Iodine Supplementation: Should it be considered for people consuming vegetable-based diets?

In 2009, I wrote an article on evidence supporting iodine supplementation during pregnancy (1). Iodine intake has decreased over the last 30 years (primarily due to decreased consumption of iodized salt and dairy products), and studies show that maternal iodine supplementation has beneficial effects on neurocognitive development of infants. I am happy to report that the Council for Responsible Nutrition recently released a guideline recommending for dietary supplement manufacturers and marketers to include a daily serving of at least 150 micrograms iodine in all multivitamin/mineral supplements intended for pregnant and lactating women in the United States (2). If dietary supplement manufacturers follow this guideline, pregnant or lactating mothers who take prenatal supplements should receive an adequate intake of iodine.

Iodine is an essential component of triiodothyronine (T3) and thyroxine (T4), which regulate cell activity in virtually all tissues, and are responsible for maintenance of metabolic processes. Adequate iodine is required for optimal thyroid function throughout life, not just during development. Symptoms of iodine insufficiency in adults include slower response times, impaired mental function, fatigue, weight gain, cold intolerance, and constipation (3). Many of these symptoms are associated with aging, so iodine deficiency may be overlooked in older people.  As consumption of iodine is waning, it is time to take a fresh look at consumption of iodine in segments of the population who may be at risk of iodine deficiency: vegans, vegetarians and omnivores consuming very little meat or dairy products. With a few exceptions (e.g. seaweed, prunes) (4), vegetables and fruits are notoriously poor in iodine. Vegans with low iodine intake are particularly vulnerable to hypothyroidism because goitrogenic substances found in cruciferous vegetables and soy have been shown to inhibit thyroid