How nutrition may influence thyroid health

As with many chronic conditions, the information about what you should eat with hypothyroidism is often confusing and conflicting. So let’s clear a few things up!

Firstly, what is hypothyroidism?

Hypothyroidism is just a fancy word to describe an underactive thyroid. Your thyroid is a gland in your neck that produces two hormones: triiodothyronine (also known as T3) and thyroxine (also known as T4). The primary roles of T3 and T4 are to regulate metabolism, growth and development. When the thyroid is underactive, many of the body’s functions begin to slow down

Symptoms of hypothyroidism include:

• Fatigue
• Weight gain or difficulty losing weight
• Dry hair and skin
• Sensitivity to cold temperatures
• Muscle cramps, aches and weakness
• Mood disturbances
• Abnormal menstrual cycles or infertility

If left untreated, these symptoms will worsen over time, so it’s important to consult with your primary health provider if you’re worried about your thyroid function.

What causes hypothyroidism?

There are two major causes of hypothyroidism.

Firstly, inflammation of the thyroid gland, known as thyroiditis, can damage the cells of the thyroid and leave them unable to produce sufficient (or any) T3 and T4 hormones.

Secondly, there are a multitude of medical interventions that can hinder thyroid function. These include removal of part or all of the thyroid gland, radiation therapy for cancer and certain medications.

So how can I cure hypothyroidism through my diet?

The short answer: you can’t!

We hope the title of this article brought out your inner sceptic! While we’re obviously passionate about nutrition and its influence on health (after all, dietitians are experts in nutritional science!), we want you to be critical – when something sounds too good to be true, it probably is! In other words, if someone is promising to cure your chronic illness with food, take it with a grain of salt (pun intended!)

This being said, in conjunction with medical management, your diet can absolutely help to optimise thyroid function and manage the symptoms of hypothyroidism.

Your dietary requirements for thyroid health really depend on whether or not you have been prescribed medication for your hypothyroidism. The most common medication for an underactive thyroid is levothyroxine, an artificial version of the T4 hormone. However, some of the nutrients that are typically beneficial for thyroid health actually inhibit the function of levothyroxine and should therefore be avoided by some people with hypothyroidism.

If you have hypothyroidism, the nutrients you should be mindful of include:

Iodine

Iodine is essential for the production of T3 and T4. In fact, T3 is created by the body by removing a single atom of iodine from a T4 molecule. Both too much and too little iodine is harmful to thyroid function, so make sure you ask your doctor to check your levels if you’re concerned.

Iodine deficiency has become less common in many developed countries due to the fortification of foods like salt and bread with iodine. However, the UK is one of only 12 countries in Europe with no legislation around iodine fortification, so you’ll need to focus on foods that are naturally rich in this nutrient, such as tuna, eggs and dairy products. This factsheet from the British Dietetic Association can tell you everything you need to know about iodine. 

If you’ve been prescribed levothyroxine, your thyroid function is likely severely impaired and consequently, your ability to absorb iodine is compromised; therefore, over-consumption of iodine can be dangerous and even make hypothyroidism worse! Be sure to consult with your doctor before taking any supplements or eating seaweed (which is extremely high in iodine).

Selenium and zinc

These two minerals are essential for thyroid function, as they help to convert T4 into T3.¹ This is key to optimising the effectiveness of levothyroxine, as this synthetic form of T4 must be converted into T3 by the body in order to maintain muscle control and the function of the brain, heart and digestive system. Foods rich in selenium include brazil nuts, tuna, sardines and turkey, while zinc can be found in oysters, beef, pumpkin seeds, cashews and chickpeas.

Caffeine, calcium, fibre and soy

Research has shown caffeine to hinder the absorption of levothyroxine, lowering its effectiveness.² Wait at least 30 minutes after taking your medication before pouring your morning tea or coffee, and then you’ll be good to go!

Calcium and fibre have a similar effect on levothyroxine; however, they are vital for optimal health, so be sure not to avoid them!³ Calcium is key for maintaining bone strength and density, and is found in dairy products and leafy green vegetables, as well as fortified foods like almond and rice milk. Fibre is vital for good gut health and heart health, and is primarily found in grains and the skins of fruit and vegetables. Fibre is particularly important for people with hypothyroidism, as they have an increased risk of heart disease.⁴ The current recommendation is that a period of four hours should be left between taking your medication and consuming calcium- or fibre-rich foods.

Soy also appears to interfere with levothyroxine absorption, although the function is not completely understood.⁵ Again, waiting four hours between taking your medication and the consumption of soy products like soy milk, tofu and edamame can help circumvent this issue.

If you are seeking one-on-one support relating to eating for hypothyroidism, reach out to our expert dietitians at [email protected]. We would love to help!

Karli Battaglia MDiet, APD

EHL Team x

References

1. Ventura M, Melo M, Carrilho F. Selenium and Thyroid Disease: From Pathophysiology to Treatment. International Journal of Endocrinology. 2017;2017:1-9. 
2. Benvenga S, Bartolone L, Pappalardo M, Russo A, Lapa D, Giorgianni G et al. Altered Intestinal Absorption of L-Thyroxine Caused by Coffee. Thyroid. 2008;18(3):293-301. 
3. Chon D, Reisman T, Weinreb J, Hershman J, Leung A. Concurrent Milk Ingestion Decreases Absorption of Levothyroxine. Thyroid. 2018;28(4):454-457. 
4. Klein I, Danzi S. Thyroid Disease and the Heart. Circulation. 2007;116(15):1725-1735. 
5. Fruzza A, Demeterco-Berggren C, Jones K. Unawareness of the Effects of Soy Intake on the Management of Congenital Hypothyroidism. PEDIATRICS. 2012;130(3):e699-e702.