This is the continuation of last issue’s first installment on
food planning, talking in detail about the constituents of our diet.
Proteins are the basis of many animal body structures such as
muscles, skin, and hair. They also form the enzymes that control chemical
reactions throughout the body. Each molecule is composed of amino acids. The
body requires amino acids to produce new proteins and to replace damaged
Most meats such as chicken contain all the essential amino acids needed for
humans. As there is no protein or amino acid storage provision, amino acids must
be present in the diet. Excess amino acids are discarded, typically in the
urine. For all animals some amino acids are essential, signifying an animal
cannot produce them internally and some are non-essential. About twenty amino
acids are found in the human body, and about ten of these are essential and,
therefore, must be included in the diet.
A diet that contains adequate amounts of amino acids is particularly important
in some situations, such as during early development and maturation, pregnancy,
lactation, or injury (a burn, for instance).
A complete protein source contains all the essential amino acids; an incomplete
protein source lacks one or more of the essential amino acids. It is possible to
combine two incomplete protein sources (e.g. rice and beans) to make a complete
protein source and characteristic combinations are the basis of distinct
cultural cooking traditions. However, complementary sources of protein don’t
need to be eaten at the same meal to be used together by the body. Sources of
dietary protein include meats, tofu and other soy-products, eggs, legumes, and
dairy products such as milk and cheese.
Dietary minerals are the chemical elements required by living
organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen
that are present in nearly all organic molecules. Some are heavier than the four
just mentioned, including several metals, which often occur as ions in the body.
Most dietitians recommend that these be supplied from foods in which they occur
naturally or at least as complex compounds, or sometimes even from natural
inorganic sources (such as calcium carbonate from ground oyster shells). Some
minerals are absorbed much more readily in the ionic forms found in such
sources. On the other hand, minerals are often artificially added to the diet as
supplements; the most famous is likely iodine in iodized salt.
Many elements are essential in relative quantity; they are usually
called “bulk minerals”. Some are structural, but many play a role as
electrolytes. Elements with recommended dietary allowance (RDA) greater than
200 mg/day are, in alphabetical order :
· Calcium, a common electrolyte, but also needed structurally (for muscle and
digestive system health, bone strength, some forms neutralize acidity, may help
clear toxins, provides signaling ions for nerve and membrane functions).
· Magnesium builds bone, causes strong peristalsis, increases flexibility,
· Phosphorus, required component of bones; essential for energy processing.
· Potassium, a very common electrolyte (heart and nerve health).
· Sodium and Chlorine, both very common electrolytes are not generally found in
dietary supplements, despite being needed in large quantities, because the ions
are very common in food: typically as sodium chloride, or common salt. Excessive
sodium consumption can deplete calcium and magnesium, leading to high blood
pressure and osteoporosis.
· Sulfur, for three essential amino acids and therefore many proteins (skin,
hair, nails, liver, and pancreas). Sulfur is not consumed alone, but in the form
of sulfur-containing amino acids.
Many elements are required in trace amounts, usually because they
play a catalytic role in enzymes. Some trace mineral elements (RDA < 200 mg/day)
are, in alphabetical order:
· Cobalt required for biosynthesis of the vitamin B12 family of coenzymes.
Animals cannot biosynthesize B12, and must obtain this cobalt-containing vitamin
in the diet.
· Copper is required as a component of many redox enzymes, including cytochrome
· Chromium is required for sugar metabolism.
· Iodine is required not only for the biosynthesis of thyroxine, but probably,
for other important organs as breast, stomach, salivary glands, thymus etc.; for
this reason iodine is needed in larger quantities than others in this list, and
sometimes classified with the macro-minerals
· Iron is required for many enzymes, and for hemoglobin and some other proteins.
· Manganese is used for the processing of oxygen.
· Molybdenum is required for xanthine oxidase and related oxidases
· Nickel is present in urease.
· Selenium is required for peroxidase (antioxidant proteins).
· Zinc is required for several enzymes such as carboxypeptidase, liver alcohol
dehydrogenase, and carbonic anhydrase.
Next issue we will take a look at water, vitamins and phytochemicals.