~2838–2700 BC — Emperor Shen-Nung of China

The Chinese Emperor Shen-Nung, commonly revered as the ancestor of herbal medicine in China, is credited with prescribing seaweed as an effective remedy for goiter. His observations and prescriptions were among the earliest to codify iodine-based treatment, and the relationship between goiter and seaweed is traced to his era, around 2700–2838 BC. While initially transmitted orally, these observations were later formally documented in the Sheng Nong’s Herbal Classic around 300 BC.

~300 BC — Shen-Nung’s Herbal Classic

The oral tradition surrounding seaweed and goiter treatment was formally committed to writing in the Shen Nung’s Herbal Classic (also known as the Shennong Bencao Jing) around 300 BC. This text, compiled during the Qin–Han dynasties, recommended seaweed for the treatment of goiter disease, described as “Ing-Liou.” Seaweed was noted to “soften” thyroid nodules and relieve associated swelling. This constitutes one of the earliest written pharmacological records in history.

~1400 BC — Ayurvedic Medicine (India)

Ayurvedic medical texts from approximately 1400 BC, native to India, also referenced goiter — described as “galaganda” — and included treatments drawing on iodine-rich marine sources, further demonstrating the broad and independent recognition of iodine’s therapeutic role across ancient civilizations.

Classical Antiquity 700 BC - 400 AD

The use of iodine-rich seaweed and burnt sponge for goiter treatment spread westward and was documented by prominent Greek and Roman physicians, including Hippocrates and Galen, as well as later medieval writers such as Roger and Arnold of Villanova.

These treatments remained in consistent use across cultures for millennia, affirming their effectiveness even without an understanding of the underlying mechanism.

1811

French chemist Bernard Courtois first isolated iodine as an element in 1811 while processing seaweed ash during gunpowder production. He observed a distinctive violet vapor, and the element was subsequently named “iodine” by Gay-Lussac, from the Greek ioeides, meaning violet-colored.

This discovery provided the scientific explanation for why seaweed-based treatments had been effective for thousands of years.

1819

Swiss physician J.F. Coindet, aware of the traditional use of seaweed in treating goiter, hypothesized that iodine was its active ingredient.

In 1819, he successfully tested a tincture of iodine on 150 patients, achieving significant reduction in goiter size within one week. This marks the first time iodine was consciously and deliberately administered as iodine in a clinical setting.