The Basics of Human Nutrition
Taken as a whole, all of the elements and materials
that we eat or drink, and which our bodies require for good health,
are referred to as our Nutritional Requirements. These requirements
have only been studied and become fully known in this century: the Recommended
Dietary Allowances and the United States Recommended Daily Allowances.
The Recommended Dietary Allowances (RDA’s) have
been defined by the Food and Nutrition Board of the National Academy
of Sciences. They are the recommended daily intake of every known nutritional
requirement, broken down by age, weight, and sex. The Cambridge formulas
meet 100% of the RDA’s and the USRDA’s.
The United States Recommended Daily Allowances (USRDA’s)
have been specified by the Food and Drug Administration (FDA) to create
standards for use in food labeling. USRDA’s have been specified
for protein, most vitamins, and selected minerals. In most instances,
the USRDA’s represent the highest RDA suggested for any age, weight,
or sex group for each nutrient.
The Major Nutritional Elements
Nutritional elements can be broken down into major
categories. They are Macronutrients, Micronutrients, Dietary Fiber,
and Water. Let’s take a closer look at each one of these categories.
Macronutrients refer to the major nutrients,
which are required by the body in large quantities: Protein, Carbohydrate,
and Fat. Macronutrients are all calorie-containing nutrients, while
vitamins and minerals (micronutrients) contain no calories.
Protein is required to build and repair body
tissue. Each gram of protein contains 4 calories. Protein is made
up of amino acids. Of the 22 amino acids that comprise the various protein
structures in the body, nine are classified as essential (must be supplied
from foods); the remainders are non-essential (can be synthesized by
the body). The Cambridge formulas contain all the essential amino acids.
|Essential Amino Acids
||Non-essential amino acids
Carbohydrates are the principal dietary source of energy, being readily
metabolized, and with very little being stored in the body. Each gram
of carbohydrate contains 4 calories. Carbohydrates are classified
in three basic groups:
Monosaccharide - Simple sugars (glucose,
fructose, and galactose) that are quickly absorbed and used as fuel
by the body.
Disaccharide - More complex carbohydrates
(sucrose, maltose, and lactose), which must be broken down before they
can be used as, fuel by the body.
Polysaccharide - Very complex carbohydrates
(starch and cellulose) that require relatively long periods of time
to be broken down before they can be used as fuel by the body.
Fats are concentrated sources of energy, which are digested
more slowly and stored, in the fat tissues of the body, our main energy
reserve. Each gram of fat contains 9 calories. A small amount
of fat is essential in the diet to provide transport for fat-soluble
vitamins, structural support for tissue, and to maintain body temperature.
Dietary fat also serves as a source of essential fatty acids. There
are two kinds of fats: saturated fats and unsaturated fats.
Saturated fats are solid at room
temperature and are generally derived from animal and dairy sources,
such as butter or the fat in meat. The exceptions are coconut and palm
Unsaturated fats, as a general rule,
are liquid at room temperature, such as most vegetable oils.
Diets high in saturated fat are often associated with
elevated blood cholesterol levels and coronary heart disease. Their
partial replacement by diets containing unsaturated fats is often recommended.
Micronutrients are nutrients required by the body in
smaller amounts and include vitamins, minerals, and electrolytes. Although
the quantities required are small, the function of each is very important.
Vitamins are organic substances derived from
plants and animals and are needed daily in small amounts (milligrams
or micrograms) to maintain health and/or promote growth. None provide
energy; however, some facilitate the release of energy from protein,
carbohydrates, and fats. All are essential nutrients, which must be
provided by the diet.
There are 13 recognized vitamins and they fall into
two categories: fat soluble vitamins and water-soluble vitamins.
Fat Soluble Vitamins (A, D, E and K) are
absorbed through the intestinal membranes into the body proper with
the aid of fats in the diet or bile produced by the liver. They can
reach toxic levels if consumed in excessive quantities because they
are stored in the fat tissues of the body.
