What is fat and why do I need it...

Fat is a major source of energy for the body and it helps the absorption of fat-soluble vitamins and carotenoids. While fat in our diet is essential to our health, too much saturated fat is associated with obesity, high blood pressure, coronary heart disease, and colon cancer. General guidelines for using fat in our diet are presented below.

  • Our liver uses saturated fats to manufacture cholesterol. Excessive dietary intake of saturated fats raise blood cholesterol levels, especially low-density lipoproteins (LDLs). The recommended daily intake of saturated fats should be kept below 10% of total caloric intake.
  • Unlike the saturated fats, polyunsaturated fats (found in corn, soybean, safflower, and sunflower oils) may lower your total blood cholesterol level. However, large amounts of polyunsaturated fats also have a tendency to reduce your high-density lipoproteins (HDLs), so they should also be limited to 10% of total caloric intake.
  • Monounsaturated fatty acids are found mostly in vegetable and nut oils such as olive, peanut, and canola. These fats reduce blood levels of LDLs by a small amount without affecting HDLs; they should be limited to 10-15% of total caloric intake.
  • There are some indications that trans-fatty fatty acids raise LDL and lower HDL cholesterol levels.
  • Total calories from fat should not constitute more than 30% of your total daily calories.
  • Remember that 1g of fat produces 9 calories compared with 4 calories/gram of protein or carbohydrates.

For more information on fats, see Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids, 2002, Chapter 8, pp 335-432, Food and Nutrition Board (FNB), Institute of Medicine (IOM); and National Cholesterol Education Program (NCEP) ATPIII Guidelines, September 2002. Also see my Cholesterol, Carbohydrates, and Protein pages.

Fat deficiency signs?

  1. Dry scaly skin, dermatitis (indicates a possible linoleic acid deficiency)
  2. Hand tremors
  3. Inability to control blood pressure (may indicate a prostaglandin deficiency)

If you suspect you have a fat deficiency, contact your doctor or healthcare professional immediately.

What is fat?

A fatty acid is a long hydrocarbon atomic chain capped by a carboxyl group (COOH). Common fatty acids are: palmitic acid, stearic acid, oleic acid, and linoleic acid. Palmitic and stearic acid carbon atoms are always joined by hydrogen atoms, they are saturated with hydrogen atoms; oleic acid carbon atoms are joined by a carbon double bond and two hydrogen atoms are missing, they are monounsaturared; lineoleic acid carbon atoms are joined by multiple carbon double bonds, they are polyunsaturated.

To make a normal fat, three fatty acid atoms are bound together with glycerol to form a triglyceride. Triglycerides that contain palmitic acid and stearic acid (for example, butter) are known as saturated fats and are usually solid at room temperature. Triglycerides with monounsaturated (for example, olive oil and canola oil) or polyunsaturated fatty acids (for example, essential fatty acids) are usually liquid at room temperatures. To solidify liquid fat you have to hydrogenate it; that is, you have to saturate it with hydrogen by breaking the carbon double bonds and attach hydrogen atoms. A side effect of hydrogenation are trans-fatty acids.

Ingested fats enter the digestive system and are broken down into their glycerol and fatty acid components by the Lipase enzyme, these components are then reassembled into triglycerides for transport in the bloodstream.

Essential fatty acids

The most common fatty acids are found in animal fats and they can also be created directly from carbohydrates; they include:

  • Palmitic acid
  • Stearic acid
  • Oleic acid

Other fatty acids called essential fatty acids (EFA) can't be created by your body and must be ingested, they include:

  • Linoleic acid (LA) (omega-6)
  • Arachidonic acid (AA) (omega-6)
  • Gamma linolenic acid (GLA) (omega-6)
  • Dihomogamma linolenic acid (DGLA) (omega-6)
  • Alpha linolenic acid (LNA) (omega-3)
  • Eicosapentaenoic acid (EPA) (omega-3)
  • Docosahexaenoic acid (DHA) (omega-3)

Essential fatty acids fall into two groups: omega-3 and omega-6. The 3 and 6 refer to the first carbon double bond position on the fatty acid chain. All essential fatty acids are polyunsaturated, and the 3 and 6 mean that the first double bond is either 3 or 6 carbons in from the end. Food sources high in Omega-6 fatty acids include: corn oil, sunflower oil and soybean oil. High levels of Omega-3 fatty acids can be found in flax seeds, pumpkin seeds, walnuts, salmon, trout and tuna. Omega-3 and Omega-6 EFAs should be balanced in the diet at a ratio of 2-to-1, rather than the normal 20-to-1 ratio seen in most Western diets.

Updated: March 11, 2003