Dietary Fats and Their Effects on Blood Cholesterol Levels, Part I
To Your Health -- CHRC Newsletter
Winter 2003
Here we are at the start of the New Year, a time when many people make resolutions. A popular resolution is to eat a healthier diet. To help you gain a better understanding of a healthy diet, we are talking about dietary fats in Part 1 with Karen Astrachan M.S., R.D., CDE, Supervisor of Nutrition Services at PAMF. Part 2 will focus on carbohydrates and fiber.
TYH: Everyone has a blood test for cholesterol at some point in their lives. What are the components of this blood test?
KA: Cholesterol travels in the blood in packages called lipoproteins. Just as water and oil do not mix, cholesterol, which is fatty, does not mix with blood, which is like water. So, in order to be able to travel in the bloodstream, the cholesterol combines with protein, making a lipoprotein. This lipoprotein carries cholesterol through the bloodstream.
These components make up a "lipid profile," which is the overall lab test for the following:
Each of these values indicates a lipoprotein level in your blood. Each lipoprotein has a specific relationship to your risk for heart disease.
Low Density Lipoprotein(LDL): A level of less than 130 milligrams per deciliter (mg/dl) is desirable.* This component is considered as "bad" cholesterol. LDL carries most of the cholesterol in the blood and is responsible for causing plaque build-up and blockage in the arteries. Thus, the higher your LDL level, the greater your risk for developing heart disease. If you already have diabetes or heart disease or are at high risk for developing them, it is important to keep your LDL level at or below 100 mg/dl.
High Density Lipoprotein (HDL): Optimal level is 60mg/dl or greater.* HDL is considered as "good" cholesterol since it transports the blood cholesterol to the liver, and thus leads to its removal from the body. In this way, HDL prevents cholesterol from building up in the arteries. If your HDL level is below 40mg/dl, you are at increased risk for heart disease. The higher your HDL level, the lower your risk for heart disease.
Triglycerides (TG): Optimal level is less than 150mg/dl.* This component is also considered as "bad" cholesterol. Most body fat is stored in fat tissues in the form of TG. Only a small portion of your TG is found in the bloodstream. If your TG level is elevated, in addition to altering your dietary fat intake, you may also need to modify your carbohydrate intake-more in Part 2.
TYH: Are there different types of dietary fats? How do they affect cholesterol level?
KA: Yes! Great question. Too often people lump all dietary fats into one category: BAD. However, not all fats are created equal.
Saturated fats are predominantly found in animal foods. They are one type of fat responsible for raising total blood cholesterol levels because they raise LDL cholesterol and triglyceride levels.
Foods high in saturated fats include whole fat dairy products like milk, yogurt, butter, cheese, ice cream; fatty meats, sausage, bacon, lard, and poultry skin.
Trans fats are like saturated fats. Trans fats also are responsible for raising total blood cholesterol levels by raising LDL cholesterol and triglyceride levels. In addition they lower HDL cholesterol levels. Remember, HDL is the good cholesterol, the one we want to be high, not low. Trans fats are found in foods such as margarine, vegetable shortening, fried foods, French fries, most commercial snack foods such as pastries, crackers, pies, cakes, cookies, soups, and frozen meals.
Polyunsaturated fats are predominantly found in plant foods and seafood. They reduce total blood cholesterol levels by decreasing LDL cholesterol and triglyceride levels. They consist of both omega-6 and omega-3 polyunsaturated fats. Omega-6 fatty acids, found in vegetable oils such as corn oil, sunflower oil, cottonseed oil, mayonnaise, sesame oil, and margarine, may negatively impact your HDL cholesterol level by lowering it. Omega-3 fatty acids, found in fatty cold-water fish such as salmon, mackerel, sardines, anchovies, herring, as well as in soybeans, tofu, English walnuts, and flaxseeds, may help to increase your HDL cholesterol level. Omega-3 fatty acids may also have other heart protective benefits.
Monounsaturated fats are predominantly found in plant foods. They reduce total blood cholesterol levels by lowering LDL cholesterol and triglyceride levels when they are used to replace saturated fats and carbohydrates. You may also see an increase in your HDL cholesterol level if you use monounsaturated fats in place of trans fats and/or omega-6 polyunsaturated fats. Sources of monounsaturated fats include olive oil, canola oil, peanut butter without additives, avocado, olives, tahini paste, and all types of nuts. Remember to check the label for hidden added fats such as hydrogenated oils.
TYH: Should we still be concerned about eggs and their
cholesterol content?
KA: Dietary cholesterol as in egg yolks-and incidentally, organ meats such as liver, kidney, gizzards, and brain-can raise your blood cholesterol level if consumed in excess. But remember that dietary fats (saturated and trans fats) are the primary culprit in today's society leading to worsening of the lipid profile and increasing the risk of heart disease. It is still a good idea to keep egg yolk consumption down to 3 per week if you do not have high cholesterol and 2 per week if you do have elevated cholesterol. The American Heart Association recommends keeping dietary cholesterol consumption down to less then 200 mg per day, about the equivalent amount in one egg yolk.
