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  • Writer's picturejuliakimd

Nutrients needed for optimal thyroid health and function

Many nutrients are needed by the thyroid and the associated enzymes for thyroid hormones to be made, and convert the inactive thyroid hormone (T4) to active thyroid hormone (T3). Numerous studies have found an association between thyroid disorders and nutrient deficiencies.  

Note: Before supplementing with any of the following, you need to do a hair tissue analysis test or blood tests to check your levels – if you supplement when you don’t need to, you can add fuel to the fire. If you would like to do a hair tissue analysis, please get in touch with me. You can download a sample pdf report below:

Hair Tissue Mineral Analysis HTMA Sample Report
Download PDF • 490KB


It's the critical raw material needed to make thyroid hormone and takes up 65% of T4’s molecular weight. Most of the iodine we eat is converted to iodide and well absorbed in the stomach. When the iodide reaches the thyroid, it is bound to thyroglobulin - a protein that's in the thyroid gland - and stored as an iodinated thyroglobulin in the thyroid until more thyroid hormone is required.

During the production of T3 and T4, the hormones combine with the iodinated thyroglobulin, where they take the iodide molecules that were bonded to the thyroglobulin. This leaves the thyroglobulin free to be used again to store iodide to make more hormone. Once T3 and T4 are combined with the iodide, they are released into the circulation, where they bind with other thyroid hormone-specific proteins through the blood stream to target tissues and cells.

Note that the thyroid is not the only part of the body that needs iodine – it's good for the heart, and useful for diabetes, likely as it is antioxidant and anti-inflammatory. It's also good for brain health, and, it seems to be protective against breast cancer, or is it a coincidence that Japanese women have lower incidences of breast cancer compared to other women across the world, possibly due to eating a lot of seaweed and other sea foods, which are a good source of iodine?

A lot of the world is deficient in iodine, since they stopped iodising table salt maybe? All the chronic conditions we have today - heart disease, diabetes, obesity, cancer - they all require a plethora of expensive medications, some evidence suggests all those conditions can be massively helped, or even prevented by supplementing with iodine, and it's far cheaper than the medications! ;)



The thyroid gland contains the highest selenium concentration among all organs in the human body. Absorption of selenium in humans is efficient and not regulated by anything, meaning that selenium deficiency is mainly in regions where selenium soil content is low. There are a few places around the world that have naturally low levels in their soil, however, farmers can add it into their fertilisers - not sure why this is not done as standard!

Selenium plays a significant role in thyroid hormone metabolism as it sits within the structure of thyroid enzymes that convert inactive T4 into its active form, T3. Other thyroid enzymes that contain selenium are involved in deactivating thyroid hormones, serving as a crucial regulatory element in thyroid function.


Where there's a selenium deficiency, there's also a vitamin E deficiency. A selenium deficiency can exacerbate an iodine deficiency, and the same is true for vitamin A or iron deficiency. Note that Selenium, Vitamin A and Vitamin E are all used as antioxidants in the body where to reduce free radicals. Selenium within enzymes also protects the thyroid from free radical damage.


An insufficient selenium status has been associated with adverse mental health outcomes, including symptoms of depressed mood, increased anxiety, and heightened confusion. People who have mercury amalgams or had exposure to mercury and it is stored in tissues, often this can take place of selenium because they are a similar shape to one another. In this case, mercury can be very toxic to the thyroid when it is used instead of selenium.


A study showed that 200mcg Selenium taken every day for 3 months helped lower the thyroid auto-antibodies in autoimmune hypothyroid. One Brazil nut contains approximately 96mcg, so if you eat about 4-6 Brazil nuts (depending on size), this will ensure not only getting fibre but selenium into your diet.  



Although iodine is one of the main components of thyroid hormones, iodine actually requires iron in order for it to be fully utilised. Iron is essential for the human body to synthesise and metabolise thyroid hormones, the body is dependent upon iron to convert T4 into the active T3 via the thyroid enzyme thyroid peroxidase. Randomised controlled intervention trials in iodine- and iron-deficient populations showed that taking iron with iodine resulted in greater improvements in thyroid function and volume than taking iodine alone.  


