Introduction:
Iodine is a vital trace element required at all stages of life especially during formative years. It is important to sustain the daily functions of human body and deficiency or excess can have significant adverse effects on the body. Iodine is a non-metal, typically found and function in its ionic form iodide (I¯).
Why You Need Iodine?
How much iodine do I need?
The amount of iodine you need each day depends on your age. Average daily recommended amounts are listed below in micrograms (mcg).
Recommended Dietary Allowance
- Birth to 6 months 110 mcg
- Infants 7–12 months 130 mcg
- Children 1–8 years 90 mcg
- Children 9–13 years 120 mcg
- Teens 14–18 years 150 mcg
- Adults 150 mcg
- Pregnant teens and women 220 mcg
- Breastfeeding teens and women 290 mcg.
Sources:
The iodide concentration in foods is extremely variable because, it reflects the regionally variable soil concentration of the element and the amount and nature of fertilizers used in plant cultivation.
❖ The iodide content of grains, vegetables, and fruits varies with the iodide content of the soil, and iodide content of meat depends on the iodide of the soil and plants that the animals ate.
❖ Amount of the iodide in drinking water is an indication of the iodide content of the rocks and soils of a region.
❖ Iodide is found in seafoods, however large differences exist between marine fish and freshwater fish.
❖ Edible marine fish contain about 30-300 µg of iodide/100 g
❖ In addition to seafoods, dairy products represent a major source of iodide in the American diet.
❖ Breads (due to addition of iodates, IO³¯) also serves as a source of dietary iodide.
❖ Iodized salt (¼ teaspoon) supplies about 70 µg of iodide.
Digestion and Absorption
During digestion organic bound iodine (iodine bound to amino acids) is released and converted into iodide and iodates for example from breads or iodized salts is usually reduced to iodide by glutathione within GIT.
Mainly absorbed as iodide, mostly from the stomach and to a lesser extent from duodenum.
The thyroid gland traps iodide by active transport system against iodide gradient. The thyroid gland contains 70-80% of the total body iodide and takes up about 120 µg iodide/day.
Main Functions of Iodine
The main function of iodide is in the synthesis of thyroid hormone thyroxine(T4) and triiodothyronine (T3). Thyroid stimulating hormone also called thyrotropin, released from the pituitary gland, helps to regulate thyroid hormone production and secretion.
Four atoms of iodide are needed for each T4 and three atoms of iodide for each T3.
Physiological Effects of Thyroid Hormone
The effects of thyroid hormone on metabolism are many and varied.
- Regulate the rate at which calories are burned, affecting weight loss or weight gain.
- Can slow down or speed up the heartbeat.
- Can raise or lower body temperature.
- Influence the rate at which food moves through the digestive tract.
- Control the way muscles contract.
- Control the rate at which dying cells are replaced.
- Stimulates oxygen consumption and basal rate of metabolism.
Directly or indirectly, most organ system are under the influence of these hormones.
Excretion:
Kidney have no mechanism to conserve iodide so they provide major route (~80-90%) for iodine excretion. Some iodide may also loss in sweat.
