It seems that optimizing selenium intake provides powerful protection against autoimmune thyroid disease, and provides tolerance of a wide
range of iodine intakes.
Based on the reported values in seaweed, some have claimed levels of 12 mg (12,000 mcg) in Japanese diets, although a published analysis
of iodine intake in Japan found a range of 45 - 1921 mcg per day (J Nutr Sci Vitaminol (Tokyo).
In individuals with anti-thyroid peroxidase (TPO) or anti-thyroglobulin (TG) antibodies, the incidence of elevated TSH increased with greater
levels of iodine intake (18).
Iodine is particularly important for pregnant women; in places like the United Kingdom, where table salt is not fortified with iodine, women rely on dairy for
much of their iodine intake.
Excess iodine intake in the mother may block thyroid function in the fetus, leading to hypothyroidism and goitre, and is associated with poorer mental and psychomotor development or behaviour problems in children.22 56 64 However, the risk for adverse effects of iodine supplementation is higher in cases of preconception ID due to sudden
increase of iodine intake, and should therefore not be the case in Sweden where the normal population is iodine sufficient.65
With optimal selenium status, thyroid follicles are healthy, goiter is eliminated, and autoimmune markers like Th1 / Th2 ratio and CD4 + / CD8 + ratio are normalized over a wide
range of iodine intake.