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The Necessity of Minerals in a Healthy Diet
Much attention is given to the necessities of vitamins
for good health, but the role of minerals is as important. Even if one
mineral is lacking the body can not function properly.
Minerals are divided into two groups - macro elements and trace
elements. They combine with vitamins, form enzymes and are necessary for
almost every physiological process. Minerals are found in a broad range
of plant and animal foods, as well as in drinking water.
It is not always apparent what the function of minerals are and year by
year new minerals are being included in the list of essentials. Like
vitamins the best way to overcome this problem is by including a very
wide range of foods in your diet.
Calcium
Calcium is the most abundant mineral in the body. The RDA for adults is
1200 milligrams.
About 99% is found in the bones and teeth. Calcium also has a role to
play in the regulation of various body functions including the
cardiovascular and nervous systems. It keeps your heart beating
regularly, alleviates insomnia and helps to metabolize iron.
The best natural sources are sea vegetables Wakame: 1300, Arame: 1170,
Kelp: 1093, (Mg per 100g). Taken from Vegetables from the Sea by Teruko
& Seibin Arasaki] , low-fat yogurt, skim milk, beans, tofu, sesame
seeds, nuts, sardines with bones, salmon and green vegetables.
Calcium absorption is hindered by the presence of oxalate s in the food.
Calcium absorbability of kale (a low-oxalate vegetable) was compared
with that of milk in 11 normal women. Absorption of calcium was
excellent in all subjects. In 9 of the 11 women, kale calcium
absorbability was higher than that of milk calcium.
For optimal calcium absorption, a proper amount of vitamin D is needed
each day. This can be obtained from fortified milk and cereals, or 15
minutes to an hour of midday sunshine.
It appears there is a threshold of calcium intake, below which skeletal
reserves may be used to meet daily calcium needs. Studies show that loss
of estro prompts rapid loss of bone mineral, especially from the spine,
regardless of calcium intake.
Intakes over 2000 milligrams per day may lead to hypercalcemia, induce
constipation, and inhibit the intestinal absorption of iron, zinc, and
other essential minerals.
Chromium
It is difficult to estimate the chromium requirement, but a range of 50
micrograms to 200 micrograms per day is tentatively recommended.
Trivalent chromium is required for maintaining normal glucose
metabolism. Evidence shows that chromium improves glucose tolerance [Riales,
R., & Albrink, M. J., American J. Clin. Nutr., Vol. 34, pg 2670] .
Diabetes and coronary heart disease are associated with low chromium
concentrations in human tissue.
The chemical forms of chromium in foods are not known with certainty,
but the bioavailability of chromium compounds has been found to be high
in brewer's yeast, shell fish, whole wheat bread and mushrooms.
An increased incidence of bronchial cancer has been associated with
exposure to dusts containing chromate. But the carcinogenicity of
certain chromates bears no relevance to the nutritional role of non
toxic trivalent chromium.
Copper
Because of the uncertainty of quantitive human requirements, it is not
possible to establish an RDA. 1.5 milligrams to 3.0 milligrams per day
has been recommended as a safe and adequate range of dietary copper
intake for adults.
Copper is an essential nutrient, necessary for extensive body functions.
It converts iron to hemoglobin , is essential for the utilization of
vitamin C and stops the degeneration of the nervous system. In a study
of 10 men who got less than half the suggested copper intake for 6
weeks, four of them responded with a significant increase in
cholesterol. [Journal American Dietetic Association, July 1990. Pg 96.
response to low-copper diet ... according to researchers with USDA's
Agricultural Research Service]
The best natural sources are shell fish, sea vegetables, nuts, seeds,
beans and peas. It is found abundantly in tap water because of
contamination from copper pipes.
Toxicity from dietary sources is extremely rare, but supplementation
should be avoided as an excess can lower zinc levels, produce insomnia,
hair loss and depression.
Iodine
Approximately 1 mcg per kilogram of body weight is required. The RDA for
adults is 150 micrograms.
Iodine is an essential component of the thyroid hormones thyroxine and
triiodothyronine. It is almost entirely used by the thyroid gland. The
thyroid gland controls metabolism, proper growth, helps burn up excess
fat and gives you more energy.
Deficiency of dietary iodine may result in decreased synthesis of the
iodine-containing thyroid hormones. This can lead to cretinism and
mental retardation. Iodine intake consistently lower than 50 mcg per day
usually leads to thyroid hypertrophy (ie. endemic goiter). In addition,
epidemiological and experimental studies suggest that endemic goiter
predisposes to cancer of the thyroid.
The best natural sources are seafoods and sea vegetables (kelp, arame
and kombu). Iodized salt is a regular source, providing about 75 mcg per
gram.
