A key component to a healthy lifestyle is one’s diet. We are what we eat! Our bodies are literally made up of proteins, carbohydrates, and fats. You can think of the proteins as the building blocks and machinery of the body, while the carbohydrates supply the fuel for the machinery to run optimally. The fats are a diverse group; not only do they serve to insulate our body against the elements, but when needed they are utilized as a back-up energy reserve. Fats also play a crucial structural role, as they are the key components that make up the membranes surrounding each of the billions of cells in the human body.
Because of the many integral roles of fat in the body, it is important to consume the proper amount and types of fat. The primary types of dietary fats include monounsaturated, polyunsaturated, saturated, and trans fats.
Monounsaturated and Polyunsaturated Fats:
Both monounsaturated and polyunsaturated fats have been shown to lower your blood cholesterol levels when substituted for the saturated fats (and trans fats). Monounsaturated fats have been studied extensively for their protective role in lowering coronary heart disease (CHD) risk. Monounsaturated fat, the primary fat found in olive oil, is an important component of the heart-healthy Mediterranean diet. One reason for this health benefit is that monounsaturated fats have been shown to lower low-density lipoprotein (LDL) cholesterol (bad cholesterol) without lowering the high-density lipoprotein (HDL) cholesterol (good cholesterol) levels. A lower LDL:HDL ratio is known to reduce one’s risk for CHD.
Significant levels of polyunsaturated fats are found in canola, olive and peanut oils, and avocados. Foods high in polyunsaturated fats include safflower, sesame, sunflower, corn, and soy oils, and many nuts and seeds. The American Heart Association recommends limiting polyunsaturated fat intake to no more than 10 percent of total calories, with monounsaturated fats making up the rest of the total fat intake – up to 20 percent of total calories.
Saturated Fats:
Saturated fats are the primary dietary component responsible for raising LDL cholesterol levels. Saturated fats are typically found in animal products. Foods high in saturated fats include fatty meats, whole milk, cheeses, ice cream, and butter. An excellent way to reduce your saturated fat intake is to change from whole-milk products to either low-fat or nonfat products. Also, when preparing your meats trim all excess fat before cooking. Due to the increased CHD risk associated with dietary saturated fat levels, it is recommended to limit your saturated fat intake to no more than 7 percent of your total calories.
Trans Fats:
Recent research indicates that trans fats tend to raise LDL cholesterol levels, but not to the same degree as consuming saturated fats. Trans fats also lower HDL cholesterol when used instead of the naturally occurring oils such as olive or canola oil. This actually raises the LDL:HDL ratio, which can increase one’s risk for CHD – opposite of the effect seen with monounsaturated and polyunsaturated fats.
Hydrogenation is a process that turns liquid vegetables oils into the more solid margarines. Hydrogenation adds hydrogen atoms to a fat molecule. The more hydrogen atoms that are added the more hydrogenated and solid the fat becomes. Trans fats are a byproduct of the hydrogenation process. The more solid the margarine (as in stick margarines) the more trans fats it contains. Thus, soft tub margarines are best due to their lower trans fatty acid content.
Fortunately, the Nutrition Facts Panel currently lists the trans fat content of a food product. Also, make sure to read the ingredients label and choose foods that contain
unhydrogenated vegetable oils rather than hydrogenated oils. The
American Heart Association recommends limiting your trans fat intake as much as possible with the ultimate goal to consume less than 1 g of trans fats per day.
How Much Dietary Fat Should We Eat?
The
American Heart Association,
National Heart, Lung, and Blood Institute (NHLBI), and the
American Diabetes Association have recently released new dietary recommendations for dietary fat intake. These recommendations are based on the
Therapeutic Lifestyle Change (TLC) diet from the NHLBI’s, 2001
ATP III guidelines.
While the recommendations stress the importance of limiting one’s fat intake to no more than 25-35 percent of total calories, the major focus of the new recommendations is more on the “types” of fats than the ”amount” of total fat consumed. The recommendations stress replacing saturated and trans fats with the more heart-healthy monounsaturated and polyunsaturated fats (See table).
Nutrient Composition of the TLC Diet |
Nutrient |
Recommended Intake |
Saturated fat* |
<7% of total calories |
Polyunsaturated fat |
Up to 10% of total calories |
Monounsaturated fat |
Up to 20% total calories |
Total fat |
25%-35% of total calories |
Carbohydrate† |
50-60% of total calories |
Fiber |
20-30 g/d |
Protein |
Approximately 15% of total calories |
Cholesterol |
<200 mg/d |
Total calories‡ |
Balance energy intake and expenditure to maintain desirable body weight/prevent weight gain |
* Trans fatty acids are another LDL cholesterol-raising fat that should be kept at a low intake
† Carbohydrates should be derived predominantly from foods rich in complex carbohydrates including grains, especially whole grains, fruits, and vegetables
‡ Daily energy expenditure should include at least moderate physical activity (contributing ~200 kcal/d) |
Summary of the Therapeutic Lifestyle Change (TLC) diet based on NHLBI/NCEP ATP III guidelines.
Although these recommendations focus on the types of fat, it is still important to consume total dietary fat in moderation. Fat contains more than double the calories per gram than either carbohydrates or protein, so consuming excess fat can lead to an unwanted weight gain
- Fat = 9 calorie per gram
- Carbohydrate = 4 calorie per gram
- Protein = 4 calorie per gram
Following is an example of how to calculate the approximate grams of monounsaturated fat you would need in a day based on a 2,000 calorie diet:
Example: 2,000 calories x 15% = 300 calories. There are 9 calories in 1 gram of fat. 300 calories divided by 9 calories per gram of fat = 33 grams monounsaturated fat.
Information about the amount of total fat, monounsaturated fat, polyunsaturated fat, and
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trans fat in a food product can be found in a food product’s Nutrition Facts Panel.
Source: Michele M. Doucette, PhD
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