Spotlight B: Lipids in Health and Disease

Plaque

As a result of artery wall inflammation, the lining of the blood vessel becomes more prone to develop a waxy accumulation of cholesterol and triglycerides, known as a plaque. Over time, plaque development, loss of elasticity, and thickening in the blood vessel walls may make it difficult for blood to flow through the vessel. This "traffic jam" increases the chances of forming blood clots that either block flow at that location or break off and travel through the bloodstream, blocking blood flow elsewhere, causing tissue damage and tissue death.

Atherocsclerosis

Atherosclerosis is an inflammatory disease characterized by the accumulation of fatty plaque in the walls of arteries and blood vessels that generally develops over the course of several decades. This process is typically caused by the presence of elevated levels of cholesterol-rich low-density lipoproteins (LDLs) in the blood. As blood levels of LDL rise, they infiltrate the artery wall, where the LDLs are likely to become oxidized (by reacting with unstable oxygen-containing molecules). Oxidized LDLs cause injury to cells that line the vessel wall, and this initiates an inflammatory process that attracts white blood cells called macrophages inside the arterial lining. Other factors, such as smoking and hypertension, can also cause injury to the arterial wall and trigger inflammation. Inside the vessel wall, macrophages take up the oxidized LDLs in a rapid and uncontrolled fashion. These fat-laden macrophages (now called foam cells) die and deposit their accumulated lipids within the wall of the artery, promoting further inflammation.

What is the best overall strategy to protect your heart health?

Based on current evidence, the best overall strategy to protect your heart health is to replace saturated fatty acids with unsaturated ones and to emphasize vegetables, fruits, and whole grains in the diet. (INFOGRAPHIC B.8) The Dietary Guidelines for Americans recommend limiting overall saturated fat intake to 10% or less of total daily calories. - In contrast to earlier editions, the 2015 Guidelines do not establish specific limits for dietary cholesterol, but qualify that eating as little as possible is advisable within a healthy eating pattern. - For those with increased risk for heart disease and high blood cholesterol levels, recommendations from the National Cholesterol Education Program (NCEP) of the National Institutes of Health are to keep calories from saturated fat under 7%.

Effects of a ratio of omega-6 and omega-3 fatty acids in a Western Diet

Everyone's diet contains a ratio of omega-6 and omega-3 fatty acids. Most Americans, and others who follow a Western diet, eat much more omega-6 fatty acids than omega-3 fatty acids, with a typical ratio of 10:1. It has long been argued that lowering this ratio, (such as to 5:1 or 4:1) would improve our health, but recent evidence raises significant questions regarding the general recommendation as high intakes of linoleic acid are associated with a significant reduction in the risk of heart disease. Although our knowledge of the health implications of the consumption of specific types of fatty acids is not complete by any means, for some dietary fats, the effect on health is clear.

Young People and Heart Health

For the most part, young people do not have heart attacks (and those who do usually suffer from rare genetic conditions). But just because most teenagers do not die from heart disease does not mean they can ignore heart health. That's because heart disease can be insidiously gaining a foothold long before a person has any obvious symptoms. A recent study found that nearly 25% of young adults aged 18-24 had at least one advanced atherosclerotic plaque

HDL Cholesterol on Heart health

HDLs, in contrast, bring cholesterol from tissues back to the liver, where it is processed and eliminated. Not surprisingly, low levels of HDL-C—less than 40 mg/dl in men and 50 mg/dl in women—are associated with an increased risk of CVD. Conversely, higher levels of HDL-C can be associated with a lower risk of heart disease, but only up to a value of about 60 mg/dl. So higher levels of HDL cholesterol have a limited ability to offset the risk of heart disease seen with increasing levels of LDL cholesterol. For this reason, calculating the ratio of LDL-C to HDL-C is not clinically useful, particularly in individuals with high LDL-C concentrations.

How did Berenson begin to study young individuals for his CVD studies?

