Thursday 24 May 2018

In thyroid patients, there is still a long way to go in terms of goitrogens. These are substances that prevent the absorption of iodine into the thyroid gland. But which goitrogens should we actually worry about? And which substances ultimately have a beneficial effect?


Part 4: nutritional treatment

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On internet forums thyroid patients have wide-ranging discussions about goitrogens. These are substances that prevent the absorption of iodine into the thyroid gland. Because of that, the hypophysis starts to produce extra TSH, resulting in the thyroid gland increasing in size: this is known as a goitre or struma.

Most discussions are about thiocyanates that occur naturally in brassicas (for example, kale and sprouts) and isoflavones that occur in soya beans, etc. Cassava also contains the goitrogenic agent cyanide. Generally, plants only contain small amounts of goitrogens. Cooking and soaking removes the majority of goitrogens. To the contrary, processing and refinement can increase the level of goitrogens, for example, when processing rapeseed into rapeseed oil and oils of other cruciferous vegetables. Rapeseed oil can be found in many ready-made products. 

Fermentation can also have an effect on the level; for example, in sauerkraut in the first couple of hours, the majority of the thyroid-inhibiting substances are disrupted. After two weeks (at the latest) the goitrogen levels are much lower [11].

Avoid or not?

Human studies did not demonstrate changes in thyroid homeostasis in relation to the consumption of cabbage, soya or cassava [1]. This may be because, in normal consumption, no problems occur, or because during the study raw foods are not used (particularly not raw cassava, which contains hydrocyanic acid). In studies in the 1950s involving rabbits– who ate raw cabbage– an effect on the thyroid gland was found [10]. It is also known that daily consumption of certain types of millet causes problems with thyroid homeostasis [12]. Some people eat millet as a replacement for bread, which in this light is imprudent.
A cautious conclusion is that it is not immediately necessary to totally avoid these food sources, although that is more difficult with rapeseed oil. But it is important that cruciferous vegetables are cooked and not eaten raw every day. Eating excessive amounts of raw cabbage is advised against anyway, particularly if someone has an iodine deficiency.



Within nutritional practice– in addition to lifestyle advice– there are a number of supplements that support thyroid function. 



A lack of this element can cause hypothyroidism and sufficient iodine is therefore also crucial for producing sufficient thyroid hormone. Iodised salt is available and this is added to the majority of bread. However, Dutch people are eating less bread, which means that more seaweed (for example) should be consumed or iodine should be supplemented.

In terms of gluten and thyroid gland disorders, people who suffer from one auto-immune illness, such as type 1 diabetes or Coeliac disease (gluten intolerance), are at an increased risk of developing a second auto-immune illness, such as Hashimoto’s disease or Graves’ disease. Especially Coeliac disease and Hashimoto’s disease often occur simultaneously. There are various explanations for that: it is possible that the damage to the internal wall in Coeliac disease interferes with absorption of essential nutrients for the thyroid gland, such as selenium. It is possible that the antibody involved in Coeliac disease also affects the thyroid gland and it may be the case that both illnesses actually form one syndrome, affecting several organs. Patients who suffer from Hashimoto’s disease should then possibly also be screened for Coeliac disease (and vice versa) [3]. Studies suggest that people with Hashimoto’s disease – whether or not they have Coeliac disease – may benefit from a gluten-free diet [3]. 

That does not mean that a gluten-free diet is a way of treating or preventing all thyroid symptoms. The risk of a gluten-free diet is an iodine deficiency (because they would then no longer be consuming iodine). And that in turn can cause struma and cretinism. Therefore, if someone follows a gluten-free diet, supplementation may be advisable [3].

If someone also suffers from Hashimoto’s disease, then iodine supplementation isn’t a good idea. The symptoms can worsen because an excess of iodine can suppress the production of thyroid hormone. This is called the Wolff-Chaikoff effect, named after the people that discovered it [3].Vice versa, in Graves’ disease, iodine can be used to suppress the production of thyroid hormone and, provided that the patient is monitored carefully, that can then be a useful supplement. In the past, this was the treatment of first choice, before the anti-thyroid hormone medicines propylthiouracil and methimazole were discovered. 

The acceptable daily intake for iodine for adults is 150 micrograms a day; for pregnant and breastfeeding women, this is (temporarily) 250 micrograms a day. Important sources are seafood (fish, seaweed, shellfish and crustaceans), animal products, cranberries and strawberries [3].



Selenium is a building block of a number of important enzymes in our body (selenoproteins). They are unable to function correctly without the presence of this mineral. Such selenoproteins are also involved in the conversion of T4 to T3 in the body. People who have a selenium deficiency have an elevated T4 and an elevated T4:T3 ratio, whilst their TSH is normal. Numerous studies demonstrate that selenium supplementation helps to alleviate the symptoms in Hashimoto’s disease: particularly the inflammatory and immune responses [3].

