(Iodine Boosted American’s IQ)
(There are reasons we have a little more iodine than most others in our Foundation multi-vitamin, mineral, etc. We discuss other reasons in our ingridients article, however, we thought this might be worthy of individual attention. Excerpts are from Discover, July, 2013.)
Iodized salt is so commonplace in the U.S. today that you may never have given it a second thought. Iodine deficiency today is the leading cause of preventable mental retardation in the world. It’s estimated that nearly one-third of the world’s population has a diet with too little iodine in it. The problem isn’t limited to developing countries as about one-fifth of those cases are in Europe where iodized salt is still not the norm.
Now, new research finds that humble iodine has played a substantial role in cognitive improvements seen across the American population in the 20th century.
Iodine is a critical micronutrient in the human diet that our bodies can’t synthesize. We have to rely on food to obtain it and it’s been added to salt (in the form of potassium iodide) since 1924. Originally, iodization was adopted to reduce the incidence of goiter, an enlargement of the thyroid gland. Research since then has found that iodine also plays a crucial role in brain development, especially during gestation.
Iodine’s Natural Experiment
With this background, a group of researchers noticed a difference in children. They compared the intelligence of children born just before 1924 (the year iodization began) and those born just after.
War recruits all took a standardized intelligence test as part of their enlistment. The researchers didn’t have access to the test scores themselves, but they had a clever substitute: smarter recruits were assigned to the Air Forces while the less bright ones went to the Ground Forces. This allowed the researchers to infer test scores depending on which branch a recruit was selected for.
Intelligence data were paired with birthdate and hometowns since iodine levels in the soil and water vary significantly from place to place. To estimate which regions were naturally high-iodine and which were low, the researchers referred to nationwide statistics collected after World War I on the prevalence of goiter.
In all, researchers had sufficient data on about 2 million male recruits born between 1921 and 1927.
The economists found that in the lowest iodine areas – the bottom quarter of the study population – the introduction of iodized salt had huge effects. Men from these regions born in 1924 or later were significantly more likely to get into the Air Force and had an average IQ that was 15 points higher than their predecessors.
Nationwide, that averages out to a 3.5-point rise in IQ because of iodization, the researchers report in a paper for the National Bureau of Economic Research.
Introducing iodine should be gradual as sudden iodine supplementation among deficient people can have side effects. However, on the positive side, iodine’s mental benefits may even help explain the Flynn Effect, which observes that IQ rose about 3 points per decade in developed countries throughout the 20th century.
It’s been thought that improved health and nutrition were the driving forces of the Flynn Effect. Now, it appears that iodine alone was responsible for roughly one decade of that remarkable climb. All the more reason, then, for the rest of the world to follow suit and relegate iodine deficiency to the history books.
This is one more reason for having a bit more than average iodine in our multi-vitamin / mineral Foundation.