Dietary Fats: Know Which Types to Choose

When choosing fats, pick unsaturated fat over saturated or trans fat. Here's how to know the difference.

By Mayo Clinic staff

Most foods contain several different kinds of fat, and some are better for your health than others are. You don't need to completely eliminate all fat from your diet. In fact, some fats actually help promote good health. But it's wise to choose the healthier types of dietary fat, and then enjoy them — in moderation.

The facts about dietary fat

There are numerous types of fat. Your body makes its own fat from taking in excess calories. Some fats are found in foods from plants and animals and are known as dietary fat. Dietary fat is one of the three macronutrients, along with protein and carbohydrates, that provide energy for your body. Fat is essential to your health because it supports a number of your body's functions. Some vitamins, for instance, must have fat to dissolve and nourish your body.

But there is a dark side to fat. The concern with some types of dietary fat (and their cousin cholesterol) is that they are thought to play a role in cardiovascular disease and type 2 diabetes. Dietary fat also may have a role in other diseases, including obesity and cancer.

Research about the possible harms and benefits of dietary fats (sometimes called fatty acids) is always evolving. And a growing body of research suggests that when it comes to dietary fat, you should focus on eating healthy fats and avoiding unhealthy fats.

Harmful dietary fat

The two main types of potentially harmful dietary fat:

1. Saturated fat. This is a type of fat that comes mainly from animal sources of food. Saturated fat raises total blood cholesterol levels and low-density lipoprotein (LDL) cholesterol levels, which can increase your risk of cardiovascular disease. Saturated fat may also increase your risk of type 2 diabetes.
2. Trans fat. This is a type of fat that occurs naturally in some foods, especially foods from animals. But most trans fats are made during food processing through partial hydrogenation of unsaturated fats. This process creates fats that are easier to cook with and less likely to spoil than are naturally occurring oils. These trans fats are called industrial or synthetic trans fats. Research studies show that synthetic trans fat can increase unhealthy LDL cholesterol and lower healthy high-density lipoprotein (HDL) cholesterol. This can increase your risk of cardiovascular disease.

Most fats that have a high percentage of saturated fat or trans fat are solid at room temperature. Because of this, they're typically referred to as solid fats. They include beef fat, pork fat, shortening, stick margarine and butter.

Healthier dietary fat

The two main types of potentially helpful dietary fat:

1. Monounsaturated fat. This is a type of fat found in a variety of foods and oils. Studies show that eating foods rich in monounsaturated fats (MUFAs) improves blood cholesterol levels, which can decrease your risk of heart disease. Research also shows that MUFAs may benefit insulin levels and blood sugar control, which can be especially helpful if you have type 2 diabetes.
2. Polyunsaturated fat. This is a type of fat found mostly in plant-based foods and oils. Evidence shows that eating foods rich in polyunsaturated fats (PUFAs) improves blood cholesterol levels, which can decrease your risk of heart disease. PUFAs may also help decrease the risk of type 2 diabetes. One type of polyunsaturated fat, omega-3 fatty acids, may be especially beneficial to your heart. Omega-3s, found in some types of fatty fish, appear to decrease the risk of coronary artery disease. They may also protect against irregular heartbeats and help lower blood pressure levels.

Foods made up mostly of monounsaturated and polyunsaturated fats are liquid at room temperature, such as olive oil, safflower oil, peanut oil and corn oil.

A word about cholesterol

Cholesterol isn't a fat. Rather, it's a waxy, fat-like substance. Your body manufactures some cholesterol. Your body also absorbs some dietary cholesterol — cholesterol that's found in foods of animal origins, such as meat and eggs. Cholesterol is vital because, among other important functions, it helps build your body's cells and produces certain hormones. But your body makes enough cholesterol to meet its needs — you don't need any dietary cholesterol.

Excessive cholesterol in your diet can increase your unhealthy LDL cholesterol level, although not as much as saturated fat does. This can increase your risk of heart disease and stroke. Most foods that contain saturated fat also contain cholesterol. So cutting back on these foods will help decrease both saturated fat and cholesterol. The exception to this is tropical oils, which are high in saturated fat but contain no cholesterol.

Recommendations for fat intake

Because some dietary fats are potentially helpful and others potentially harmful to your health, it pays to know which ones you're eating and whether you're meeting national recommendations. The 2010 Dietary Guidelines for Americans, issued by the Department of Agriculture, offer recommendations about dietary fat intake.

Here's a look at the recommendations and common sources of each type of dietary fat. Be aware that many foods contain different kinds of fat and varying levels of each type. For example, butter contains unsaturated fats, but a large percentage of the total fat is saturated fat. And canola oil has a high percentage of monounsaturated fat but also contains smaller amounts of polyunsaturated and saturated fat.

Source: Dietary Guidelines for Americans, 2010

Need help calculating what your daily fat intake should be in grams? Multiply your daily total calorie intake by the recommended percentage of fat intake. Divide that total by 9, which is the number of calories in a gram of fat. For example, here's how a 7 percent saturated fat limit looks if you eat 2,000 calories a day. Multiply 2,000 by 0.07 to get 140 calories. Divide 140 by 9 to get about 15 grams of saturated fat.

What about very low-fat diets?

If watching fat content is a good strategy, is it even better to try to eliminate all fat from your diet? Not necessarily. First, your body needs some fat — the healthy fats — to function normally. If you try to avoid all fat, you risk getting insufficient amounts of fat-soluble vitamins and essential fatty acids. Also, in attempting to remove fat from your diet, you may wind up eating too many processed foods touted as low-fat or fat-free rather than healthier and naturally lower fat foods, such as fruits, vegetables, legumes and whole grains. Instead of doing away with fat in your diet, enjoy healthy fats in moderation.

Tips for choosing the best types of dietary fat

So now that you know which types of dietary fat are healthy or unhealthy, and how much to include, how do you adjust your diet to meet dietary guidelines?

First, focus on reducing foods high in saturated fat, trans fat and cholesterol. Then emphasize food choices that include plenty of monounsaturated fats (MUFAs) and polyunsaturated fats (PUFAs). But a word of caution — don't go overboard even on healthy fats. All fats, including the healthy ones, are high in calories. So consume MUFA-rich and PUFA-rich foods instead of other fatty foods, not in addition to them.

Here are some tips to help you make over the fat in your diet:

• Read food labels and ingredient lists and avoid products with partially hydrogenated vegetable oil listed among the first ingredients.
• Saute with olive oil instead of butter.
• Use olive oil in salad dressings and marinades. Use canola oil when baking.
• Use egg substitutes instead of whole eggs when possible.
• Sprinkle slivered nuts or sunflower seeds on salads instead of bacon bits.
• Snack on a small handful of nuts rather than potato chips or processed crackers. Unsalted peanuts, walnuts, almonds and pistachios are good choices.
• Try nonhydrogenated peanut butter or other nonhydrogenated nut-butter spreads. Spread them on celery, bananas or whole-grain toast.
• Add slices of avocado, rather than cheese, to your sandwich.
• Prepare fish such as salmon and mackerel instead of meat twice a week. Limit sizes to 4 ounces of cooked seafood per serving.