Remember when I said that low thyroid hormones slow down your metabolism? Well, today, we’re deep diving on the topic of hypothyroidism or low thyroid levels, how does what we eat affect our thyroid?

As usual, before we jump into the nutrition side of things, let’s get the low-down on hypothyroidism and the role of the thyroid in the body.

Disclaimer: see your GP if you think (or do) have any issues with your thyroid to get the appropriate testing and medications needed, before seeking dietary advice from an Accredited Practising Dietitian.

What does the thyroid do?

The thyroid gland is located in your neck and produces hormones which are important in numerous metabolic processes, not just your weight, but also body temperature, heart rate and blood pressure (Source: Health Direct).

The thyroid uses iodine (a mineral which we get from food, more on which ones in a sec), to make two main hormones T3 & T4 (they have big long names too, but let’s keep it simple for now, hey?), this process is triggered by another hormone released from your brain called thyroid stimulating hormone (or TSH), there’s also another hormone responsible for releasing TSH, HORMONES ARE COMPLEX, OKAY? What is important for you to know is that every single cell requires thyroid hormones to function!

Hypothyroidism is when not enough thyroid hormone is being produced, this can be due to the body attacking the thyroid cells (autoimmune conditions such as coeliac disease, type 1 diabetes or Hashimoto’s thyroiditis), radiation therapy of the head & neck area, some medications including lithium which is used to treat psychiatric conditions.Almost 5 in 100 people in the US over the age of 12 has hypothryoidism

Symptoms of hypothyroidism include:

  • Fatigue
  • Weight gain
  • Cold intolerance
  • Puffy and pale face
  • Muscle pain
  • Constipation
  • Headache
  • Poor memory or attention span
  • Depression
  • Brittle hair & nails

Some of these can symptoms of numerous conditions (e.g. headache, constipation & fatigue), therefore it is important to get thyroid hormone levels tested by your doctor to know for sure.

People with hypothyroidism generally find weight loss very challenging, particularly without thyroid hormone replacement.

There’s also hyperthyroidism, which is when your thyroid produces too much of the hormones which can cause a different array of symptoms such as nervousness, heat intolerance, tiredness, weight loss and heart palpitations (Source: Health Direct)

Hypothyroidism & Fertility

Remember how I said that low thyroid hormones affect EVERY cell in your body? Well this (unfortunately) includes your reproductive system, ladies! Low thyroid hormones can prevent egg release and therefore no ovulation, issues with implantation due to the short second half of the menstrual cycle, high prolactin levels due to the upstream thyroid releasing hormones accumulating creating irregular or anovulation.

Women who struggle with infertility have a higher prevalence of hypothyroidism of about 24% compared to the general population. With a study showing that treatment of the condition with oral medication found that more than 75% of women conceived within 6 weeks to 1 year! (Source: Verma et al., 2012)

Need I say again, go get yourself tested!

So, onto the nutrition component, what nutrients are an actual concern or have been thought to be useful in thyroid health?


Well, if you’ve read the little medical intro up there, you would know that the thyroid is responsible for absorbing iodine and is an essential component of the thyroid hormones, T3 & T4.

The average adult needs 150 micrograms (mcg) per day of iodine (Source: NRVs).

In Australia, key sources of iodine in the diet include (Source: FSANZ):

  • Iodised salt
  • Bread made with iodised salt, except organic breads (2 slices = 28 mcg)
  • Seafood (especially oysters! 6 oysters gives you 100% of your daily iodine needs)
  • Canned salmon (1 small tin = 63 mcg)
  • Seaweed (Kombu Kelp has the highest concentration, wakame followed by nori)
  • Sushi (containing seaweed) (1 roll = 92 mcg)
  • Eggs (2 eggs = 19 mcg)
  • Prunes (5 prunes = 13 mcg)

Dairy foods can be a source of iodine due to the solutions used to disinfect the milking equipment, however this may vary from farm to farm, and is generally not listed on the nutrition information panel.

Since iodine fortification was introduced in 2009 in Australia, the number of adults meeting iodine recommendations increased, especially in the target group which was women of child-bearing age (Source: FSANZ).