He decided to follow children and young people aged 5-17 years in the local school system, monitoring them twice yearly. Nurses measured their height, weight, smoking history, blood pressure, and blood lipid levels, among other variables. After age 17, they returned for evaluation periodically, up to age 45. Later, it was decided that any of the study participants who died would be autopsied. From small beginnings, the study grew to enroll some 16,000 individuals. It is now one of the longest-running CVD studies in the world, the only one with a biracial (black-white) study population. Known as the Bogalusa Heart Study, it was the first study to demonstrate that heart disease begins in childhood. Although the exact cause of CVD is often unknown, the Bogalusa study has shown that certain risk factors increase young people's chances of developing heart disease—and the more risk factors they have, the higher their chances

Effects of High Fat diets on obesity

High-fat diets may increase the risk of obesity, although that idea remains somewhat controversial. Fat is calorie-dense, and any extra is more likely to be stored as body fat than excess protein or carbohydrate. Obesity is a particular problem in Louisiana, which is one of a series of states (those located between Texas and Florida) that epidemiologists refer to as the "diabetes belt," "stroke belt," or "obesity belt." For some reason—no one knows exactly why—CVD seems to cluster in this region.

Metabolic Syndrome

In general, the risk for CVD increases with the number of risk factors you have. People who are carrying around a cluster of some of the most dangerous risk factors for CVD are said to have metabolic syndrome. For example, having an elevated blood glucose level is a serious condition, but when coupled with excessive amounts of abdominal fat and high blood pressure, a person has a greater chance of cardiovascular problems because of the combination of risk factors. Not surprisingly, this makes them much more likely to have a heart attack or stroke and five times more likely to develop type 2 diabetes.

Low-fat diets high in carbohydrates and CVD

Low-fat diets high in carbohydrates, particularly when low in fiber and high in sugar, actually increase triglyceride levels in the blood. And some recent analyses even suggest that certain sources of saturated fatty acids long thought to be contributors to CVD, such as those in dairy products, actually may not affect blood lipids levels or increase the risk of CVD as negatively as other sources.

Effects of High Fat diets on cancer

Many studies have shown that people who eat high-fat diets, particularly diets high in animal fats, are more likely to develop cancer. Indeed, more than 30% of cancers in adults could be delayed or even prevented by eating a healthy diet, exercising regularly, and maintaining a healthy weight. Not surprisingly, a heart-healthy diet also protects against cancer. Specifically, a diet rich in plant-based foods (such as fruits and vegetables), whole grains, and fish appears to be protective, whereas a diet with few servings of fruits and vegetables and extra portions of processed meat, sodium, alcohol, refined carbohydrates, and high amounts of total fat have the opposite effect. Diet is one of the biggest risk factors for many diseases—including cancer—over which we have some control. Naturally, watching your calorie intake and having a healthy body weight also help.

Modifiable risk factors

Modifiable risk factors include smoking; a diet high in saturated and trans fats, cholesterol, sodium, and added sugar; a sedentary lifestyle; obesity; excessive alcohol consumption; and high blood pressure. (INFOGRAPHIC B.4) Having high blood pressure (hypertension)—a condition in which blood pushes with excessive force against artery walls—is correlated closely with the extent of atherosclerosis found in the arteries.

What causes strokes?

Most cases of stroke result when a clot impairs the supply of blood to the brain.

Therapeutic Lifestyle Changes (TLC)

NCEP created the Therapeutic Lifestyle Changes (TLC) program, which incorporates diet, physical activity, and weight management to lower blood cholesterol levels and reduce the risk of heart disease. Also endorsed by the American Heart Association, the TLC dietary component focuses on lowering saturated fat and dietary cholesterol along with other heart-healthy strategies, such as eating foods that have added plant sterols and stanols and contain sufficient soluble fiber.

What did Berenson and his Bogalusa study team use to evaluate healthy diets?