The chance of someone having a selenium deficiency has shown an upward trend recently. The agricultural land where our food is grown is relatively depleted of selenium. Because of that, the level of this essential mineral is gradually decreasing in plant and animal-based food. Through climate change, this problem will be exacerbated further still, because excess rainfall will flush selenium out of the soil. In the Netherlands, the average selenium intake is estimated to be 40 micrograms a day [4]. The acceptable daily intake for selenium is at least 50 to 150 micrograms a day, but some experts think that 200 micrograms a day is optimal. More than half of men and women consume too little selenium [4].One way of supplementing low consumption is the use of a supplement. Organic selenium yeast is absorbed readily. Eating 1 or 2 Brazil nuts a day can also fulfil the need for selenium. Other sources of selenium are oysters, tuna, wholemeal bread, sunflower seeds, meat, rye and mushrooms [3].



People also tend to eat too little of another mineral - zinc. Zinc also plays a role in thyroid gland function. A small-scale study revealed that low zinc levels appeared to go hand-in-hand with low blood levels of the thyroid hormone. Supplementation with zinc sulphate resulted in an increase in the thyroid hormones and improved efficiency (conversion from T4 to T3) [5, 6].


Vitamin A and retinoids 

In the thyroid gland, retinoids influence iodine homeostasis. A vitamin A deficiency intensifies thyroid gland problems and worsens thyroid gland disorders that result from an iodine deficiency, such as goitre [7]. 


Vitamin D

Vitamin D is increasingly being seen as a hormone, or in any case, as a vitamin with a hormonal function. Certain genetic variations in vitamin D metabolism are correlated with the incidence of auto-immune illnesses. The thyroid gland has receptors for vitamin D, which means that vitamin D influences thyroid gland function. However, little is known about the link between the vitamin D status and thyroid gland function. We do know that vitamin D is crucial for the immune system. Vitamin D therefore possibly deserves a role in supporting the treatment, particularly when there is a low vitamin D status [8].



The amino acid tyrosine forms the structure of the thyroid hormone thyroxine. It is also the raw material for the production of dopamine, adrenaline and noradrenaline. It is also used to produce melanin, the pigment responsible for hair and skin colour. Around 4 percent of all proteins consist of tyrosine [9]. In addition, the body can convert the essential amino acid phenylalanine into tyrosine. A lack of tyrosine can be the result of genetic disorders (such as phenylketonuria). In those cases, supplementation with tyrosine is essential. People who are under a lot of stress, have a busy life or who have a high chemical burden have a greater requirement for Tyrosine [13, 14, 15].



As mentioned above, the thyroid gland is an exceptionally relevant and interesting organ which we can put to good use in nutritional practice, both in terms of diet and supplementation, but also exercise and other lifestyle interventions. Provided they can be correctly interpreted and it is understood where the limitations are, blood levels provide a good insight. Ultimately, everybody has unique levels within the HPT axis which, without further investigation, cannot be regarded as objectively healthy or unhealthy.
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3. Liontiris MI, Mazokopakis EE. A concise review of Hashimoto thyroiditis (HT) and the importance of iodine, selenium, vitamin D and gluten on the autoimmunity and dietary management of HT patients. Points that need more investigation. Hell J Nucl Med. 2017 Jan-Apr;20(1):51-56. 

4. Loon JW van , Ooik A van , Ritsema R, 24-hours total diet study 1994 - intake of selenium, RIVM Report 515004002, 30-06-1996

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6. Ambooken B, Binitha MP, Sarita S, Zinc Deficiency Associated with Hypothyroidism: An Overlooked Cause of Severe Alopecia, Int J Trichology. 2013 Jan-Mar; 5(1): 40–42.

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8. Nettore IC, Albano L, Ungaro P et al,  Sunshine vitamin and thyroid, Rev Endocr Metab Disord. 2017; 18(3): 347–354.

9. USDA's National Nutrient Database for Standard Reference, 23rd edition

10. Steinegger, E., Hänsel R., Lehrbuch der allgemeinen Pharmakognosie, D. 549, Springer, Berlin/Heidelberg/New York (1963)

11.  Tolonen M, Taipale M, Viander B, Pihlava JM, Korhonen H, Ryhänen EL., Plant-derived biomolecules in fermented cabbage, J Agric Food Chem. 2002 Nov 6;50(23):6798-803.


13. Food and Nutrition Board, Institute of Medicine. The Role of Protein and Amino Acids in Sustaining and Enhancing Performance. Washington, DC: National Academy Press, 1999. Available at:

14. Rasmussen, D. D., Ishizuka, B., Quigley, M. E., and Yen, S. S. Effects of tyrosine and tryptophan ingestion on plasma catecholamine and 3,4-dihydroxyphenylacetic acid concentrations. J.Clin.Endocrinol.Metab 1983;57(4):760-763.

15. Reinstein, D. K., Lehnert, H., and Wurtman, R. J. Dietary tyrosine suppresses the rise in plasma corticosterone following acute stress in rats. Life Sci. 12-9-1985;37(23):2157-2163.