The problem: iodine deficiency
Iodine is a micronutrient crucial for bone and brain development. However around 1.75 billion people — nearly a quarter of the world’s population — get too little iodine in their food.   This leads to increased rates of miscarriage, stillbirth, and infant mortality, as well as cognitive and developmental problems, goiter, and hypothyroidism. Iodine deficiency is the leading preventable cause of intellectual and developmental disabilities in the world.
Huge progress has been made to address iodine deficiency through universal salt iodization (USI). The number of iodine deficient countries was reduced from 55 in 2003 to just 19 in 2017.  Yet despite many years of effort, about 25% of households in the developing world are still iodine deficient — many of them in areas that are the poorest and hardest to reach.
The solution: new models of universal salt iodization — or USI
We are in an unprecedented position: on the verge of being able to control iodine deficiency at a population level in a sustainable way. The good news is that fortifying salt with iodine is safe, relatively easy, has high returns on investment, and is extremely inexpensive. It is one of the most common forms of fortification, now practiced in more than 160 countries.
Adding potassium iodate to household salt during the production process gives people access to adequate iodine in their diet. (Salt fortification is credited with preventing 750 million cases of goiter over the past 25 years  and, according to Prof. Michael Zimmerman, Chair of Iodine Global Network, “89 studies worldwide have shown that salt iodization leads to an 87% decrease in cretinism and a 73% decrease in low IQ.”)
While most large salt producers do this routinely, many small- and medium-sized producers in the developing world lack the means or knowledge to do so. Adapting USI models to include these smaller producers is needed to ensure full and sustained coverage. That’s where GAIN comes in.
How Global Alliance for Improved Nutrition works
GAIN has been a major force in global USI programs since 2008, when it was established in partnership with UNICEF and funded by the Bill and Melinda Gates Foundation. They support governments and salt producers in establishing and sustaining secure supplies of potassium iodate, improving iodization quality, effectively implementing salt quality laws, and putting monitoring systems in place.
GAIN can help build, expand, or sustain salt iodization programs depending on the country and the level of support it needs. It takes an investment of just US$0.15–$0.40 for GAIN to help provide one person access to adequately iodized salt through their lifetime. 
In 2018, GAIN systematic review and meta-analysis of 50 studies which GAIN commissioned helped fill a critical knowledge gap about the full impact of salt iodization programs in low- and middle-income countries. It found that there was a 74% reduction in the odds of goitre and a significant reduction in iodine deficiency.