Most vegetables and fruits consumed as such contain only small
amounts of fat. Saturated Fats
Often solid at room temperature, saturated fats are high in well-
marbled meats and whole-
milk dairy products.
High amounts of saturated fat are found in beef, pork, lamb,
chicken skin, butter, whole milk, and cheese.
Some vegetable fats are also saturated; for example, palm kernel
and coconut oils. Polyunsaturated Fats
Vegetable oils are the principal sources of linoleic and alpha-
linolenic acids. Arachidonic acid is found in small amounts in lard, which also contains about 10% of linoleic acid. Fish oils contain large quantities of a variety of longer chain fatty acids having three or more double bonds including eicosapentaenoic and docosahexaenoic acids. Trans (Hydrogenated) Fats
A small amount of
trans
fat is found naturally in animal-based
foods. Most
trans
fat is a specific type of fat formed when liquid oils
are made into solid fats like s
hortening and hard margarine.
Food manufacturers solidify unsaturated liquid fats through a
process called hydrogenation. This is used to create margarine or shortening for use in deep-fat frying or as an ingredient in baked goods, snack foods, crackers, and candy. Hydrogenation increases the shelf life and flavor stability
of foods containing these fats.
The FDA estimates the average adult US daily intake of
trans
fat
is 5.8 grams or 2.6% of calories.
On average, Americans consume 4 to 5 times as much saturated
fat as
trans
fat in their diet.
Heart-Healthy Fat
For more information about saturated, unsaturated, and
trans
fats, see
Heart-Healthy Fat
on page
87
.
Function, General
Dietary fat is a major source of energy. Fat provides about two-
thirds of the energy muscles require. It provides the most concentrated source of energy of any foodstuff, 9 calories per gram.
Fat is required for the absorption of fat-soluble vitamins
(vitamins A, D, E, and K) and carotenoids.
As a food ingredient, fat provides taste, consistency, and stability
and helps us feel full.
Fat is important for proper
growth, development, and
maintenance of good health.
Fat maintains healthy skin and ha
ir, cushions the bones and vital
organs, and protects the body from cold temperature. Energy
More than 80% of alpha-linolenic acid and much linoleic acid
are consumed in energy production.
Essential Fatty Acids
By definition, essential fatty acids cannot be synthesized in the
body and are required for health.
The main biological roles of essential fatty acids are as
regulators of gene expression; as structural components of cell membranes, particularly in nerve tissue and in the retina; and as precursors of eicosanoids. Linoleic Acid
Linoleic acid is essential as a precursor of arachidonic acid, a
substance required for the production of eicosanoids. Read more about eicosanoids on the next page.
Nutrition for Sports, Essentials of 79