Iodine constitutes about 0.00004% of the total human body
weight. It is found in highest concentration in the thyroid gland, muscles, and
various endocrine tissues. The primary function of iodine in the body is as a
constituent of the hormones thyroxin and triiodotyrosine, both of which are
secreted by the thyroid gland and affect growth, development, and the metabolic
rate of the body.
Iodine, as a constituent of thyroxin, plays an important
role in the efficient conversion of beta-carotene to vitamin A, with a
subsequent increase in the efficacy of protein synthesis and cholesterol
Iodine deficiency is the primary cause of simple goiter
and has been linked conclusively to cretinism.
Iodine is readily absorbed (almost 100%) from foodstuffs
and is excreted in the urine.
Iodine, upon absorption in the bloodstream, is
concentrated within the thyroid gland by an active transport system called the
"iodine pump." In the thyroid, iodine is oxidized to iodide by the enzyme
iodine peroxidase. In this form, iodine is incorporated into tyrosine residues
of the protein thyroglobulin proteins, whereupon it forms the active hormones
thyroxin and triiodotyrosine.
Low thyroxin and triiodotyrosine levels in the body are
"sensed" by the hypothalamus gland and stimulate the release of thyrotropin
releasing hormone (TRH) from the hypothalamus. TRH stimulates the anterior
pituitary to secrete thyroid stimulating hormone (TSH), which provokes
processes that synthesize and release thyroxin and triiodotyrosine from the
thyroglobulin protein. High thyroxin and triiodotyrosine levels provoke
decrease TRH production, which slows the production of thyroxin and
Thyroxin and triiodotyrosine enter the tissue cells of
the body by passive diffusion. Increase adenosine triphosphate (ATP)
consumption provokes an increased oxygen consumption and more expedient
metabolism of glucose, lipids, and amino acids. The body then has an overall
rise in basal metabolic rate.
High levels of thyroxin and triiodotyrosine can provoke
an increase in the number and size of mitochondrial cells, with a possible
inhibition of oxidative phosphorylation. This may result in an overall increase
in body heat.
Goitrogens, natural inhibitors of the thyroid gland, can
promote the development of goiter, a disorder characterized by an enlargement
of the thyroid gland in the neck region. Goitrogens are found in cabbage,
turnips, grape seeds, mustard, peanuts, cauliflower, and soybeans, as well as
other food sources. Cooking is an adequate way of inactivating these
Iodine has been used in the temporary
treatment of hyperthyroidism (Graves disease). Hyperthyroidism is a
disorder in which the thyroid is overactive, resulting in increased protein
metabolism, calcium imbalance, glucose intolerance, and overall increased
metabolism. Serum cholesterol and triglyceride levels are depressed, and the
patient may complain of perspiration and heat intolerance. Iodine
supplementation increases storage of the thyroid hormone thyroxine, helping to
prevent its release.
Iodine supplements can be used for the
prevention and cure of simple goiter, a disorder resulting from a deficiency in
dietary iodine intake.
Insufficient iodine intake can, and quite frequently
does, result in goiter. This condition is characterized by the swelling of the
thyroid gland in the neck region. This swelling is a result of an increased
proliferation of thyroid epithelial cells in order to compensate for low levels
of thyroid hormones in the body. Symptoms of goiter include compression of the
trachea (resulting in a hoarsening of the voice), chronic coughing, difficulty
in swallowing, and facial congestion.
Severe iodine deficiencies in pregnant women can result
in cretinism in the offspring, a disorder in which the child suffers from
stunted growth or dwarfism, swollen facial features, and varying degrees of
Adults suffering from a surgically damaged thyroid may
develop myxedema, a disorder with symptoms much resembling cretinism. These
symptoms include lowered body temperature and pulse rate, lethargy, retardation
of metabolic and mental processes, and a puffing of skin and tissues.
Excess dietary iodine is on the rise, and has many
nutritionists concerned. These rises are attributed to: iodine in iodized salt
found in many foods - especially prepackaged and fast foods; iodine in food
supplements when the supplement taker takes double or triple doses thinking
that if a little is good - more is even better (dangerous in this case); iodine
added as a disinfectant to drinking water; iodine supplements given to
livestock; iodine compounds used as dairy sanitizers; iodine used as a dough
conditioner in bakeries. Amount over 500% of the RDA are considered to be
dangerous and leads to a significant increase in the above outlined
Excessive intake of iodine may result in a condition
known as "iodine goiter." This type of goiter is characterized by an
enlargement of the thyroid gland and might be erroneously diagnosed as goiter
resulting from insufficient iodine intake. This condition is prevalent in
Hokkaido, and island in norther Japan, where dietary intake of iodine rich
seaweed and kelp are far in excess of RDA standards.
Research indicates that excess iodine may initially
induce acne-like skin lesions or worsen preexisting acne and can result in the
inhibition of thyroid hormone synthesis, with the effects being most pronounced
in patients with hyperthyroidism.
| RDA for men:
|| 110 - 150 mcg
| RDA for women:
|| 80 - 115 mcg
| RDA for
|| 60 - 110 mcg
| RDA for infants:
| RDA for pregnancy:
|| 125 mcg
| RDA for lactation:
|| 150 mcg
|| Prepackaged food
|| Fast food