PREVENTION OF ATTENTION-DEFICIT HYPERACTIVITY DISORDER?
Emerging data from research conducted over the past 15 years suggest a possible link between low maternal iodine status and increased risk of ADHD in the offspring. According to a report published in 2004, 11 of 16 children born to women living in a moderately iodine-deficient region in Italy developed ADHD compared to no offspring from the 11 control mothers living in a marginally iodine-deficient region.
On the other hand, another group of researchers investigated whether T4 levels at birth could represent a biomarker for later development of ADHD and found that all newborns in the sample had T4 within the normal range and no correlation between values and risk could be demonstrated. This evidence invalidated TSH levels as a biomarker of risk, but does not disprove a link between iodine and ADHD, as earlier studies found that those newborns who later developed ADHD were all euthyroid at birth.
Although further investigation is required to clarify these observations, they have provided a new avenue for ADHD research.
FIBROCYSTIC BREAST DISEASE AND CYCLIC MASTALGIA
A 1993 review that focused on three clinical studies suggests that iodine supplementation may improve objective and subjective outcomes, including pain and fibrosis, for women with fibrocystic breast disease and cyclic mastalgia. Together the trials involved 1000 women and used a variety of different forms, the most successful being molecular iodine at a dose of 0.08 mg/kg (approximately equivalent to 500 µg/day in a 60 kg woman).
Recently a placebo-controlled trial conducted with 11 euthyroid women with cyclic mastalgia tested different doses of molecular iodine ranging from 1.5 to 6 mg/day and showed that after 3 months of treatment, 50% of patients consuming 3 or 6 mg/day experienced a significant decrease in pain. Although no dose-related adverse events were detected, further investigation is required to confirm both efficacy and safety.
There is suggestive evidence of a preventive role for iodine in breast cancer. As far back as 1896 research has suggested a link between iodine deficiency, thyroid disease and breast cancer. More recently, epidemiological data have demonstrated a correlation between increased incidence of breast cancer and a range of thyroid conditions, most notably hypothyroidism. In addition, the observed low rates of breast cancer in Japan are speculated to be partly due to a high dietary iodine intake, further suggesting a protective effect.
It is noteworthy that both the thyroid and the breast share the capacity to concentrate iodide, which exerts an antioxidant effect and protects cells from peroxidative damage. Whereas the thyroid retains this capacity throughout life, the breast can only concentrate iodide during pregnancy and lactation, states associated with a reduced risk of breast cancer. It has been theorised that with iodine insufficiency during pregnancy and lactation, the protective effect of iodide may be compromised, concomitant with diminished antioxidant activity. Researchers speculate that this scenario may be compounded by coexisting selenium deficiency.
Besides the diminished antioxidant effect, studies with animal models show that iodine deficiency results in changes in the mammary gland that makes it more sensitive to the effects of oestradiol. Oestradiol stimulates cell division, which eventually results in cyst formation, and dietary supplementation with iodine can improve these alterations.
At present the only interventional evidence comes from studies of rats, which found that administration of Lugol’s iodine or iodine-rich Wakame seaweed suppressed the development of induced mammary tumours and rigorous human studies are required.
Iodine-releasing tablets and iodine tincture have been used for many years to decontaminate water and have been used by the United States Army since WWII. A weak aqueous solution of 3-5 ppm of elemental iodine can destroy a wide range of enteroviruses, ameobae and their cysts, bacteria and their spores, as well as algae. Under temperate conditions of 25°C the disinfection process takes 15 minutes, longer in colder conditions. Adding to the versatility of iodine as a water decontamination agent is its ability to act over a wide range of pH and still be effective in the presence of ammonia and amino ions from nitrogenous wastes that may be also present in the water.
Iodine solution is widely used as a topical antiseptic in the treatment of superficial wounds. It is a highly effective method of decontaminating intact skin and minor wounds and has a low toxicity profile. Povidone-iodine preparations have replaced older iodine solutions and are now the most widely used form.
Although the treatment is considered safe, a number of recent reports of iodine toxicity in newborns receiving ongoing treatment with topical iodine-based solutions suggests that it should be used with caution as an ongoing treatment in this group and TSH monitoring considered where appropriate.