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. 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.

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 a 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. Fat is high in calories and small amounts can add up quickly. If you eat more calories than you need, you will gain weight. Excess weight is inked to poor health.

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 fat 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. Simply stated, fat is made up of varying amounts of fatty acids. It's the type and amount of fatty acid found in food that determines the effect of the fat on your health.

There are two main types of potentially harmful dietary fat — fat that is mostly saturated and fat that contains trans fat:

  • Saturated fat. This is a type of fat that comes mainly from animal sources of food, such as red meat, poultry and full-fat dairy products. 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.
  • Trans fat. This is a type of fat that occurs naturally in some foods in small amounts. But most trans fats are made from oils through a food processing method called partial hydrogenation. By partially hydrogenating oils, they become easier to cook with and less likely to spoil than do naturally occurring oils. Research studies show that these partially hydrogenated trans fats 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 that contain trans fat are solid at room temperature. Because of this, they're typically referred to as solid fats. They include beef fat, pork fat, butter, shortening and stick margarine.

The types of potentially helpful dietary fat are mostly unsaturated:

  • 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.
  • 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.
  • Omega-3 fatty acids. One type of polyunsaturated fat is made up of mainly omega-3 fatty acids and may be especially beneficial to your heart. Omega-3, found in some types of fatty fish, appears to decrease the risk of coronary artery disease. It may also protect against irregular heartbeats and help lower blood pressure levels. There are plant sources of omega-3 fatty acids. However, the body doesn't convert it and use it as well as omega-3 from fish.

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. Fish high in omega-3 fatty acids include salmon, tuna, trout, mackerel, sardines and herring. Plant sources of omega-3 fatty acids include flaxseed (ground), oils (canola, flaxseed, soybean), and nuts and other seeds (walnuts, butternuts and sunflower).

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.

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 Dietary Guidelines for Americans 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.

Type of fat Recommendation
Total fat This includes all types of dietary fat. Limit total fat intake to 20 to 35 percent of your daily calories. Based on a 2,000-calorie-a-day diet, this amounts to about 44 to 78 grams of total fat a day.
Monounsaturated fat While no specific amount is recommended, the guidelines recommend eating foods rich in this healthy fat while staying within your total fat allowance.
Polyunsaturated fat While no specific amount is recommended, the guidelines recommend eating foods rich in this healthy fat while staying within your total fat allowance.
Omega-3 fatty acids While no specific amount is recommended, the guidelines recommend eating foods rich in this healthy fat while staying within your total fat allowance.
Saturated fat Limit saturated fat to no more than 10 percent of your total calories. Limit to 7 percent to further reduce your risk of heart disease. Based on a 2,000-calorie-a-day diet, a 10 percent limit amounts to about 22 grams of saturated fat a day, while 7 percent is about 15 grams. Saturated fat intake counts toward your total daily allowance of fat.
Trans fat No specific amount is recommended, but the guidelines say the lower the better. Avoid trans fat by looking at food labels and by checking for the term "partially hydrogenated."
Cholesterol Less than 300 milligrams a day. Less than 200 milligrams a day if you're at high risk of cardiovascular disease.

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.

If watching fat content is a good strategy, is it even better to try to eliminate all fat from your diet? No. 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.

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:

  • Use the Nutrition Facts label when selecting foods. Read food labels and look for the amount of trans fat listed. By law a serving of food containing less than 0.5 grams of trans fat can be labeled as 0 grams. Therefore, it is important to also check ingredient lists for the term "partially hydrogenated." It's best to avoid foods that contain trans fat and those that have been partially hydrogenated.
  • Prepare fish, such as salmon and mackerel, instead of meat at least twice a week to get a source of healthy omega-3 fatty acids. Limit sizes to 4 ounces of cooked seafood a serving, and bake or broil seafood instead of frying.
  • Use liquid vegetable oil instead of solid fats. For example, saute with olive oil instead of butter, and use canola oil when baking.
  • Use olive oil in salad dressings and marinades.
  • Use egg substitutes instead of whole eggs when possible.
  • Select milk and dairy products that are low in fat.
Feb. 11, 2014