Читать книгу Anti-Aging Therapeutics Volume XIV - A4M American Academy - Страница 58

Iodine is abundant in soil and sea water, but regional levels vary tremendously based on past snow, rain, and glaciation, all of which leach it to the ocean. Many regions of the world have been known as ‘goiter belts’ due to the low soil iodine and high prevalence of goiters, such as the Great Lakes Region, the Himalayas, the Andes, and the Alps. Goiters in these regions were especially common when nearly all food was locally grown.

This regional variation in goiters is due to the fact that the amount of iodine found in plants varies with the concentration of iodine in the soil. For example, plants grown in iodine-rich soil average 1 mg iodine per kg of dry weight, while those grown in iodine deficient soil may have levels as low as 0.01 mg/kg. Since iodine is abundant in seawater, nearly all foods from the sea are rich in it.¹³

Iodine fortification of salt, which began in 1924 in the U.S., has all but eliminated goiters here. For example, 4-years after iodine fortification of salt, the rate of goiters in Michigan schools reduced from 40% to 10%. A few years later the rate was down to 1.4%.¹⁴

Regions with poor soil iodine have been especially hard hit when selenium is also lacking. Selenium is a critical cofactor for type 1 deiodinase, which converts T4 to T3. It is also critical for formation of glutathione peroxidase which protects the thyroid from oxidative stress.¹⁵