TYH: Trans fats have recently been in the news. Let's discuss this further.
KA: Although trans fats have received a lot of attention in the media in the past year they are not "new" fats. They occur naturally in small amounts in some meats and dairy products. But the majority of trans fats are found in processed foods. According to the US Department of Agriculture, 40% of all foods on grocery store shelves contain trans fats. Trans fats are in many products, even ones you would not suspect, and it's hard to avoid them altogether.
In the 1980s and 1990s, using trans fats in foods became popular as they were considered a healthy alternative to animal fats. So food manufacturers started using hydrogenation, a technique dating back to 1900s-heating liquid vegetable oil and partially hydrogenating it (by adding hydrogen ions), thus solidifying it into shortening and margarine. Partially hydrogenating oil makes it a trans fat.
Hydrogenation allows food to be stored on shelves for long periods of time without going rancid. The general belief was that switching from saturated fats to partially hydrogenated oils in processed foods was beneficial.
TYH: Are trans fats still considered a good substitute for saturated fats?
KA: No! Research in recent years tells a different story. Trans fats have now been found to be equally as harmful as, if not worse than, saturated fats found in animal foods. Like saturated fats, trans fats also raise the level of bad cholesterol (LDL) and triglycerides in your blood, which can increase your risk of heart attacks and strokes. But trans fats go one step further-they lower your blood levels of good cholesterol (HDL), the one that helps keep arteries clean.
In a study reported in the New England Journal of Medicine in
November 1997, based on the Nurses' Health Study of 80,000 women, researchers estimated that people could reduce their risk of heart disease by 53% if they replace 2% of calories from trans fats with unsaturated fats. And a replacement of only 5% of calories from saturated fat with unsaturated fat would lower the risk by 42%.
TYH: Are there any dietary guidelines for trans fats?
KA: Currently, there are no specific dietary guidelines for trans fats. The National Academy of Sciences recommends that you keep your daily intake of trans fats as low as possible. However, food labels do not have to list the amount of trans fats in the same way as they are required to list saturated fats-even though both fats promote heart disease.
The Food and Drug Administration (FDA) has proposed an amendment to its regulations on nutritional labeling that will require the mandatory declaration of the amount of trans fats in food to be listed separately on the "Nutrition Facts" label. The FDA hopes to publish the final ruling in early 2003. While it may be impossible to eliminate trans fats altogether, you can still make simple changes to decrease your consumption of them.
TYH: Until such regulation is enacted, how can we tell if a food product contains trans fats, and if so, how much?
KA: Currently the only way to tell if a product has trans fats is to read the list of ingredients for any type of partially hydrogenated, hydrogenated, or fractionated oil. All of these terms mean the food contains hidden trans fats.
If hydrogenated fat is listed near the top of the ingredient list, then the food may contain an undesirable amount of trans fat. Choose a healthier alternative! By cutting down on your consumption of processed foods and increasing your consumption of fruits, vegetables, and whole grain products, you can cut down your consumption of trans fats.
TYH: Are there any healthier alternatives to butter and margarine?
KA: Yes, there are margarines being produced without trans fats. Read the label to check for the presence of hydrogenated fats. Also available in your supermarket are margarines made from plant extracts that may help lower your cholesterol levels if used in place of butter or other trans fat-containing margarines. Two of these margarines are Benecol® and Take Control®. Another good alternative is using monounsaturated oil in cooking or avocado in a sandwich.
TYH: Can you consume too little fat in your diet?
KA: A certain amount of unsaturated fats is essential for our health. We need fat to perform many diverse physiological functions in our bodies. A good rule of thumb is to consume at least 10% of your calories from fat, primarily unsaturated fats. A diet too low in fat can cause scaly skin, hair loss, impaired wound healing, low energy, fatigue, menstrual irregularities, and fertility problems.
TYH: What are the current guidelines for intake of dietary fats?
KA: The American Heart Association and National Cholesterol Education Program recommend keeping total fat intake between 25-35% of calories, with saturated fat constituting less than 7% of your total caloric intake, polyunsaturated fats up to 10% of total caloric intake, and monounsaturated fats up to 20% of total caloric intake.
TYH: In summary, what would your recommendation be for a balanced diet?
KA: Reduce total fat by decreasing consumption of foods rich in saturated fats, trans fats, and cholesterol. Replace these fats with unsaturated fats, with emphasis on monounsaturated fats and omega-3 fatty acids. Choose fish more often. Additionally, limit intake of processed foods and foods high in added sugars; replace these foods with wholesome foods such as whole grains, fruits, vegetables and legumes. Also, exercise daily, control your weight, and manage your stress.
This article is the opinion of the author(s) and not necessarily that of your health care provider, the Palo Alto Medical Clinic, the Palo Alto Medical Foundation or Sutter Health. This information is provided for your general information and education only, and should not be relied upon for personal diagnosis or treatment. If you feel like you have an illness or need emotional support for a problem, please contact you personal physician NOW.
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