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Fats and Cholesterol - The Good, The Bad, and The Healthy Diet
Unfortunately, this simple message now seems largely out of date. Detailed research--particularly that done at Harvard--shows that the total amount of fat in the diet, whether high or low, has no real link with disease. Rather, what really matters is the type of fat in the diet. There are bad fats that increase the risk for certain diseases and good fats that lower the risk. The key is to substitute good fats for bad fats. And cholesterol in food? While it's true that dietary cholesterol is linked to heart disease, it certainly isn't the food villain that it's been portrayed as. What is of most concern is blood cholesterol--the cholesterol circulating in your blood. High blood cholesterol levels greatly increase the risk for heart disease. But surprisingly, the amount of cholesterol in food is not very strongly linked to cholesterol levels in the blood. The biggest influence on blood cholesterol levels is the mix of fats in the diet. The Cholesterol - Heart Disease Connection Cholesterol is a wax-like substance. The liver makes it and links it to carrier proteins called lipoproteins that let it dissolve in blood and be transported to all parts of the body. Why? Cholesterol play essential roles in the formation of cell membranes, some hormones, and Vitamin D. Too much cholesterol in the blood, though, can lead to problems. In the 1960s and 70s, scientists established a link between high blood cholesterol levels and heart disease. Deposits of cholesterol can build up inside arteries. These deposits, called plaque, can narrow an artery enough to slow or block blood flow. This narrowing process, called atherosclerosis, commonly occurs in arteries that nourish the heart (the coronary arteries). When one or more sections of heart muscle fail to get the blood, and thus the oxygen and nutrients, they need, the result may be the chest pain known as angina. In addition, plaque can rupture, causing blood clots that may lead to heart attack, stroke, or sudden death. Fortunately, the buildup of cholesterol can be slowed, stopped, and possibly even reversed. Cholesterol-carrying lipoproteins play a central role the development of atherosclerotic plaque and cardiovascular disease. The two main types basically work in opposite directions. Low-density lipoproteins (LDL) carry cholesterol from the liver to the rest of the body. When there is too much LDL cholesterol in the blood, it can be deposited on the walls of the coronary arteries. Because of this, LDL cholesterol is often referred to as the "bad" cholesterol. High-density lipoproteins (HDL) carry cholesterol from the blood back to the liver, which processes the cholesterol for elimination from the body. HDL makes it less likely that excess cholesterol in the blood will be deposited in the coronary arteries, which is why HDL cholesterol is often referred to as the "good" cholesterol. When you have your cholesterol checked, the results will indicate your total blood cholesterol level. If you fasted overnight before giving a blood sample, the test results should also include separate counts for your HDL and LDL. In general, the higher your LDL and the lower your HDL, the greater your risk for atherosclerosis and heart disease. For adults age 20 years or over, the most recent federal guidelines - from the National Cholesterol Education Program - recommend the following target levels: Dietary Fat, Dietary Cholesterol, and Blood Cholesterol Levels One of the most important determinants of blood cholesterol level is fat in the diet--not total fat, as mentioned already, but the specific types of fat. Research has shown that some types of fat are clearly good for blood cholesterol and others, clearly bad. As for cholesterol in food, it does affect blood cholesterol levels, but not nearly as much as many people believe. For some people with high cholesterol, reducing the amount of cholesterol in the diet has a small but helpful impact on blood cholesterol levels. For others, the amount of cholesterol eaten has little impact on the amount of cholesterol circulating in the blood. Dietary Cholesterol and Eggs While it is well known that high blood cholesterol levels are associated with an increased risk for heart disease, scientific studies have shown that there is only a weak relationship between the amount of cholesterol a person consumes and their blood cholesterol levels or risk for heart disease. In a study of over 80,000 female nurses, Harvard researchers actually found that increasing cholesterol intake by 200 mg for every 1000 calories in the diet (about an egg a day) did not appreciably increase the risk for heart disease. Eggs Long vilified by well-meaning doctors and scientists for their high cholesterol content, eggs are now making a bit of a comeback. Recent research by Harvard investigators has shown that moderate egg consumption--up to one a day--does not increase heart disease risk in healthy individuals. While it's true that egg yolks have a lot of cholesterol--and, therefore may slightly affect blood cholesterol levels--eggs also contain nutrients that may help lower the risk for heart disease, including protein, vitamins B12 and D, riboflavin, and folate. So, when eaten in moderation, eggs can be part of a healthy diet. People with diabetes, though, should probably limit themselves to no more than two or three eggs a week, as the Nurses' Health Study found that for such individuals, an egg a day might increase the risk for heart disease. Similarly, people who have difficulty controlling their blood cholesterol may also want to be cautious about eating egg yolks and choose foods made with egg whites instead. Dietary Fats The Bad Fats Some fats are bad because they tend to worsen blood cholesterol levels. Saturated Fats Saturated fats are mainly animal fats. They are found in meat, seafood, whole-milk dairy products (cheese, milk, and ice cream), poultry skin, and egg yolks. Some plant foods are also high in saturated fats, including coconut and coconut oil, palm oil, and palm kernel oil. While saturated fats raise total blood cholesterol levels more than dietary cholesterol does, they tend to raise both the "good" HDL and the "bad" LDL cholesterol. Trans Fats Trans fatty acids are fats produced by heating liquid vegetable oils in the presence of hydrogen. This process is known as hydrogenation. The more hydrogenated an oil is, the harder it will be at room temperature. For example, a spreadable tub margarine is less hydrogenated and so has fewer trans fats than a stick margarine. Most of the trans fats in the American diet are found in commercially prepared baked goods, margarines, snack foods, and processed foods. Commercially prepared fried foods, like French fries and onion rings, also contain a good deal of trans fat. Trans fats are worse for cholesterol levels than saturated fats because they not only raise LDL (bad) cholesterol, but also lower HDL (good) cholesterol. The Good Fats Some fats are good because they can improve blood cholesterol levels. Unsaturated Fats--Polyunsaturated and Monounsaturated Unsaturated fats are found in products derived from plant sources, such as vegetable oils, nuts, and seeds. There are two main categories: polyunsaturated fats (which are found in high concentrations in sunflower, corn, and soybean oils) and monounsaturated fats (which are found in high concentrations in canola, peanut, and olive oils). In studies in which polyunsaturated and monounsaturated fats were eaten in place of carbohydrates, these good fats decreased LDL levels and increased HDL levels. For more great nutritional and health information, start your Self-size weight loss program today! |
