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. 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:

  • 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.
  • 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:

  • 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. 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.

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References
  1. Dietary Guidelines for Americans, 2010. U.S. Department of Health and Human Services. http://www.cnpp.usda.gov/DGAs2010-PolicyDocument.htm. Accessed Jan. 31, 2011.
  2. Gillman MH, et al. Dietary fat. http://www.uptodate.com/home/index.html. Accessed Jan. 21, 2011.
  3. American Heart Association scientific position: Fat. American Heart Association. http://www.americanheart.org/presenter.jhtml?identifier=4582. Accessed Feb. 11, 2011.
  4. Van Horn L, et al. The evidence for dietary prevention and treatment of cardiovascular disease. Journal of the American Dietetic Association. 2008;108:287.
  5. Duyff RL. American Dietetic Association Complete Food and Nutrition Guide. 3rd edition. Hoboken, N.J.: John Wiley & Sons; 2006.
  6. Zeratsky KA (expert opinion). Mayo Clinic, Rochester, Minn. Feb. 4, 2011.
  7. Hensrud DD (expert opinion). Mayo Clinic, Rochester, Minn. Jan. 31, 2011.
  8. Paniagua J, et al. A MUFA-rich diet improves postprandial glucose, lipid and GLP-1 responses in insulin-resistant subjects. Journal of the American College of Nutrition. 2007;26:434.
  9. Nelson JK (expert opinion). Mayo Clinic, Rochester, Minn. Feb. 4, 2011.
NU00262 Feb. 15, 2011

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