Why should I eat fat? How much is too much? Does fat from food make me fat? Why do they tell me I should eat olive oil, but I should avoid French fries? These are all common questions, and the facts can be hard to keep straight. Not all fat in food is detrimental to your health. In fact, fat is a necessary component to a healthy diet, and essential to well being. There are differences in dietary fat, and here’s some information to help you get the facts straight. Certain sources of fat should be avoided or limited in the diet, but not all fat is equal.
Dietary fat serves multiple functions. First of all, dietary fat is a source of energy to help fuel the body and also ensures its growth and development. All fat contributes 9 calories per gram, independent of what type of fat it is. Calories can be thought of as energy or fuel for the body. Although each type of fat is calorically the same, they each affect the body differently once digested. Not only that, but fat is a nutrient that helps the body absorb essential vitamins called “fat soluble vitamins” which are needed by the body. When fat is digested in the body, it triggers hormones that signal feelings of fullness or “satiety” and eventually tell the brain to stop eating. Just like the nutrients protein and carbohydrate, fat contributes calories, and one well-known characteristic of dietary fat is that it provides flavor to food.
Fats are classified into different types: monounsaturated fat, polyunsaturated fat, saturated fat, cholesterol, and trans fat. Monounsaturated and polyunsaturated fats are known as “good” fat because they lower harmful cholesterol in the body known as LDL (low density lipoprotein) cholesterol or bad cholesterol. The good cholesterol known as HDL (high density lipoprotein) cholesterol is generally what you want to raise because it is protective of the heart.
Monounsaturated fat is the most desirable form of dietary fat because it lowers the body’s total cholesterol and LDL levels, while sparing the HDL level, which is healthy for the heart. Polyunsaturated fat is also desirable, but while it lowers total and LDL cholesterol levels, it can also lower the HDL level. Good sources of polyunsaturated fat include: margarine, salad dressings, mayonnaise, oils (corn, soybean, safflower, sunflower, cottonseed), and seeds (pumpkin, sunflower). Good sources of monounsaturated fat include: olive oil, canola oil, nuts and nut butters, olives, and avocados. As moderation is important to keep in mind, no more than 10% of your total calories should come from polyunsaturated fat (20 grams on an 1800 calorie/day diet), and no more than 20% should come from monounsaturated fat (40 grams on an 1800 calorie/day diet).
Saturated fat should be limited in the diet because it can raise LDL cholesterol levels and also increase risk for heart attack and stroke. The difference in the chemical structure of saturated fat is what causes it to act differently in the body than mono and poly unsaturated fats. Sources of saturated fat include: whole fat dairy products, cheese, butter, lard, fatty cuts of meat, poultry with skin on it, palm oil, coconut oil, sweets and desserts, egg yolks, fast foods, snack foods and fried foods made with hydrogenated and partially hydrogenated oils. Saturated fat should be limited to less than 7% of total calories (or 14 grams on an 1800 calorie/day diet).
Trans fat should be avoided as much as possible in the diet. These fats are formed from hydrogenated oils, which are made industrially to help stabilize products. The process of hydrogenation turns liquid fat, like oil, into a solid fat. Not only does trans fat raise LDL cholesterol and increase risk for heart disease, it also lowers HDL cholesterol. Although the amount of trans fats in the food supply has decreased, some remain in hydrogenated and partially hydrogenated vegetable oils, stick margarines, snack foods, and prepared desserts. The Dietary Guidelines do not provide a recommendation for trans fat because individuals should consume as little as possible.
Dietary cholesterol is found in food sources that come from animals such as meat, poultry, and dairy. The body also makes cholesterol for physiological and structural functions, which is why individuals do not need to consume more than 300 mg/day. Limiting cholesterol intake to less than 200 mg/day can further decrease risk for cardiovascular disease.
According to the 2010 Dietary Guidelines for Americans, a healthy adult should consume between 20 – 35% of daily calories from dietary fat. A well balanced diet includes healthy food sources of fat such as: fish (salmon, herring, mackerel, tuna, trout); lean skinless turkey or chicken; unsalted nuts and seeds; liquid oils (canola, safflower and olive oil); low-fat or fat-free milk and milk products.
As a general guideline, saturated and trans fats are usually solid at room temperature and are referred to as “solid” fats. Unsaturated fats are usually liquid at room temperature and are referred to as “oils.” All food can be part of a healthy meal plan but understanding how different nutrients affect the body can improve your choices and help you to make smart ones. For more information, talk with a Registered Dietitian to find out what fits best into your daily preferences.
©Adrienne Hatch, MS, RD, LD/N
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