studies show that the attainment of a low LDL-C beginning early in life is associated with a substantially greater reduction in the risk of cardiovascular disease than lowering LDL-C later in life. A goal for the level of LDL-C should be 80 mg/dl or lower and the Coordinating Committee of the National Cholesterol Education Program recommends a LDL-C level of 70 mg/dl or lower for those at high risk of vascular heart disease.
Many people who have heart disease or diabetes have high blood triglyceride levels. Fat deposits in the body are stored in the form of triglycerides. People with a high blood level of triglycerides often have a high total cholesterol level, a high LDL level, a low HDL level, and an elevated risk of heart attack and stroke. A triglyceride level of 150 mg/dL or higher is one of the risk factors the metabolic syndrome that increases the risk for heart disease and diabetes. There is evidence that lowering triglyceride levels results in a lower risk of coronary heart disease events.
High triglycerides are mainly a lifestyle-related risk factor. Many people have high triglyceride levels because of being overweight or obese, low levels of physical activity, cigarette smoking, and excess alcohol consumption. Lowering triglycerides is possible by controlling weight, eating a heart healthy low fat, plant-based diet, getting regular exercise, avoiding tobacco, eliminating alcohol or at least limiting it to one drink per day for women or two drinks per day for men and limiting beverages and foods with added sugars.
Sugars that are added to foods or beverages when they are processed or prepared are not essential and are categorized as added sugars. Added sugars, regardless as to their form, white sugar, high fructose corn syrup, honey or molasses, have the same physiological effects on health. Strong evidence shows associations between excess sugar consumption and obesity, diabetes, and heart disease. High consumption of sugar has also been implicated in the causation of high blood pressure, gout, liver disease and accelerated aging.
Sugar and obesity
It takes 3500 surplus calories to make up one pound of fat and a deficit of 3500 calories to lose a pound of fat. Eating fewer calories than the body needs results in use of stored fat for energy and the body’s metabolism, and results in weight loss. Although this simple formulation of weight gain and loss is generally valid, increasingly research is showing that it matters where you get extra calories. Although the human body can convert surplus calories in the form of each of the macronutrient categories (carbohydrates, proteins, fats and alcohol) into fat, the biochemical pathways for metabolizing dietary fat, alcohol and fructose, (found in almost all forms of added sugar), make it more likely that extra calories from these sources will end up stored as fat.
Sugar and diabetes
Nearly 1 in 10 adults worldwide are now affected by diabetes. Studies implicate excessive sugar intake as an independent cause of high diabetes rates. One important study, compared sugar intake with diabetes prevalence in 175 countries. It found that that independent of body weight, sedentary behavior or alcohol use, sugar intake was associated with the development of type 2 diabetes. The study found that duration and amount of sugar consumption correlated with diabetes prevalence in a dose-response manner. Every 150 calories per person per day increase in sugar availability (about one can of soda/day) was associated with increased diabetes prevalence by 1.1% (p <0.001). The study also found no other food types were associated with diabetes prevalence after controlling for obesity and other factors.
Sugar and heart disease
In another study, researchers looked at the incidence of heart disease and the dietary patterns of nearly 43,000 men participating in the Health Professionals’ Follow-Up Study. After adjustment for age, smoking, physical activity, alcohol, multivitamins, family history, diet quality, energy intake, body mass index, pre-enrollment weight change, and dieting, the study found that participants in the top quartile of sugar-sweetened beverage intake (about 6.5 soft drinks per week), had a 20% higher relative risk of coronary heart disease than those in the bottom quartile. Moreover, those who consumed the greatest amount of sugar-sweetened drinks also had higher triglyceride and C-reactive protein levels and lower HDL cholesterol levels. No increase in the risk of heart disease was found among men who drank artificially sweetened beverages. Other studies have also consistently shown that consumption of sugar-sweetened beverages is associated with weight gain and type 2 diabetes.
How much sugar is too much?
Recommended daily maximum of added sugar for a 2000 calorie per day diet
Preventing and reversing heart disease—the role of nutrition
Since there is no single condition that is associated with all of the increased risk of cardiovascular disease, the best strategy is to simultaneously address multiple risk factors. Those that can be modified to decrease risk include, improper diet, high blood cholesterol, high blood pressure, smoking, diabetes, obesity, alcohol consumption, stress, and lack of exercise. Among these factors high LDL cholesterol, cigarette smoking, high blood pressure, and sedentary lifestyle are the most important. This Timely Topic, addresses ensuring a safe and healthy level of cholesterol through healthy nutrition, other Timely Topics address smoking, physical activity, blood pressure and stroke.
Dean Ornish and Caldwell Esselstyn Jr. are among the physicians who have conducted careful clinical trials that demonstrated that a lifestyle intervention based on diet would usually halt the progression of coronary heart disease and even reverse it. Their, and other studies have shown that although addressing all risk factors is important, a modified diet was among the most powerful single lifestyle change to reduce risk of cardiovascular disease. Their therapeutic intervention is based on a very low-fat diet (ideally about 10% total calories from fat), consuming no saturated or trans-fats, limiting added sugars and refined grains, and eating a diet consisting mainly of natural unrefined plant-based foods including fruits, vegetables, legumes, whole grains, soy and cereals. Their whole-food plant-based diet is high in fiber and low in rapidly absorbed simple sugars so it has a low glycemic index and does not over-stimulate the release of insulin. Dr. Ornish has found that the addition of exercise and stress management additionally improves the outcomes of his lifestyle modification program. Angiograms of Dr. Ornish’s patients showed improved coronary artery blood flow. They demonstrate that heart disease can be reversed without medicines or surgery.
