Goiter is an enlargement of the thyroid gland that often produces a noticeable swelling in the front of the neck.
This enlargement can be caused by iodine deficiency, inability of the body to use iodine correctly, or a variety of thyroid disorders, including infection, tumors, and autoimmune disease. Some environmental pollutants, heavy metal poisonings, and certain drugs can also contribute to goiter formation.1 2 3 Both iodine deficiency and inability to use iodine properly make the thyroid gland unable to produce thyroid hormone, a hormone that helps to regulate the body’s metabolic rate. This state is called hypothyroidism and the symptoms include fatigue, weight gain, heavy menstrual bleeding in women, dry skin and hair, as well as goiter.
Iodine-deficiency goiter can be common in regions where the soils and foods have insufficient iodine. Preschool children, adolescent girls, pregnant women, and the elderly are most vulnerable to goiter and other iodine-deficiency disorders.4 Areas where iodine supplies are inadequate see high rates not only of goiter but also of birth defects and retardation of both mental and physical development.5 While iodine deficiency is the leading cause of goiter worldwide, it is a rare cause of goiter in the developed world. For this reason, any goiter that occurs in the developed world must be evaluated by a healthcare provider and its cause determined before any treatment is given.
What are the symptoms of goiter?
People with goiter may notice a soft swelling in the front of the neck.
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.
Nutritional supplements that may be helpful for goiter
Iodine supplementation can be an effective treatment of iodine deficiency hypothyroidism and can halt the growth of goiter if the cause is not complicated by malnutrition or environmental and dietary goitrogens.39 40 Iodine supplements will help to shrink goiters during early stages, but they have no effect in later stages.41 Ingestion of 2,000 to 6,000 mcg of iodine daily over long periods of time can be toxic to the thyroid and can be a cause of goiter.42 43
Blood levels of vitamin A are lower in people with goiter than in similar people without goiter.44 45 The same relationship has been found for vitamin E and goiter.46 Animal research has found that, in iodine-deficient conditions, a supplement combination of vitamin C, vitamin E, and beta-carotene prevented goiter formation (though hypothyroidism was not improved), and vitamin E alone had a similar effect.47 No studies have been done to investigate this benefit in humans.
When iodine deficiency is present, other nutrient levels become important in the development of goiter. Deficiencies of zinc48 and manganese49 can both contribute to iodine-deficiency goiter; however, an animal study found that manganese excess can also be goitrogenic.50 It has been suggested that selenium deficiency may contribute to goiter.51 However, when selenium supplements were given to people deficient in both iodine and selenium, thyroid dysfunction was aggravated, and it has been suggested that selenium deficiency may provide some protection when there is iodine deficiency.52 53 A study of the effects of selenium supplementation at 100 mcg daily in women without selenium deficiency but with slightly low iodine intake found no effect on thyroid function.54 The authors concluded that selenium supplementation seems to be safe in people with only iodine deficiency but not in people with combined selenium and iodine deficiencies. In those cases, iodine supplementation has been shown to be most useful.55 No studies have been done to evaluate the usefulness of supplementation with zinc or manganese to prevent or treat goiter.
Are there any side effects or interactions with goiter?
Refer to the individual supplement for information about any side effects or interactions.