While vitamin, mineral, protein and omega 3 fatty acid deficiencies often steal the spotlight for dietary intervention strategies for ADHD, there is another, less-heralded connection and treatment that deserves considerable attention. According to multiple journal articles, reviews and studies, there appears to be a correlation between an iodine deficiency and an increased likelihood of developing ADHD.
One such study on ADHD and iodine was published in the Journal of Endocrinology and Metabolism in 2004 by Vermiglio and coworkers. This study found that mothers who were iodine deficient were more likely to give birth to children with ADHD. While numerous nutritional deficiencies are often predominantly linked to Third World countries, Iodine deficiencies are surprisingly common in industrialized nations. Although little attention is often paid to this topic, the results of an iodine deficiency can be quite severe.
Since the thyroid gland and the hormones it secretes are heavily dependent on this key nutrient, low levels of iodine can lead to problems such as poor circulation and body temperature regulation, reduced energy levels, inhibited brain development and dysfunction, improper calcium levels in the blood and bones, and impaired immune function.
In a nutshell, the study examined the rates of ADHD in children who lived in 2 different regions, a relatively Iodine-rich region (where iodine deficiencies were more commonplace) and and Iodin-poor region. The 10-year study, which had a relatively small sample size, found that the rates of ADHD born to mothers at risk for facing an iodine deficiency was significantly higher than the rates of those born to mothers in a more iodine-sufficient environment. Furthermore, IQ scores were statistically lower in the low-iodine group.
We need to be careful not to lump ADHD into a general category of cognitive decline. After all, a very large percentage of individuals with the disorder are of average or above-average intelligence.
The overall mechanism of low iodine and the onset of ADHD is not completely clear, but there is a known correlation between low hormone levels (those secreted by the thyroid gland) and ADHD. Other studies, including one in the New England Journal of Medicine, have shown that individuals with a built-in resistance to thyroid hormones have higher incidences of ADHD. Individuals with a specific genetic mutation to the thyroid receptor-beta gene, are resistant to specific thyroid hormones and have roughly 3 times the risk of developing ADHD than the general population.
In the low iodine study, it appears that there was a bias towards hyperactive and impulsive behavior (as opposed to inattentive behavior), but with the small sample size used in the study, we should not put too much weight into this possible connection. Nevertheless, it is at least worth mentioning. Additionally, abnormal weight gain can also be a sign of an iodine deficiency, so an unexplained increase in weight accompanied by an increase in ADHD symptom severity may be due to an iodine deficiency and thyroid dysfunction.
Simple clinical tests can be done to determine whether an individual is iodine deficient and/or has thyroid dysfunction. One of the most common measuring devices is testing for the levels of TSH or Thyroid Stimulating Hormone. If an individual has underactive thyroid function (such as that caused by insufficient iodine intake), then the body tries to compensate for this by boosting thyroid function through increasing levels of TSH. Therefore, high levels of TSH correlate with an abnormally low thyroid function. Not surprisingly, in the pregnancy study on ADHD and iodine deficiency, mothers of ADHD children typically had elevated levels of TSH.
So how do we boost dietary iodine levels quickly and efficiently (the recommended daily amount is 150 micrograms, if that number means anything to you!)? One of the easiest ways is to replace common refined table salt with either iodized salt, or iodine-rich sea salt. Ocean fish and seaweed are also good bets as iodine-rich food sources.
One particularly good piece of information is that the developing fetus is surprisingly resilient to early stages of iodine deficiency in the mother if the iodine deficiency is corrected before the third trimester of pregnancy. Since the effects of an iodine deficient diet can be severe to both mother and child, I highly recommend pregnant mothers to switch to iodized salts or sea salt during the pregnant and nursing stages. This simple practice can significantly reduce the risk of ADHD and cognitive dysfunction in their child's future.