Studies similar to those of Dr. Ornish carried out by Dr. Caldwell Esselstyn Jr. of the Cleveland Clinic Foundation found equally impressive results. In his book Prevent and Reverse Heart Disease, Dr. Esselstyn described patients who, although they were receiving aggressive treatment with surgery and drugs, remained ill with advanced coronary artery disease and were experiencing increasing symptoms such as angina. His goal was to reduce his patient’s total cholesterol levels to those seen in cultures where heart disease is essentially nonexistent. Within a few months of initiating a very low-fat plant-based diet, the study subjects experienced a rapid decline in their cholesterol levels and angina symptoms.
After 5 years on Dr. Esselstyn’s plant-based diet, the average total cholesterol levels of his research subjects declined from 246 mg/dL to 137 mg/dL. Most patients had a repeat of their angiography at 5 years that found that none of the study group had progression of coronary artery stenosis, and 70% had selective regression. All patients who maintained the diet achieved a cholesterol goal of less than 150 mg/dL and had no recurrent cardiac events during a 12-year follow up. And among patients adherent to the program, after twenty years they are still free from heart related symptoms. Dr. Esselstyn’s study showed that a nutrition-based intervention could stop and reverse progression of very severe coronary artery disease. An impressive group of clinicians and researchers advocate the very-low-fat diet and consider it the best. They include Ornish, Esselstyn, Connor, McDougall, Fuhrman, Bernard Campbell, Jenkins, and Shintani. They have had similar results with nutrition based interventions.
The diet that Ornish, Esselstyn and others advocate can be described as follows:
What to eat when on a very-low-fat (VLF) whole-food plant-based diet:
What to avoid when on a very low fat diet:
Mediterranean, mixed, and balanced diets
If a very-low-fat diet is too restrictive to follow, Mediterranean, mixed, and balanced diets should be considered. These three diets are very similar, and they are major improvements over the typical American’s diet. They have been well studied, and they are advocated by many well-respected nutrition experts. They allow for more fat in the diet (in the form of polyunsaturated fats and monounsaturated fats) and a broader variety of foods. They are therefore considered to be more likely to be adhered to. These diets are based on the diets of the Mediterranean region. Mixed and balanced diets are healthier variations of the typical Western diets consumed in the U.S. and other developed countries. They include both plant and animal foods.
The Mediterranean diet includes a range of traditional dietary patterns found in regions that are associated with healthier lifestyle patterns, reduced risk of cardiovascular disease and increased longevity, such as in the Blue Zones (e.g., Ikaria, Greece; Ogliastra Region, Sardinia). Foods that are emphasized include olive oil, vegetables, fruits, nuts and seeds, beans and legumes, selective dairy intake, and whole grains; often fish and other seafood; and quite limited consumption of meat. Consumption of moderate amounts of alcohol in the form of wine is often a feature of the Mediterranean diet.
Mediterranean eating has been associated with reduced risk (but not elimination) of cardiovascular disease, preserved cognition, and possibly evidence for reduced risk of cancer. The Mediterranean diet has been found to have favorable effects on a broad variety of the biomarkers associated with cardiovascular health including, lipoprotein levels, insulin resistance, and metabolic syndrome.
Mixed and balanced diets are diets modified to conform with authoritative dietary guidelines for healthier diets, such as the Dietary Reference Intakes of the Institute of Medicine, the Dietary Guidelines for Americans, and the Dietary Recommendations of the World Health Organization. These authorities generally recommend an emphasis on plant-based foods. They call for increasing the number of servings of fruits to 2 cups/day for a 2400 calorie diet, and vegetables to 3 cups/day for a 2400 calorie diet. A 2013 survey found that fewer than 15% of US citizens had the recommended fruit intake, and 8.9% met the recommendations for vegetables.
The Dietary Approaches to Stop Hypertension (DASH) is a typical mixed and balanced diet. It emphasizes reducing the intake of salt, saturated fat and cholesterol and increased consumption of fruits, vegetables and whole grains and has been shown to lower blood pressure. A DASH diet is even more effective in lowering blood pressure when it is combined with other measures to increase fitness through appropriate levels of physical activity , attain and maintain a healthy weight, and manage stress.
Almost everyone with the typical American lifestyle develops some degree of atherosclerotic cardiovascular disease. So it is important to develop healthy eating habits in childhood and avoid a lifetime of eating an unhealthy diet with large amounts of high sugar, high fat, processed foods. It is also important to avoid the typical American high sodium diet that contributes to high blood pressure. (See Timely Topic Preventing Stroke for more information on hypertension)
A final thought about health advice: often such advice does not call for enough lifestyle change. Modest lifestyle changes will bring about modest gains in health. A healthy lifestyle is not all or nothing, but the further one goes and the healthier your diet, the lower your blood pressure and LDL cholesterol the healthier you will become.
References and Links
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