Thyroid Diseases and Diet

Thyroid Diseases and Diet

Thyroid diseases are one of the most commonly occurring diseases now a day. Thyroid gland is an organ situated in front of the neck. It secretes hormones called thyroid hormones (T4 and T3). These hormones are essential for maintenance of many vital functions of the body like controlling metabolism, growth, reproductive function, etc. Deficiency of thyroid hormone, medically labeled as hypothyroidism, is the most commonly encountered thyroid disorder. Deficiency of thyroid hormone usually occurs due to destruction of thyroid gland by autoimmune mechanism where the bodies’ own immune system perceives the gland as foreign organ and self destroys it. Hypothyroidism is treated by substituting thyroid medications. If the deficiency of thyroxine is significant one has to take lifelong replacement of this hormone to remain healthy. Thyroxine replacement is the main stay of therapy for hypothyroidism throughout the world.

Those suffering from thyroid disorders are often advised a long list of dietary restrictions. Hypothyroid persons are often advised to avoid cruciferous vegetables. Common cruciferous vegetables are cabbage, broccoli and cauliflower. Cruciferous vegetables contain phytonutrients (called glucosinolates) that are converted to thiocyanates which interfere with thyroid hormone synthesis. These substances are called goitrogens and are in excessively large amounts can produce goiter. However, that usually happens in exceptional circumstances. One such situation has been found in certain tribal population in parts of Central Africa where cassava root and cassava flour are staple foods and excessive amounts of thiocyanates in cassava especially when accompanied by deficiency of dietary selenium has been documented to impair with thyroid function.

It’s often doubted that regular intake of cruciferous vegetables can increase the risk of thyroid problems. The answer here is no; there is no research to show that regular intake of cruciferous vegetables in ordinary dietary amounts poses any unwanted risk to the thyroid. In fact, there are many well-documented health benefits from daily consumption of cruciferous vegetables, including decreased risk of colorectal cancer. Besides, cooking these vegetables reduces the effect that cruciferous vegetables have on the thyroid gland.  Thus, occasional intake of cabbage or cauliflower is very unlikely to interfere with thyroid function and there is no medical evidence to suggest avoidance of these vegetables.

Soy food and soya beans contain isoflavone, a substance theoretically known to interfere with thyroid hormone synthesis. But analysis of available medical data shows that there is little evidence to suggest that soy foods, or isoflavones adversely affect thyroid function in persons who are euthyroid (someone who has a normally functioning thyroid gland). In contrast, some evidence suggests that soy foods, by inhibiting absorption, may increase the dose of thyroid hormone required by hypothyroid persons. In addition, there remains a theoretical concern based on in vitro and animal data that in individuals with compromised thyroid function and/or whose iodine intake is marginal soy foods may increase risk of developing clinical hypothyroidism. Therefore, it is important for soy food consumers to make sure their intake of iodine is adequate. Medical literature or guidelines do not make any recommendations to avoid soy products in hypothyroid persons.

Iodine supplements usually aren’t necessary in Indian scenario. Previously, when iodinization of salt was not mandatory in India, iodine deficiency used to be the most common cause of hypothyroidism. It is true that severe iodine deficiency can cause hypothyroidism. But iodine deficiency in India is now rare since the addition of iodine to salt (iodized salt) and other foods. If iodine deficiency isn’t the cause of hypothyroidism, then iodine supplements provide no benefit. Thyroxine replacement in appropriate dosage remains the most effective and safe treatment option for hypothyroidism.  

Persons with hypothyroidism often have difficulty in losing weight. It should be kept in mind that once a person with hypothyroidism is receiving an adequate dose of thyroxine, failure to lose weight is more related faulty dietary pattern and lack of exercise rather than thyroid disorder itself.

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