One of the most important tools Berenson and his Bogalusa study team used to evaluate healthy diets was children's intake of fat and cholesterol. Besides asking children about their diets, the Bogalusa researchers also directly measured levels of lipids in their blood by looking at the lipoproteins that transport lipids around the body. Likewise, physicians use a diagnostic test called a lipid panel to provide information about levels of triglycerides, total cholesterol, and cholesterol in high-density lipoproteins (HDL-C) and low-density lipoproteins (LDL-C) in blood.

What results occur when replacing saturated fats with monosaturated fatty acids?

Research also indicates that replacing saturated fats with monounsaturated fatty acids can improve blood lipid profiles and reduce the risk of heart disease, but not as effectively as what is seen when saturated fats are replaced with polyunsaturated fatty acids. Also, you can get too much of a good thing—there is no consistent rationale or recommendation for the specific amount of monounsaturated fatty acids we should obtain from our diets, but the American Heart Association suggests that people get no more than 25-35% of their total calories from fat, most of which should come from unsaturated fatty acids, and that saturated fat not exceed 7% of total calories.

omega-3 fatty acids

Some research suggests that omega-3 fatty acids may hold particular health benefits, but the picture remains somewhat unclear. For example, as we learned in Chapter 5, low levels of the omega-3 docosahexaenoic acid (DHA) in the diet are associated with an increase in the risk of Alzheimer disease and other forms of dementia, and higher intakes of oily fish are consistently associated with reduced risk of dementia. It's unclear, however, whether fish oil supplements containing DHA and eicosapentaenoic acid (EPA), another omega-3 fatty acid, hold any benefits relative to the risk of dementia.

LDL Cholesterol on Heart health

The LDLs ferry cholesterol to all of the cells of the body. This cholesterol forms the root of the plaques that slowly constrict blood flow through the vessels that feed the heart and brain; the lower your LDL cholesterol level, the lower your risk of heart attack and stroke. If you have other risk factors for CVD, it's best to keep your LDL-C concentration below 100 mg/dl. (Some experts recommend levels closer to 70 mg/dl especially if other risk factors are present.) In some cases, diet and exercise may not suffice, in which case people also take medications that lower their total cholesterol and LDL-C concentrations.

What results were revealed in the Nurses' Health Study?

The Nurses' Health Study, for instance, has followed more than 120,000 women since 1976, looking for links between their diets and lifestyles and their risks of various diseases. When the researchers examined women's fat intake, they found that women who ate the most polyunsaturated fatty acids were least likely to develop heart disease.

How are diagnosis for metabolic syndromes given?

To be given a diagnosis of metabolic syndrome, individuals must have at least three of the following problems: excessive abdominal fat, high blood pressure, elevated levels of triglycerides in the blood, low levels of HDL, and elevated blood glucose levels (either prediabetes or type 2 diabetes—refer to Spotlight A). Furthermore, the prevalence of metabolic syndrome is on the rise. Today, it affects more than 50 million adults in the United States and approximately 25% of adults worldwide

Effects of trans fats

Trans fatty acids are a case in point. They were added to foods to help lengthen shelf life and were often found in many commercial cakes, cookies, pies, and pastries. Responding to the weight of evidence of increased risk of CVD, the FDA banned addition of trans fats to foods in 2018. (Refer to Chapter 5.) Trans fats were found to raise LDL-C and lower HDL-C, along with raising total cholesterol levels. In the Nurses' Health Study, women who ate diets high in trans fats had a significantly higher risk of heart disease.