The main roles of these vitamins are as follows:
Vitamin A assists in the formation and maintenance
of healthy skin, hair, and mucous membranes; aids in the ability to
see in dim light (night vision); and is needed for proper bone growth,
tooth development, and reproduction. The U.S.RDA for Vitamin A is 5000
Vitamin D aids in the formation and
maintenance of bones and teeth and assists in the absorption and use
of calcium and phosphorus. The U.S.RDA for Vitamin D is 400 IU.
Vitamin E aids in the formation of
red blood cells, muscles, and other tissues and protects Vitamin A and
essential fatty acids from oxidations. The U.S.RDA for Vitamin E is
Vitamin K aids in the synthesis of
substances needed for the blood to clot and helps maintain normal bone
metabolism. Vitamin K is naturally synthesized in the human body from
other nutrients. There is no U.S.RDA for Vitamin K.
Water Soluble Vitamins (B-complex and C)
These vitamins do not require fat or bile to be absorbed and, for the
most part, are not stored in the body. Water-soluble vitamins must be
replenished frequently since they are used by the body or excreted.
Because they are soluble in water, these vitamins are more easily lost
in food storage, processing, or preparation (such as prolonged washing
Thiamine (B1) helps release energy
from carbohydrates and aids in the synthesis of an important nervous
system chemical. The U.S.RDA for Thiamine is 1.5 mg.
Riboflavin (B2) helps release energy
from carbohydrates, proteins, and fats and aids in facilitating energy
production in cells. The U.S.RDA for Riboflavin is 1.7 mg.
Vitamin B6 aids in the absorption
and metabolism of proteins, helps the body use fats, and assists in
the formation of red blood cells. The U.S.RDA for Vitamin B6 is 2 mg.
Folic Acid acts with vitamin B12
in synthesizing genetic material and aids in the formation of hemoglobin
in red blood cells. The U.S.RDA for Folic Acid is 400 mcg.
Pantothenic Acid helps in the metabolism
of carbohydrates, proteins, and fats and aids in the formation of hormones
and nerve regulating substances. The U.S.RDA for Pantothenic Acid is
Biotin aids in the formation of fatty
acids and helps release energy from carbohydrates. The U.S.RDA for Biotin
is 300 mcg.
Vitamin C aids in the formation of
collagen; helps maintain capillaries, bones, and teeth; helps protect
other vitamins from oxidation; and, may block formation of cancer causing
nitrosamine. The U.S.RDA for Vitamin C is 60 mg.
Because vitamins are chemical
compounds, sophisticated chemical and biological techniques allows technology
to isolate them and synthesize most of them; the body recognizes the
chemical structure and does not differentiate between natural and synthetic
sources in assimilation and metabolism.
Anti-Oxidant Vitamins such as Vitamin C, Vitamin E, and Beta Carotene (the chemical parent of Vitamin
A) are vitamins having anti-oxidant properties. Anti-oxidant vitamins
taken in amounts higher than the Recommended Daily allowances have been
shown to diminish the negative effect of free radicals. Free radicals
are molecules with an unpaired electron that roam through the body stealing
electrons from other healthy molecules. They are naturally present in
the body but their numbers are dramatically increased by stress or trauma
of almost any kind (including dieting). Free radicals wreak havoc by
damaging DNA, altering biochemical compounds, corroding cell membranes
and by killing cells out-right. Many researchers are convinced that
the cumulative effect of free radicals underlies the gradual deterioration
that is the hallmark of aging.
Anti-oxidant nutrients are made up of molecules with an extra electron.
When they encounter free radicals in the body, the free radical takes
the extra electron and is neutralized. Once a free radical has paired
its electron, it can do no damage to healthy cells thus reducing the
health risk, and, some think, retard the aging process. Opinions differ
as to the required amounts of anti-oxidants necessary to have a significant
effect. However, it seems clear that effective and safe levels fall
into the following ranges:
Vitamin C 200 mg to 2, 000 mg
Vitamin E 100 IU to 500 IU
Beta Carotene 10,000 IU to 25,000 IU
Minerals are inorganic elements, which have
a variety of essential functions in body compounds and reactions, such
as nerve and muscle function, bone and tooth formation. There are three
general classes of minerals; Macro Minerals, Trace Minerals and Electrolytes.