Countries without access to seafood and without iodine fortification programs are more likely to be at risk of iodine deficiency.

Seafood and Iodine

Iodine deficiency isn’t too common here in Australia, but iodine deficiency is a potential cause of hypothyroidism, with extreme nutrient deficiencies causing goitre, or the swelling of the thyroid gland which when it becomes more severe can be visible externally.

Iodine deficiency during early pregnancy and throughout has been shown to reduce your baby’s IQ and skills in key learning areas such as reading, writing & spelling. In severe circumstances (again very rare in the Western world), it can cause cretinism or mental retardation. Most pre-natal vitamins contain iodine, plus you can get some from what you eat!


Selenium is another mineral which is found mostly in the thyroid tissue. It is responsible for the formation of antioxidants and thyroid hormone metabolism.

Research suggests that selenium supplementation with patients with autoimmune thyroiditis (like Hashimoto’s) is associated with improved thyroid function (Ventura et al., 2017). A similar effect is seen in mild Graves’ disease (a type of immune-related hyperthyroidism) The recommended form of selenium supplementation is the organic form, you should always consult your health care professional before starting any kind of supplement. There is limited information about recommended dosages available.

One review Kohrle (2015) stated that it’s not just selenium that is required but also sufficient iodine and iron required for a healthy and functioning thyroid gland.

Find out more about increasing your iron intake.

The recommended intake for Selenium is 60 micrograms per day for adult women and 70 micrograms per day for adult men (Source: NRVs).

So where can you find selenium in food? Well, selenium content in food is really determined by geography as it enters the food supply via the soil, some of the top dietary sources of selenium are (Source: NIH):

  • Brazil nuts (just 1 nut = 100% of your daily needs)
  • Tuna
  • Beef
  • Turkey
  • Chicken
  • Cottage cheese
  • Eggs
  • Brown rice
Tuna Fish

True selenium deficiency is known as Keshan Disease which can result in heart conditions and is prevalent in parts of Asia & Africa. What is more relevant in Australia is less than ideal selenium intake which can result in thyroid disorders, immune dysfunction, inflammatory conditions & even male infertility. Fun fact, an excess of selenium may result in “garlic breath”

Soy Foods

With more and more people turning away from animal sources of protein and their by-products, the consumption of soy is definitely on the rise. But, many people fear that the phytoestrogen (a bioactive plant chemical that mimics the function of estrogen) found in soy are interfering with their hormones, particularly the sex hormones (estrogen & testosterone).

Edamame Beans, Soy Foods and Thyroid Health

A review of the literature done by Messina & Redmond (2006) showed that there were no effect or very modest changes in thyroid function parameters across 14 trials. Further to this, in people with normal thyroid function and had sufficient iodine intake, soy foods and isoflavones (the component in question) did not negatively affect thyroid function. The authors stated that even hypothyroid patients need not avoid soy foods, it may be an issue if your iodine intake is poor.

Still worried? For a great run-down of the soy evidence here.

Cauliflower, Kale & Broccoli

These veggies are in question due to the presence of goitrogens. As the name suggests sounds like it may have something to do with goitre, if you’re eating normal sized servings there’s nothing to be concerned about. These veggies are incredibly nutritious and shouldn’t be avoided!

Kale and Thyroid Health

If you’re really concerned, make sure they’re boiled before eating to reduce the content of the compound that MAY interfere with your thyroid hormones.


Should be completely avoided in the case of confirmed coeliac disease. People with coeliac disease (an autoimmune autoinflammatory condition) are more likely to have antibodies that attack their thyroid cells reducing the thyroid hormones produced resulting in hypothyroidism. Whilst there’s no cure, complete gluten exclusion for life is required for coeliac management.

Coeliac Disease and Thyroid Health

Find out the difference between coeliac disease & gluten intolerance here.

Take care of your thyroid, get tested and seek help with your diet to help you manage your condition! If you’re looking for a dietitian who understands hypothyroidism, then please get in touch for a face-to-face or virtual consultation.

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