Hashimoto’s thyroiditis is an autoimmune disease that destroys thyroid cells by inflammation and antibody immune processes. It is the most common cause of hypothyroidism in developed countries. But in contrast, worldwide, the most common cause of hypothyroidism is an inadequate dietary intake of iodine.
Goitrogens: friend or foe?
Goitrogens are foods that interfere with thyroid hormone production by interfering with iodine uptake. When not enough iodine is available, the thyroid cannot produce sufficient levels of thyroid hormones T4 and T3. The hypothalamus senses low T4 and releases TSH-thyroid releasing hormone, which triggers the pituitary gland to produce more TSH. The thyroid gland responds to TSH by making more hormones. If it can’t keep up with demand, the thyroid grows bigger causing a goiter (swelling in the neck). What sounds terrible for our thyroid is actually not such a bad thing for those with Hashimoto’s disease.
- Cruciferous vegetables: kale, cabbage, broccoli, turnips, brussel sprouts, collard greens
- Cassava, lima beans, sweet potato, sorghum
- Soy, millet
By blocking iodine uptake, goitrogens are actually beneficial to those with hashimoto’s thyroiditis by lowering antibody activity within the thyroid gland. Goitrogenic foods have also been found to increase glutathione levels which lower oxidative stress in the gland to slow the rate of destruction of the thyroid cells.
*It’s also important to note: chemical goitrogens are not beneficial for Hashimoto’s or decreasing antibodies and oxidative stress in the thyroid (antibiotics, pesticides, NSAIDS, lithium, benzodiazapenes, thyocyanate from cigarettes)
In a 2 year 2014 study, researchers concluded that Iodine restriction may normalize or, at the very least, decrease serum TSH levels in hypothyroid patients. Therefore, restriction of iodine intake could be a primary treatment option in patients with high TSH with or without antibodies [in countries that are not experiencing iodine-deficiency].
An iodine restrictive diet can assist in lowering thyroid antibodies in Hashimoto’s and normalize TSH levels. In this study, 78% returned to normal thyroid function with only iodine restriction over 3 months without thyroid hormone replacement.
Iodine restriction diet (less than 100ug/day):
Foods containing iodine
- iodized salt
- seasoning mixes with iodized salt
- onion salt, garlic salt etc made with iodized salt
- seaweed (kelp, nori, kombu, wakami)
- food additives: carrageen, iodides, alginates, iodate
- egg yolks
- most seafood except fresh-water fish
- multi-vitamins (look for those that leave iodine out, like Pure Encapsulations Nutrient 950)
- red dye #3
The Goldilocks effect…
If you have hypothyroidism without antibodies, it is still important to be mindful that too little or too much iodine can be detrimental to your thyroid health. We only need small amounts of iodine for proper thyroid health and preferably through clean food sources from the list above.
Soy and thyroid function
Soy consumption has also been recently downgraded from a highly avoided food source for those with thyroid disease to now a more neutral choice. There was evidence in the past that suggested that soy was associated with thyroid disorders such as hypothyroidism, goitre, and autoimmune thyroid disease. But according to a 2019 systematic review and meta-analysis published in Scientific Reports, soy has no effect on Free T3 & Free T4 thyroid hormones. The researchers looked at 18 randomised, controlled trials from studies that involved the effects of soy on free triiodothyronine (freeT3), free thyroxine (freeT4) and thyroid stimulating hormone (TSH). Included in this study was the 2015 European Food Safety Authority risk assessment of the effect of soy protein and soy isoflavones on thyroid function. The EFSA also concluded soy isoflavones did not affect thyroid function.
Of course, if you choose to consume soy products, please only include non-GMO, organic soy. Choosing fermented soy, like miso, can be part of a more traditional, whole food diet.
Since you have your own individual biochemistry, it is always a good idea to follow your thyroid panel including TSH, FT3, FT4 and TPO antibodies while trying new diets and supplements.