Individuals who are sensitive to iodine may react to excessive exposure
with iododerma, fever, salivary gland enlargement, visual problems
and/or other symptoms. Death from severe forms of iododerma has been
reported. Acute responses to the ingestion or injection of large doses
of an iodine-containing solution include cardiovascular collapse,
convulsions, and asthma attacks.
Adverse effects of iodine have also been reported from dietary
supplements, including seaweed extracts, vitamin and mineral
preparations. Goiter caused by high iodine intakes has been registered
in Japan. [Nagataski, S. 1974. Effect of excess quantities of iodine.
Pg. 329-344 in Handbook of Physiology, III, Endocrinology.]
The response to excess iodine is variable. Some individuals tolerate
large intakes without side effects, whereas others may respond adversely
to levels close to recommended intakes. Those who are most likely to
respond adversely are those living in endemic goiter areas or for other
reasons have habitually had a low intake of iodine, and those who are
sensitive to iodine.
The maximum tolerable level of iodine appears to range from 200 mcg per
day to 1000 mcg per day. These levels of intake are possible from diets
that include milk, iodized salt, seaweed and products containing the red
food coloring erythrosine which has high levels of iodine.
Generally, iodine intakes by the majority of the population in the USA
is considered safe and adequate.
Iron
Iron is a constituent of hemoglobin. Body iron content is regulated by
the amount absorbed. The absorption is influenced by body stores and by
the amount and type of iron in ingested foods. The RDA for adults is 15
milligrams.
It is a vital component of many enzymes, it can promote resistance to
disease and prevent fatigue. A trend toward reduced risk of melanoma was
observed by Stryker et al when iron intake was increased (not including
supplements).
A deficiency can cause anemia, resulting in impaired concentration,
reduced physical performance and work capacity, and decrease immune
function. Ascorbic acid is necessary for the proper assimilation of
iron.
The best natural sources of iron are sea vegetables, clams, cockles,
mussels, oysters, yeast, molasses, beans, nuts, seeds and cereals.
Tea, coffee, bran and phytates decrease iron absorption.
There are no reported cases of toxicity from foods but iron poisoning
may occur from ingesting large amounts of medicinal iron supplements.
Magnesium
Magnesium is known as the antistress mineral. The RDA for adults is 350
milligrams.
Many biochemical and physiological processes require magnesium. It is
necessary for vitamin C and calcium metabolism. It keeps teeth healthy,
brings relief from indigestion and can aid in fighting depression. More
than 300 enzymes are known to be activated by magnesium. It controls
cellular metabolism and maintains electrical potentials of nerve and
muscle membranes for the transmission of impulses across junctions.
The best natural sources are whole seeds, nuts, legumes, unmilled
grains, green vegetables and bananas.
Phytate or fiber may reduce magnesium absorption. Alcohol acts as a
diuretic, causing vast quantities to be lost in the urine.
There is no evidence that large dietary intakes of magnesium are harmful
to people with normal renal function. In cases of impaired renal
function and use of magnesium-containing drugs hypermagnesemia may
occur. Symptoms include nausea, vomiting and hypotension. As conditions
worsen respiratory depression, coma and asystolic arrest may occur.
Manganese
Because of the lack of manganese deficiency in adults, the current
dietary intakes satisfy the needs for this mineral. A provisional daily
dietary intake of 5.0 milligrams is recommended.
It is necessary for the use of biotin, B1 and C, by the body. It can
help eliminate fatigue, improve memory, reduce nervous irritability and
assure the proper digestion and utilization of food. A deficiency can
cause poor reproductive performance, growth retardation, abnormal
formation of bone and cartilage, and an impaired glucose tolerance.
The best natural sources are whole grains, cereal products, nuts and
green leafy vegetables. Dairy products, meat, fish, and poultry are poor
sources.
Toxicity has only been observed with workers exposed to high
concentrations of manganese dust or fumes in the air.
Nickel
Nickel is now quite firmly established as an essential nutrient, but no
Recommended Dietary Allowance (RDA) or Estimated Safe and Adequate
Intake (ESADI) has yet been set for nickel. [Root, E.J. Current
Perspectives on Nickel, Nutrition Today, Vol 25:3, June 1990.]
Research showed that nickel was to be found in blood and tissues at
quite consistent levels, that it is associated with DNA and RNA in
amounts that suggest physiological significance, and that it occurs also
in blood in amounts which appear biologically meaningful.
Nickel is required for normal growth and reproduction in animals, and
presumably in human beings as well. It appears to have a role in the
modulation of the immune system and in development of the brain. Since
brain is depleted in deficiency more than other tissues, the brain and
immune system should receive attention in future studies of nickel
deficiency.
The best sources of nickel include oatmeal, legumes, nuts, cocoa, whole
wheat bread, and some leafy vegetables such as kale and lettuce.
