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Diet and Endocrine Disrupting Chemicals on the Thyroid

Update on the role of diet and endocrine disrupting chemicals on the thyroid.

Thyroid dysfunction is on the increase and unfortunately is not always picked up with standard pathology testing that looks at TSH, T3 and T4. Often these primary parameters are within limits on serum testing but patients exhibit thyroid symptoms. It is not until thyroid antibodies are conducted or ultrasounds performed that thyroid abnormalities are identified. With this concerning trend in mind, it is important to consider possible factors that may affect this important gland and cause inflammation, nodule formation and potential cellular change.

Many substances within our diet and environment can interfere with thyroid function. Collectively, they are called Endocrine Disrupting Chemicals (EDCs). This interference is concerning because our thyroid acts as the control room for our metabolism and also produces important hormones that affect every cell in our body.

EDCs are disruptive to our thyroid because they fit perfectly into our thyroid hormone receptor sites, thereby competing with our thyroid hormones to create a first-in-best-dressed scenario, and changing the information that our receptors are receiving.1,2 Exposure to mixtures of these chemicals, rather than single ones, complicates the matter further. Because EDCs are everywhere (in plastics, cosmetics, fertilisers, insecticides, fire retardants, cleaning products, building materials, processed foods, dust particles, medicines, etc.), we come into contact with them regularly, and in varying combinations.

Due to the way some of these chemicals breakdown (some were designed to break down slowly due to their intended industrial use), chemicals that were banned decades ago are still found in high levels in the environment. They leach into water and soil and as a result, end up in our food chain. Exposure to them occurs through drinking contaminated water, breathing contaminated air, and ingesting contaminated food.1,2

In addition to chemical-based EDCs, there are natural substances that can affect thyroid function, such as foods containing goitrogens. A goitrogen is a substance that interferes with thyroid hormone production or iodine utilisation (iodine is essential for healthy thyroid function). Foods containing goitrogens include brassicas (broccoli, cabbage, cauliflower, mustard greens, Brussel sprouts, kale, kohlrabi, Chinese cabbage and canola oil), radishes, horseradishes, cassava root, soybeans, peanuts, pine nuts and millet.3 The adverse effects of these foods can be avoided by actions such as soaking, washing, boiling and cooking to help in reducing their goitrogenic potency. Ensuring iodine intake is sufficient is also of great importance, as it is a key regulator of thyroid gland function.4

It is clear that the best possible way to protect ourselves from the harmful effects of EDCs is to avoid them, however, as can be seen, some of them are unavoidable as they are in our food and water sources. Avoiding all other contact where possible is the next best course of action, and reassessing your personal care and household cleaning products is the most effective way to begin this process. Eating organic, unprocessed foods will also minimise EDC exposure.

Other factors that are important for thyroid health are ensuring optimal liver health, as a significant amount of the conversion of thyroid hormones occurs here,5 and exercising regularly, as this stimulates thyroid gland secretion and increases tissue sensitivity to thyroid hormone.6

As mentioned, ensuring adequate intake of iodine is essential to maintaining the healthy functioning of our thyroid. Sources of iodine include seafood and sea vegetables, iodised salt, some vegetables (including spinach, garlic, watercress and artichokes), egg yolks, pineapple and citrus fruits.6 The best way to ensure your iodine status is optimal is to measure it via a 24-hour urinary iodine test, in which a specific dosage of iodine is taken, and the level of iodine in the urine is monitored over the following 24 hours.

If you need help with your thyroid or with reducing your family’s exposure to potentially harmful chemicals, contact Naturopath Kathleen McFarlane.


  1. Calsolaro, V., Pasqualetti, G., Niccolai, F., Caraccio, N., Monzani, F. (2017). Thyroid Disrupting Chemicals. International Journal of Molecular Sciences, 18(12): 2583. doi: 10.3390/ijms18122583
  2. Diamanti-Kandarakis, E., Bourguignon, J.P., Giudice, L.C., Hauser, R., Prins, G.S., Soto, A.M., Zoeller, R.T., & Gore, A.C. (2009). Endocrine-Disrupting Chemicals: An Endocrine Society Scientific Statement.
  3. Endocrine Reviews, 30(4): 293–342. doi: 10.1210/er.2009-0002
  4. Pizzorno J, Murray M. (2013). Textbook of natural medicine. Fourth edition. London: Churchill Livingstone Elsevier.
  5. Pierce, S. (2011). Integrative Treatment of Hypothyroidism. Madison, WI: University of Wisconsin Integrative Medicine.
  6. Guild, R. (2017). Know Your Thyroid. Retrieved from
  7. Hechtman, L. (2012). Clinical Naturopathic Medicine. Chatswood, NSW: Elsevier Australia.