Incidentally, hypothyroidism can trigger anaemia, and vice versa. The diagram below shows how iron affects thyroid hormones. 

flow chart showing how chronic anaemia affects thyroid hormones



Zinc’s interaction with thyroid hormones is complex – Zinc regulates both the synthesis and mechanism of action of thyroid hormones. Scientific evidence shows that zinc plays a key role in the metabolism of thyroid hormones by regulating thyroid enzyme activity, and the synthesis of thyrotropin releasing hormone and thyroid stimulating hormone (‘TSH’).  

Zinc modulates the structures of essential transcription factors of gene expression that are involved in the synthesis of thyroid hormones. Blood levels of zinc appear to influence the levels of T3, T4 and TSH. Zinc transporter proteins are present in the hypothalamus, pituitary and thyroid, but their functions remain unknown.  

Zinc deficiency is associated with hypothyroidism, especially with hair loss. Thyroid hormones are essential for the absorption of zinc, and hence hypothyroidism can result in acquired zinc deficiency. The hair loss that comes with hypothyroidism may not improve with thyroxine unless zinc supplements are added.



Tyrosine is an essential precursor to both thyroid and adrenal hormones. It is found within thyroglobulin, the protein produced by the thyroid gland which is attached to iodine to create thyroid hormones. When Tyrosine has an iodine molecule attached to it, is becomes one of the iodothyronines, which are precursors for making T4 and T3.  



Vitamin A helps activate thyroid hormone receptors inside the cells throughout the entire body and is another nutrient required by the body to convert T4 to T3. Vitamin A supplementation given alone or in combination with iodised salt can have a beneficial impact on thyroid function and thyroid size.

Low vitamin A levels may reduce thyroid function because the ability to produce thyroid-stimulating hormone (TSH) is limited. An underactive thyroid gland cannot efficiently convert carotene to usable vitamin A, so no matter how many carrots you eat, it won’t help your vitamin A levels.


Vitamin A must be accompanied by protein to make it available to the body, so if you are on a low protein diet, you may be deficient in vitamin A. Vitamin A deficiency impacts thyroid health as it plays a role in the pituitary gland by limiting TSH synthesis and secretion by the pituitary, increasing the size of the thyroid gland, or reducing uptake of iodine by the thyroid gland. Vitamin A has been shown to regulate thyroid hormone metabolism and inhibit TSH secretion via down-regulation of TSH gene expression. 


Vitamin A also helps balance both sides of the immune system, which is our innate immune response (one we’re born with) and the adaptive immune response (one we acquire throughout our life) so it is no surprise that it reduces autoimmune reactions. 



This vitamin is drastically needed if you have an overactive thyroid.  



Thyroid hormone regulates the enzymatic conversion of riboflavin to its active coenzyme forms in adults. Riboflavin is necessary for the development of folate-dependent pathways that may play a role in depression. Lack of vitamin B2 suppresses thyroid function in that the thyroid and adrenal glands fail to secrete their hormones. 



This is needed to keep all the body’s cells (including the endocrine glands) in efficient working order. 



Without this, the thyroid cannot utilise the iodine efficiently to make the hormones. People with an overactive thyroid need Pyridoxine B6 even more, and commonly experience muscle weakness due to the lack in B6. 



Nearly a third of patients with hypothyroidism have a vitamin B12 deficiency. 20-25% of people with autoimmune hypothyroid should also be checked for anti-parietal cell antibodies as standard. Parietal cells are found in the stomach and secrete digestive juices that help break down food so that vitamin B12 is released from the food. When there are anti-parietal cell antibodies in the stomach, it means that these antibodies attack the parietal cells, which leads to less gastric acid secreted, so food is not broken down properly, which leads to low vitamin B12.  



Long-standing vitamin C deficiency causes the thyroid gland to secrete too much hormone. People with an overactive thyroid need extra vitamin C as this is drained from the tissues in their bodies. 