Examples of Heart Healthy fats in food

Unsalted peanuts and some tree nuts, specifically walnuts, almonds, pecans, and pistachios, are particularly beneficial, and eating at least 5 ounces per week (roughly 900 calories) is consistently associated with a lower risk of heart disease. As long as you don't add nuts to the foods you're already eating—thereby increasing your fat and calorie intake—they are a good component of a healthy diet, contributing unsaturated fatty acids, fiber, protein, folate, minerals, antioxidants, and phytochemicals - Another great food source of healthy fats is fish, especially oily, cold-water fish such as anchovies, sardines, trout, albacore tuna, and salmon. The American Heart Association recommends at least two weekly servings of these fish, which provide omega-3 fatty acids, protein, vitamin D, and other key nutrients. Research shows that the oil found in these fatty fish—rich in healthy fats—lowers triglyceride levels, blood pressure, and heart rate, so it's not surprising that eating fish regularly is associated with a lower risk of CVD. Many companies sell fish oil as a dietary supplement, but it is questionable whether the general population's supplementation with omega-3 fish oil yields the same health benefits as consuming whole fish. However, the American Heart Associate does support the use of fish oil supplements for reducing the risk of future cardiovascular events in individuals with prior heart disease. Whereas whole fish consumption is encouraged, some types of fish can have high levels of mercury and other environmental pollutants. Thus, it is prudent to limit consumption of certain species, such as shark, swordfish, king mackerel, and tilefish.

Coconut Oil and Heart Health

We are currently seeing a fascination in the United States with coconut oil, a source of saturated fatty acids, as advertisements present it as a panacea of sorts. The purported benefits to heart health, however, are not supported by current scientific evidence. Several studies have found that it raises LDL cholesterol to the same degree as saturated fats from other sources, such as butter, beef fat, and palm oil. This is not particularly surprising as coconut oil contains more saturated fat than any other commonly consumed fat in the U.S. diet.

What clear patterns emerged in the Bogalusa study?

When all known risk factors were considered in the Bogalusa study, a clear pattern emerged: "We found that those individuals who had higher levels of known risk factors on the average had more fatty streaks—the precursors to plaques—in their coronary arteries and aortas than individuals who had lower levels," recalls William Newman, a pathologist with Louisiana State University School of Medicine in New Orleans, who performed autopsies for the Bogalusa study. In other words, although many of them were not even old enough to vote, these young people already had telltale signs of heart disease. Some even had developed full-blown plaques that were beginning to obstruct blood flow. Had these young people lived, those with the higher levels of atherosclerosis would have been at risk for a heart attack or other complications of heart disease.

myocardial infarction

When blood flow is blocked in the coronary artery, which supplies blood to the heart, people experience a heart attack, or myocardial infarction.

What are the effects of different unsaturated fats?

different unsaturated fats have different effects on the body as well. Omega-6 polyunsaturated fatty acids, for instance, appear to improve blood lipid profiles, especially when they take the place of saturated fatty acids, reducing the risk of heart disease. The American Heart Association suggests that this type of fat should make up no less than 5-10% of our total calories, given that they appear to reduce inflammation, a culprit in the initiation of plaque development.

Family History and CVD

individuals with a family history of heart disease at an early age are more likely to develop CVD, as are African Americans, and both men and women are at increased risk as they age. But there are many risk factors people of all ages can modify, most significantly through diet, exercise, and other lifestyle practices

What is the % of Americans who eat a poor diet for heart health?

more than 90% of Americans eat a "poor" diet for heart health, according to the American Heart Association.

Concentrations of Cholesterol and Heart Health (CVD)

the concentrations of cholesterol and triglycerides in blood are a major risk factor for CVD. Blood cholesterol levels measuring less than 200 milligrams of cholesterol per deciliter of blood (mg/dl)—the standard units of measurement for cholesterol—are considered desirable. Yet the average cholesterol level for a U.S. adult is just under 200 mg/dl—meaning the average American has a borderline high level. It is of even greater concern that approximately 40% of adults have cholesterol levels that exceed 200 mg/dl. People with high levels of total blood cholesterol have approximately twice the risk of heart disease as those who do not. Normal triglyceride levels vary by age and sex, but anything above 200 mg/dl is considered elevated. High triglyceride levels are common in people with heart disease or diabetes and correlate with lower levels of HDL cholesterol, or "good" cholesterol.