Iodine Fortification

Reference from the joint report of FAO/WHO expert consultation on Human Vitamins and Minerals verbatim.

Iodine Fortification

Benmiloud, M., Bachtarzi, H. & Chaouki, M.B. 1983. Public health and nutritional aspects of endemic goitre and cretinism in Africa. In: Delange F., Ahluwalia R. (eds) Cassava toxicity and thyroid. p. 50. Research and Public Health Issues, IDRC, Ottawa.

Iodine deficiency is present in almost all parts of the developed and developing world, and environmental iodine deficiency is the main cause of iodine deficiency disorders. Iodine is irregularly distributed over the earth’s crust, resulting in acute deficiencies in areas such as mountainous regions and flood plains. The problem is aggravated by accelerated deforestation and soil erosion. 

Upper Limit of Iodine Intake for Different Age Groups

Reference from the joint report of FAO/WHO expert consultation on Human Vitamins and Minerals verbatim.

Roti, E. & Vagenakis, AG. 1996. Effect of excess iodide : clinical aspects. In: Braverman L.E., & Utiger R.D. eds. Thyroid. p. 316-327. Philadelphia, JB Lippincott.

An iodine excess also can be harmful to the thyroid of infants by inhibiting the process of synthesis and release of thyroid hormones (Wolff-Chaikoff effect).

Delange, F. 1994. The disorders induced by iodine deficiency. Thyroid, 4: 107-28. 

The threshold upper limit of iodine intake (the intake beyond which thyroid function is inhibited) is not easy to define because it is affected by the level of iodine intake before exposure to iodine excess. Indeed, long-standing moderate iodine deficiency is accompanied by an accelerated trapping of iodide and by a decrease in the iodine stores within the thyroid.

Iodine Requirements in Infancy

Reference from the joint report of FAO/WHO expert consultation on Human Vitamins and Minerals verbatim.

Iodine requirements in infancy

Delange, F., Bourdoux, P., Chanoine, J.P. & Ermans, A.M. 1988. Physiopathology of iodine nutrition during pregnancy, lactation and early postnatal life. In: Vitamins and minerals in pregnancy and lactation. Berger, H., eds., New York, Raven Press, Nestle Nutrition Workshop Series, 16: 205-13.

Gushurst, C.A., Mueller, J.A., Green, J.A. & Sedor, F. 1984. Breast milk iodide: reassessment in the 1980s. Pediatrics, 73: 354-57.

The US recommendation of 40 μg/day for infants aged 0–6 months (or 8 μg/kg/day, 7 μg/100 kcal, or 50 μg/l milk) is probably derived from the observation that until the late 1960s the iodine content of human milk was approximately 50 μg/l and from the concept that nutrition of the human-milk-fed infant growing at a satisfactory rate has been the standard against which nutrition requirements have been set.

Dietary Sources.

Reference from the joint report of FAO/WHO expert consultation on Human Vitamins and Minerals verbatim.

Dietary sources

Koutras, D.A., Matovinovic, J. & Vought, R. 1985. The ecology of iodine. In: Stanbury

J.B., Hetzel B.S. (eds). Endemic goitre and cretinism, iodine nutrition in health and disease. p. 185-95.New York: Wiley Eastern Limited.

The iodine content of food depends on the iodine content of the soil in which it is grown. The iodine present in the upper crust of earth is leached by glaciation and repeated flooding and is carried to the sea. Sea water is, therefore, a rich source of iodine. The seaweed located near coral reefs has an inherent biologic capacity to concentrate iodine from the sea. The reef fish which thrive on seaweed are rich in iodine. 

Overview of Significant Scientific Information

Reference from the joint report of FAO/WHO expert consultation  on Human Vitamins and Minerals verbatim.

Shankar, A.H. & Prasad A.S. 1998. Zinc and immune function: the biological basis of

altered resistance to infection. Am. J. Clin. Nutr., 68(suppl.): 447S-463S

All biologic actions of iodide are attributed to the thyroid hormones. The major thyroid hormone secreted by the thyroid gland is T4 (tetra-iodo-thyronine). T4 in circulation is taken up by the cells and is de-iodinated by the enzyme 5' prime-mono-de-iodinase in the cytoplasm to convert it into tri-iodo-thyronine (T3), the active form of thyroid hormone. T3 traverses to the nucleus and binds to the nuclear receptor. All the biologic actions of T3 are mediated through the binding to the nuclear receptor, which controls the transcription of a particular gene to bring about the synthesis of a specific protein.

Summary of the Human Metabolic Processes Requiring Iodine

FAO/WHO and from other sources...verbatim

Stanbury, J.B. 1950. Physiology of endemic goitre. In: Endemic Goitre. p. 261-262. Geneva. World Health Organization.

At present, the only physiologic role known for iodine in the human body is in the synthesis of thyroid hormones by the thyroid gland. Therefore, the dietary requirement of iodine is determined by normal thyroxine (T4) production by the thyroid gland without stressing the thyroid iodide trapping mechanism or raising thyroid stimulating hormone (TSH) levels.