Goiter

Dietary changes that may be helpful for goiter

The most important dietary concern in treating iodine-deficiency hypothyroidism and preventing goiter is ensuring adequate intake of iodine. Iodine is found naturally in foods from the ocean, such as fish and seafood, kelp, and sea vegetables, and in plant and animal products produced in areas where soil and water contain sufficient iodine.^{6 7} In developed countries, commercial table salt has been fortified with iodine since the 1920s to prevent deficiency.⁸ Iodized salt contains approximately 100 micrograms of iodine per gram of salt. This fortified salt is used directly and is incorporated into animal feeds and processed foods making it easy to achieve the Recommended Dietary Allowance (RDA) of 150 mcg for adolescents and adults and 200 mcg daily for pregnant and breast-feeding women.⁹ Iodized salt has proven so effective it is recommended as the intervention of choice to eliminate iodine deficiency worldwide.^{10 11} Iodized oils, given as an annual injection or as food by mouth, have also been used effectively to treat iodine-deficiency goiter.^{12 13}

Although iodine deficiency and goiter are now quite uncommon in developed countries, recent studies have found that the average dietary iodine intake in the United States has fallen below RDA guidelines.¹⁴ Long-term excessive dietary intake of iodine (1,000 to 2,000 micrograms daily), while less common than iodine deficiency, can occur in people who eat large amounts of kelp and other sea vegetables and can also cause goiter.^{15 16}

A number of commonly eaten foods have been shown to interfere with the use of iodine by the thyroid, thus reducing production of thyroid hormone and causing goiter. These foods, known as goitrogens, include vegetables in the Brassica family such as broccoli, cabbage, kale and mustard,¹⁷ millet,¹⁸ soybeans,¹⁹ pine nuts²⁰ and some seed meals used in animal feeds.^{21 22} These foods can be safely eaten in moderate amounts by people who consume adequate iodine.²³ A combination of low iodine intake and high intake of goitrogenic foods increases the likelihood of goiter.^{24 25}

Nutrient deficiencies, including zinc,²⁶ manganese²⁷ and vitamin A,^{28 29} and severe protein malnutrition³⁰ also contribute to an inability to use iodine well and to the development of goiter.^{31 32} In the presence of adequate iodine supplies, it is less common for such factors to cause goiter;^{33 34} however, when iodine intake becomes deficient, even mild malnutrition can have such a negative impact on thyroid function.^{35 36} High levels of minerals such as calcium and magnesium, and certain bacteria in drinking water, have also been shown to be goitrogenic.^{37 38} Therefore, proper nutrition and a healthy water supply are crucial in the prevention and treatment of goiter.