Macro Minerals are required in amounts of
100 mgs or more per day. They are Calcium, Phosphorus, and Magnesium.
Calcium is necessary for the formation of the body’s
skeletal system in early life. Calcium is also required for efficient
blood clotting and the proper function of nerve and muscles. Calcium
in the adult body is found in the skeleton in combination with Phosphorus
as the main structural material. However, the small amount of Calcium
that is found in the soft tissues and in body fluids, such as blood,
is of critical importance. The U.S.RDA for Calcium is 1000 mg.
Phosphorus is of vital importance
in energy metabolism. For the most part, Phosphorus is found in bones
in combination with Calcium. The calcium Phosphate present in bones
and teeth is an important structural material. About 10% of the Phosphorus
is found in the nervous system and in other soft tissues. The U.S.RDA
for Phosphorus is 1000 mg.
Magnesium interacts with over 200
enzymes in the body and is essential to all biosynthetic processes and
transmission of genetic codes. It is primarily found in the soft tissue
and skeletal structures. The U.S.RDA for magnesium is 400 mg.
Trace Minerals are Iron, Copper,
Zinc, Iodine, Fluoride, Chromium, Selenium, Manganese, and Molybdenum.
They are required in smaller quantities and each has a specific function
in the body.
Iron is an essential component of
hemoglobin, which transports oxygen in the blood from the lungs to cells
where oxygen is needed for energy metabolism. Iron also forms part of
myoglobin, a pigment which transports oxygen within muscle cells, and
the cytochrome system, which is involved in energy release processes
within all cells. The U.S.RDA for Iron is 18 mg.
Copper forms part of many enzyme
systems. Its metabolism in the body is closely related to that of iron.
The U.S.RDA for Copper is 2 mg.
Zinc plays a vital role in metabolism
as well as cell growth and repair. It is also important in maintaining
the function of the immune system. Bioavailability in natural food sources
varies widely. Seafood (especially oysters), eggs, and red meats are
the best natural sources of Zinc. Because the body does not store Zinc
for future use, it is important to insure that a regular supply is provided
in the diet. The U.S.RDA for Zinc is 15 mg.
Iodine is required for the synthesis
of thyroid hormones, which regulate many body functions. The U.S.RDA
for Iodine is 150 mcg.
Fluoride is important for bone strength
and provides resistance of tooth enamel. It is usually provided through
drinking water or tooth care products. There is No U.S.RDA for Fluoride.
The RDA is 50 mcg to 150 mcg.
Chromium is required for maintaining
normal glucose metabolism and acts as a cofactor for insulin. Chromium
is important for maintaining lean body tissue, can increase the metabolism
of fat and is thought to have an appetite suppressing effect. There
is no U.S.RDA for Chromium. The RDA for Chromium is 50 mcg to 200 mcg.
Selenium forms part of an essential
system that guards against damage to cell membranes and interacts with
Vitamin E. There is no U.S.RDA for Selenium. The RDS for Selenium is
50 mcg to 75 mcg.
Manganese functions in several enzyme
systems involved in protein and energy metabolism, the central nervous
system, and in normal bone structure. There is no U.S.RDA for Manganese.
The RDA for Manganese is 2 mg to 5 mg.
Molybdenum forms a vital part of
several enzyme systems within the cells of the body. The effect of inadequate
intakes of this trace element has not been described or demonstrated
because it is difficult to produce a diet with low enough content of
Molybdenum. Molybdenum may help prevent dental cavities. There is no
U.S.RDA for Molybdenum. The RDA for Molybdenum is 75 mcg to 250 mcg.
Note: As with some vitamins, certain minerals may
be toxic if taken in excessive amounts.
Electrolytes are Sodium,
Potassium, and Chloride. They are required in a balanced relationship
to maintain the acid base content of the body.
