To Summarize:

• Goitrogens are substances which may interfere with thyroid function
• They may interfere with the thyroid gland and how the thyroid hormones are made
• Certain foods contain dietary goitrogens. Those foods are otherwise healthy, good foods.
• People with low functioning thyroid need to be aware of these, and may need to avoid them

Thyroid Function

Proper thyroid gland function and hormone metabolism is key for optimal health. Those suffering from Hashimoto’s Thyroiditis (a form of hypothyroidism) have autoimmune destruction, but treatment must also focus on thyroid hormone metabolism. For a complete review of healthy thyroid function, please click here.

What are Goitrogens?

Goitrogens are agents found in the environment that are known to interfere with thyroid gland function. There are strictly environmental factors (such at chemicals, medications and more) in addition to dietary sources of goitrogens [1].

Goitrogens work by interfering with iodine utilization by the thyroid gland. Goitrogens get their name because these compounds may be responsible for the development of a physical goiter. About 5% of the world’s population have goiters, many of which are from underdeveloped nations, where iodine deficiency is more prevalent. However, more than 150 million individuals worldwide with goiters live in highly developed countries, despite iodine prophylaxis [2].

Goitrogens work by [2]:

• Directly working on the thyroid gland
• Indirectly alternating regulatory mechanisms of the thyroid gland and the peripheral metabolism and excretion of thyroid hormones [2]

Goitrogens Found in the Diet

Cassava, lima beans, linseed, sorghum, sweet potato

• Contain cyanogenic glucosides; they are metabolized to thiocyanates that compete with iodine for thyroidal uptake [3]

Cruciferous vegetables: cabbage, kale, cauliflower, broccoli, turnips, rapeseed

• Contains glucosinolates; metabolites compete with iodine for thyroidal uptake [3]

Soy and soybean products

• Flavonoids impair thyroid peroxidase activity [3]
• Soy or soy enriched foods can aggravate thyroid problems reducing T4 absorption and interfering with thyroid hormone action [4]
• Evidence of goiter growing in infants (10-month) being fed soybean products right from birth (versus breast milk or formula). To reverse stop soybean and add Lugol’s iodine drops [4]
• Review of 14 trials: soy protein and isoflavones do not affect normal thyroid function in people with sufficient iodine intake, but they may interfere with absorption of synthetic thyroid hormone (Synthroid), increasing the dose of medication in hypothyroid patients [4]

Cyanogenic Plant Foods: Cauliflower, cabbage, mustard, turnip, radish, bamboo shoot, cassava

• Raw, boiled, cooked extracts of certain plant foods are shown to posses anti-TPO activity [4]
• Boiled extracts of these plant foods showed highest anti-TPO potency, followed by cooked and raw [4]

Millet

• Rat studies: millet containing diets produce effects resembling small doses of anti-thyroid drug methimazole [2]