In this pyramid level are complex carbohydrates. Carbohydrates are
derived mainly from plants, including foods such as fruits, vegetables,
pasta, rice, legumes (beans), and other grains fall in this category.
Carbohydrates are very important to the body since they are the primary
source of energy. Some body tissues, such as red blood cells and most parts
of the brain, can only use carbohydrate (glucose) for energy. You should
eat 6-11 servings of carbohydrates each day, comprising 55-65% of your
Carbohydrates are broken down by the body into glucose, which i
form of sugar that is carried in the blood and transferred to cells for
energy. Some carbohydrates, such as pasta and bread, have been labeled
fattening. This, however, can be said of all foods, no matter their
nutritional makeup. When a person consumes too many calories, the excess
will be stored as body fat, whether the foods were carbohydrates, proteins,
Complex carbohydrates are long chains of glucose molecules. They are
usually comprised of starches, which is the product of carbohydrate storage
in plants. The major sssource of complex carbohydrates are whole grain
products, such as whole wheat bread, brown rice, pasta, and beans.
In fruits and vegetables are a lot of vitamins. The chemical
structures of the vitamins are all known, and all of them have been
synthesized; the vi
well-balanced diet usually satisfies the minimum vitamin requirements of
human beings. The Recommended Dietary Allowance (RDA) of each vitamin is
the standard guideline put forward by the Food and Nutrition Board,
National Academy of Sciences-National Research Council. It is based on the
nutritional needs of an average, healthy person. Different amounts may be
recommended for children, older people, lactating mothers, or people
dealing with an ongoing disease process.
Vitamins were originally classified according to their solubility in
water or fats, and as more and more were discovered they were also
classified alphabetically. The fat-soluble vitamins are A, D, E, and K; the
B complex and C vitamins are water soluble. A group of substances that
decrease blood capillary fragility, called the vitamin PPP group, are no
longer considered to be vitamins.
What does it do? Vitamin A is a fat-soluble vitamin with four major
functions in the body: (1) It helps cells reproduce normally—a process
called differentiation (cells that have not properly differentiated are
more likely to undergo pre-cancerous changes). (2) It is required for
vision; vitamin A maintains healthy cells in various structures of the eye
and is required for the transduction of light into nerve signals in the
retina. (3) It is required for normal growth and development of the embryo
organs in embryonic development. (4) It may be required for normal
reproductive function, with influences on the function and development of
sperm, ovaries and placenta.
What does it do? Vitamin C is a water-soluble vitamin that has a number of
biological functions. Acting as an antioxidant, one of vitamin C’s
important functions is to protect LDL cholesterol from oxidative damage.
(Only when LDL is damaged does cholesterol appear to lead to heart disease,
and vitamin C may be one of the most important antioxidant protectors of
LDL.) Vitamin C may also protect against heart disease by reducing the
stiffness of arteries and the tendency of platelets to clump together.
Vitamin C is needed to make collagen, the “glue” that strengthens many
parts of the body, such as muscles and blood vessels. Vitamin C also plays
important roles in wound healing and as a natural antihistamine. This
vitamin also aids in the formation of liver bile and helps to fight viruses
and to detoxify alcohol and other substances.
Vitamin E (tocopherol) occurs in at least seven molecular forms,
designated alpha-, beta-, gamma-, delta-, epsilon-, zeta-, and eta-
tocopherol; all exist as light yellow, viscous oils. The best source is
vegetable oils. Other sources include green leafy vegetables, wheat germ,
and eggs. Tocopherol is necessary for the maintenance of cell membranes. It
is a potent antioxidant ; numerous studies have pointed to a protective
effect against arterial plaque buildup and cancer. It is helpful in the
relief of intermittent claudication (calf pain) and in preventing problems
peculiar to premature infants. In large doses, it has an anticoagulant
In this level are a lot of calcium. Calcium is the mineral in your
body that makes up your bones and keeps them strong. Ninety-nine percent of
the calcium in your body is stored in your bones and teeth. The remaining
1% is in your blood and soft tissues and is essential for life and health.
Without this tiny 1% of calcium, your muscles wouldn’t contract correctly,
your blood wouldn’t clot and your nerves wouldn’t carry messages.
It is mainly the calcium in your diet that spares, or protects, the
calcium in your bones. In addition to their structural role, your bones are
your emergency supply of calcium. Your body actually tears down and builds
bone all of the time in order to make its calcium available for your body’s
functions. If you don’t get enough calcium from the food you eat, your body
automatically takes the calcium you need from your bones. If your body
continues to tear down more bone than it replaces over a period of years to
get calcium, your bones become weak and break easily. This leads to the
crippling bone disease called “osteoporosis.”
Protein molecule that consists of but a single polypeptide chain is
said to be monomeric; proteins made up of more than one polypeptide chain,
as many of the large ones are, are called oligomeric. Based upon chemical
composition, proteins are divided into two major classes: simple proteins,
which are composed of only amino acids, and conjugated proteins, which are
composed of amino acids and additional organic and inorganic groupings,
certain of which are called prosthetic groups . Conjugated proteins include
glycoproteins , which contain carbohydrates; lipoproteins, which contain
lipids; and nucleoproteins, which contain nucleic acids.
Classified by biological function, proteins include the enzymes,
which are responsible for catalyzing the thousands of chemical reactions of
the living cell; keratin, elastin, and collagen, which are important types
of structural, or support, proteins; hemoglobin and other gas transport
proteins; ovalbumin, casein, and other nutrient molecules; antibodies,
which are molecules of the immune system (see immunity ); protein hormones,
which regulate metabolism; and proteins that perform mechanical work, such
as actin and myosin, the contractile muscle proteins.
Fats and cholesterol have important functions in the body. Fats and
oils are also called lipids. Fats are the most concentrated source of food
energy. Per gram, fats have over twice as many calories as protein or
carbohydrates. Fats supply nine calories per gram, whereas carbohydrates
(sugars and starches) and protein supply four calories per gram. Our bodies
store excess dietary fats in fat cells to meet later energy needs. Excess
dietary carbohydrates and protein also are converted into fat by our bodies
and stored for later use.
In addition to supplying energy, fats have several important
functions. Fats give foods their characteristic flavors. Fats help provide
a feeling of satiety, or fullness. Dietary fats carry the fat-soluble
vitamins A, D, E, and K. Fats are also a source of the essential fatty
acids, linoleic acid and linolenic acid. Because the body cannot make these
essential fatty acids, they must be provided in the diet.
Cholesterol is often confused with fat. Cholesterol is not a
triglyceride, but a sterol. Sterols are fat-like compounds, made in the
body and found in foods. Cholesterol is part of the protective layer around
nerve fibers and is a building block for cell walls. Cholesterol is also
needed for the production of certain hormones, vitamin D, and bile.
Often fat and cholesterol are present together in food. However, the
fat content of a food does not necessarily parallel cholesterol content.
For example, vegetable oils that contain no cholesterol are still 100% fat.
Further, chicken and fish may contain less fat than some cuts of beef, but
the cholesterol content is similar. Cholesterol is present in muscle tissue
as well as fat.