Encyclopedia of Health and Medicine

192 Nutrition and Diet
configurations. Unsaturated fats, in moderation,
appear to help lower blood cholesterol levels.
Polyunsaturated fats include safflower, corn, and
sunflower oils. Monounsaturated fats, which
many health experts believe offer the greatest
health benefits among the fatty acids, include
olive, canola, and peanut oils as well as olives,
avocados, almonds, pecans, cashews, and peanuts.
Many “vegetable oil” products blend oils from different
sources.
Trans fatty acids, or trans fats, are processed fats
that contain extra hydrogen atoms to make them
more solid at room temperature and more resistant
to oxidative degradation than the base fatty
acids are in their natural forms. Sometimes called
hydrogenated fats, trans fats raise blood cholesterol
levels higher and faster than do saturated
fats. The most common dietary sources of trans
fats are margarines, shortening, and partially
hydrogenated cooking oils. Processed baked goods,
snack foods, fried foods, and fast foods are common
dietary sources of trans fats.
OMEGA-3 FATTY ACIDS AND HEALTH RISK REDUCTION
Research suggests that tipping the balance to
favor consumption of omega-3 fatty acids can
significantly lower the risk for HEART disease and
cancer (especially PROSTATE CANCER and BREAST
CANCER) in some people. Eicosapentaenoic acid
(EPA) and docosahexaenoic acid (DHA) are two
omega-3 fatty acids found in high concentrations
in mackerel, salmon, lake trout, herring, sardines,
and anchovies. The American Heart Association
recommends two servings weekly of any
of these fish.
The body requires fatty acids for numerous
functions beyond energy, including HORMONE synthesis
and cell membrane integrity. Nearly all fatty
acids, in foods and in the body, take the form of
triglycerides. The essential fatty acids are linoleic
acid and linolenic acid, from which the body can
synthesize other fatty acids. Linoleic acid is an
omega-6 fatty acid; its primary dietary sources are
meats, dairy products, and vegetable oils.
Linolenic acid is an omega-3 fatty acid; soybeans,
flaxseed and soybean oils, nuts, and seeds are its
primary dietary sources. The body requires these
fatty acids in relative balance. EATING HABITS that
disproportionately deliver linoleic acid (saturated
fats such as in meats) appear to correlate with
increased risk for CVD (notably HYPERTENSION) and
some types of cancer (notably hormone induced).
Proteins Dietary proteins, also called peptides,
are chains of amino acids; amino acids are chemical
structures (molecules) of carbon, hydrogen, oxygen,
and nitrogen. Of the hundreds of amino acids
in the body, 20 combine in various forms to create
the majority of the body’s proteins. Nine are essential,
meaning they must enter the body from outside
sources such as foods. Using these nine amino
acids and other substances within the body, the
body synthesizes all the other amino acids it needs
and combines the amino acids to create proteins.
Proteins are key messenger substances in the body.
DNA (deoxyribonucleic acid), the GENETIC CODE each
nucleated cell contains, is a protein strand. Other
proteins carry its instructions to molecules
throughout the body, giving the directions for the
amino acid sequences that are the foundation of
the body’s structure and function.
Dietary proteins are also chains of amino acids
and are complete or incomplete, according to
whether the protein chain contains all nine essential
amino acids (complete) or not (incomplete).
Animal-based foods (meats, poultry, fish, and
dairy) and soybeans provide complete dietary proteins.
Plant-based foods provide incomplete proteins,
though combining consumption of different
plant-based foods can deliver a combination of
proteins that are complete. Dietary variety is the
most effective way to ensure the body receives
adequate amounts of all the essential amino acids.
AMINO ACIDS
Essential Amino Acids Nonessential Amino Acids
histidine isoleucine alanine argine
leucine lysine asparagine aspartic acid
methionine phenylalanine cysteine glutamic acid
threonine tryptophan glutamine glycine
valine proline serine
taurine tyrosine
After consumption dietary proteins undergo
digestion and metabolism, processes that break
them down to their amino acid structures. The
body then reassembles the amino acids into structures
it requires for its functions. The body even-