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
- 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.
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,
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
Cholesterol Education Program (NCEP) ATPIII Guidelines, September
2002. Also see my Cholesterol, Carbohydrates,
and Protein pages.
- Dry scaly skin, dermatitis
(indicates a possible linoleic acid deficiency)
- Hand tremors
- 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,
- Linoleic acid (LA) (omega-6)
- Arachidonic acid (AA) (omega-6)
- Gamma linolenic acid (GLA)
- Dihomogamma linolenic acid
- Alpha linolenic acid (LNA)
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
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.