The danger of nickel toxicity from food appears to be very low, since
large amounts of nickel are required to produce any toxic effects
through ingestion. But in susceptible people, contact with nickel or
nickel salts cause skin irritations.
Chronic exposure at lower levels can cause cancer. Workers exposed to
nickel compounds have a higher than normal incidence of cancer of the
respiratory tract, particularly of the nasal cavities and lungs. Nickel
released from burning tobacco isthought to be responsible for at least
part of the carcinogenicity of tobacco smoke. There is no indication of
cancer arising from ingestion of the nickel in food.
Phosphorus
The precise requirement for phosphorus is unknown, but a 1 to 1 ratio of
calcium to phosphorus will provide sufficient phosphorus for most age
groups. The RDA for adults is 1200 milligrams.
Phosphorus is an essential component of bone mineral and is necessary
for normal bone and tooth structure. It is involved in almost all
physiological chemical reactions. It aids in growth and can lessen the
pain of arthritis.
The best natural sources are cereal grains, nuts, seeds, meat, poultry
and fish.
Aluminum hydroxide binds phosphorus, making it unavailable for
absorption. An excess of iron and magnesium have the same effect.
Phosphorus deficiency results in bone loss and is characterized by
weakness, anorexia and pain.
Potassium
Potassium is the principal intercellular cation. There is no RDA but a
minimum requirement of 1600 milligrams per day would be adequate.
Potassium is of great physiological importance, contributing to the
transmission of nerve impulses, the control of skeletal muscle
contractility, and the maintenance of normal blood pressure. Deficiency
symptoms include weakness, anorexia, nausea, drowsiness and irrational
behavior.
Potassium is found in most foods since it is an essential constituent of
all living cells. The richest dietary sources are unprocessed beans,
nuts, leafy green vegetables and fruit.
Low blood sugar levels (hypoglycemia), alcohol or smoking cause
potassium loss.
Acute intoxication (hyperkalemia) can cause cardiac arrest and prove
fatal.
Selenium
The RDA is 70 micrograms for male adults, 55 micrograms for females.
Selenium plays a role in pancreatic function, in hepatic heme
metabolism, and in the immune response. It has a close metabolic
interrelationship with the antioxidant vitamin E. Deficiency only occurs
simultaneously with a deficiency of vitamin E and can be cured by
supplementation of either. It can neutralize certain carcinogens so
possibly provide protection from some cancers.
The best natural sources of selenium are seafoods, eggs and depending on
the selenium content of the soils in which they are grown, grains and
seeds.
Sodium
Sodium is the principal cation of extracellular fluid. As the rate of
sodium loss can vary under different conditions there is no official
RDA, but the minimum daily requirement for healthy adults is 500
milligrams.
Sodium is crucial for regulating the membrane potential of cells and is
involved in active transport across cell membranes, it is pumped out in
exchange for potassium. It helps the nerves and muscles function
properly.
Sodium is found in abundance in most processed foods thus there is very
little chance of a deficiency occurring with the average Western Diet.
The best natural sources are salt, shellfish, anchovy, lox, spirulina,
wakame, cheese and red or green peppers.
The body may be depleted of sodium under extreme conditions of sweating
or chronic diarrhea.
Excessive intake of sodium can result in edema and hypertension.
Sulfur
Sulfur is used to treat many kinds of skin disorders. Sulfur cream,
lotion, ointment, and bar soap are used to treat acne. Sulfur ointment
is used to treat seborrheic dermatitis and scabies. Sulfur may also be
used for other conditions as determined by your doctor.
Zinc
The RDA is 15 milligrams per day for men and 12 milligrams per day for
women. Recent research suggests that men have a higher need for zinc
than do women. Thus, it is appropriate that the RDA is sex-specific for
zinc.
Zinc is an essential trace element that must be supplied in the diet of
human beings so that growth and health can be maintained. It is
necessary for protein synthesis and the metabolism of vitamin A, it
helps the healing process of internal and external wounds, decreases
cholesterol deposits and promotes mental awareness. A deficiency can
cause loss of appetite, growth retardation and immunological
abnormalities.
The best natural sources are oysters, nuts, wheatgerm, whole grain
products, brewers yeast, meat, eggs, legumes and seeds.
Zinc is more easily absorbed in small amounts than large amounts. Human
studies have shown that milk apparently inhibits zinc absorption.
Because cow's milk and milk products are the major sources of calcium
and higher levels of calcium have been recommended in women to protect
against bone loss, this could be a matter for concern. Its
bioavailability is reduced by protein or fiber.
Ingestion of zinc supplements exceeding 15 mg per day is not
recommended. Toxicity can cause gastrointestinal irritation and
vomiting.
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