Sodium is important in maintaining
the correct distribution of water between the inside of the cells and
the fluids surrounding them. Sodium deficiency is usually associated
with dehydration due to excessive sweating in hot environments, heavy
exercise, or fever. In such circumstances, the volume of fluids outside
the cells is reduced and the blood volume is low. Sodium is widely distributed
in the body in fluids outside cells. The U.S.RDA for Sodium has not
Potassium is essential for the proper
functioning of the nervous system and the maintenance of acid base balance
in body fluids. It is found inside the muscle cells where it is essential
for their correct functioning. The U.S.RDA for Potassium hasn’t
Chloride is important for maintenance
of fluid and electrolyte balance; many chemical reactions within the
body are dependent on the correct acid base balance. The U.S.RDA for
Chloride has not been established.
All fiber comes from the cell walls of plants, which give plants their
firm structure, and from non-structured substances that are mixed with
plain starches. There are many different kinds of fiber and each has
Dietary fiber is generally defined
as the sum of carbohydrates and carbohydrate-like components of foods,
such as cellulose, lignin, hemicellulose, pentosan, gums, and pectin.
These non-digestible substances provide bulk in our diet and aid elimination.
The most common sources of dietary fiber are obtained
from whole grains, fruits, and vegetables. Fiber is not considered an
essential nutrient, but can be especially beneficial in weight loss.
The more fiber your diet contains, the few calories you’re likely
to consume, because fiber takes more time to chew, which slows the eating
process and allows time for the brain to receive the signal of being
Each of the Original Cambridge Diet and the Cambridge
Diet Food For Life formulas contain dietary fiber, which is important
to the body’s digestion and elimination process. Specific fiber
content varies within the different products.
While water is not a nutrient in the strictest sense, it is very important
and is often overlooked in discussions of nutrition. While we can survive
many days without food, we cannot exist for more than a few days without
water. Water makes up about 60% of our body weight; provides the main
transport systems (blood, lymph and digestion) for carrying nutrients
and oxygen to cells; carries electrolytes to regulate acid base balance;
regulates body temperature; is essential to digestion and absorption
of food; and aids in removing waste products. While water requirements
vary with levels of activity, as a general rule eight or more eight-ounce
glasses per day are recommended.
Common Nutritional Terms You May Encounter
Cholesterol - is a component of fat, which is derived
from animal fats and is also synthesized in the body. An excess of cholesterol
accumulated in the blood can be deposited on the walls of the arteries,
often causing clogging.
Energy Balance - Energy balance refers
to the point at which the number of calories consumed on a daily basis
is equal to the number of calories burned as fuel by the body on a daily
basis. The point at which energy balance is reached (measured in calories)
varies with metabolic rates, people require differing quantities of
food to perform the same functions. While each individual will have
a different energy balance point, for most people the balance point
will be between 1,500 and 3,000 calories per day.
Ketosis - Ketosis occurs when carbohydrates
are not readily available as an energy source and the body is breaking
down fat to meet its energy needs. When in ketosis, ketone bodies are
produced in the blood. When the body is not able to excrete the ketone
bodies through the urine rapidly enough, they concentrate in the blood,
producing ketosis. Mild ketosis such as that produced while on a very-low-calorie
diet produces a chemical state in the body that reduces hunger levels,
making it easier to stay on the diet.
Lactose Intolerance - Some people
have difficulty digesting the carbohydrate in milk (lactose). Before
lactose can be absorbed through the intestinal tract, it must first
be broken down into its component sugars (glucose and galactose) by
an intestinal enzyme called lactase. In almost all humans, lactase levels
are high at birth and for the first two years. After that, lactase levels
begin to drop with age, and in some people, nearly disappear.
Lactose intolerance results when people are unable
to digest most or all of the lactose. It can cause a variety of digestive
problems including excessive intestinal gas and diarrhea, when milk
products are consumed.
Lactose is present in The Original Cambridge Diet
formula; however, all Cambridge Food For Life products have been specially
produced with low lactose content.
Protein Efficiency Rating - The Protein
Efficiency Rating or PER, is a method for determining protein quality
and amino acid content. The FDA standard for protein quality is a PER
of 2.5 for food labeling purposes. All Cambridge shakes, soups, cereals,
and bar contain protein with a PER of 2.5 or higher.
Very Low Calorie Diet - Very
low calorie diet or “VLCD” is a term used to describe any
diet providing fewer than 800 calories per day.