Vitamin D is an immune system modulator, and without enough of it, your immune system is more likely to go rogue and mistakenly attack your own tissues, which is what happens in Hashimoto’s and Graves’ when your immune system attacks your thyroid. Low levels of vitamin D have been associated with higher thyroid antibodies. 

Hypothyroid patients taking vitamin D supplements for 12 weeks improved serum TSH and calcium concentrations compared with the placebo, but it didn’t alter serum T3, T4, ALP, PTH, and albumin levels.  

Some studies report the prevalence of vitamin D insufficiency in Hashimoto's disease (92%) to be significantly higher than in healthy controls (63%), and that the extent of vitamin D deficiency was significantly associated with the degree and severity of hypothyroidism. There are two explanations, one being low levels of vitamin D due to poor absorption via the intestine, or that the body may not activate vitamin D properly. 

It is known that both vitamin D and thyroid hormone bind to similar steroid hormone receptors. Not surprisingly, Vitamin D has been shown to have an important role in oestrogen synthesis in both female and males. TSH levels of middle-aged and elderly women were higher than those of same-age men, indicating that TSH regulation is influenced by sex hormones. Circulating oestrogen acts on the pituitary, which can induce serum TSH suppression in males. Some studies demonstrate that vitamin D modulates pituitary TSH secretion by binding to specific binding sites. Some studies show genetic variations that predispose people to autoimmune thyroid disease suggesting genetic susceptibility or environmental factors may also mediate the relationship between vitamin D status and TSH level. 



Low vitamin E causes the thyroid gland to secrete too much hormone, and too little TSH from the pituitary gland. People with an overactive thyroid need a higher dose of vitamin E to counteract the large amounts of the vitamin depleted from the system.  



Magnesium is required for the conversion of T4 into T3. Stress causes us to lose magnesium at a great rate through urination, and a diet high in refined food, low in vegetables and high intake of caffeine will all encourage urinary magnesium loss. Magnesium is also required for the production of energy so definitely one to take for both hypo- and hyperthyroid. 



Can affect thyroid hormones directly by regulating the deiodinase enzymes that convert T4 to T3. 



Small amounts of copper also needed for thyroid function. 


Toxins that affect thyroid health

Apart from the above nutrients being required for optimal thyroid function, there are several things that have a major impact on the thyroid:

Mercury - unfortunately, this molecule mimics Selenium and is favoured over Selenium but is of course toxic to the thyroid, causing autoimmunity, hypothyroidism, thyroid cancer, and cause oxidative damage and genetic mutations.

Fluoride - drinking fluoridated tap water over time has an effect on the thyroid, albeit that it is in small amounts. It has a slowing effect on thyroid function - one of the reasons to drink filtered water.



The impact of common micronutrient deficiencies on iodine and thyroid metabolism: the evidence from human studies:

Mercury in the human thyroid gland: Potential implications for thyroid cancer, autoimmune thyroiditis, and hypothyroidism:,%2C%20autoimmune%20thyroiditis%2C%20and%20hypothyroidism  

Vitamin B12 levels in thyroid disorders: A systematic review and meta-analysis: 

Hypothesis: dietary iodine intake in the etiology of cardiovascular disease:

Anti-thyroid antibodies, parietal cell antibodies and tissue transglutaminase antibodies in patients with autoimmune thyroid disease:

Selenium treatment in autoimmune thyroiditis: 9-month follow-up with variable doses: 

Zinc Deficiency Associated with Hypothyroidism: An Overlooked Cause of Severe Alopecia:

Severe Iron-Deficiency Anaemia Leading to Hypothyroidism:

Chronic anaemia and thyroid function: 

The effect of vitamin A supplementation on thyroid function in premenopausal women:

Does fluoride exposure affect thyroid function? A systematic review and dose-response meta-analysis:

The Effects of Vitamin D Supplementation on Thyroid Function in Hypothyroid Patients: A Randomized, Double-blind, Placebo-controlled Trial: 

Thyroid Hormone Synthesis And Secretion: 

Effects of Manganese on Thyroid Hormone Homeostasis:  

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