What is iodine

Overview

Iodine is a chemical element discovered in 1811 by French chemist Bernard Courtois. It is the 53rd element on the periodic table and one of the heavier non-metallic elements. In its elemental form, iodine appears as a dark purple-black crystalline solid with a shiny metallic luster. One of its most distinctive properties is that it sublimates directly from solid to gas when heated, producing a characteristic violet-colored vapor.

Physical and Chemical Properties

Pure iodine is relatively rare and expensive to extract. Key properties include:

• Melting point: 113.7°C
• Boiling point: 184.4°C
• Color: Dark purple-black in solid form, violet vapor in gas form
• Reactivity: Less reactive than other halogens (chlorine, bromine, fluorine)
• Solubility: Slightly soluble in water but highly soluble in organic solvents

Role in Human Health

Iodine is a crucial micronutrient for human health, primarily because it is required to produce thyroid hormones (thyroxine and triiodothyronine). These hormones regulate metabolism, energy production, growth, and body temperature. Recommended daily intake: Adults need approximately 150 micrograms per day; pregnant women need 220 micrograms, and lactating women need 290 micrograms. The World Health Organization emphasizes iodine's importance for proper fetal and childhood brain development.

Dietary Sources

Iodine is naturally present in soil and seawater, making it available through various food sources. Rich sources include: seafood and seaweed (highest concentrations), dairy products (from iodine in cattle feed), eggs, and fortified grains. Many countries have reduced iodine deficiency by adding iodine to table salt, creating 'iodized salt.' This public health measure has significantly decreased the prevalence of iodine deficiency disorders globally.

Deficiency and Health Effects

Iodine deficiency remains a public health concern in many parts of the world, particularly in areas where soil iodine is low. Deficiency can cause goiter (thyroid enlargement), hypothyroidism, reduced growth, and severe intellectual impairment in children if untreated. Conversely, excessive iodine intake can cause thyroid problems in susceptible individuals.