Overview

If you're living with hypothyroidism, you’ll know first-hand how its long list of possible symptoms can impact your well-being. But did you know that your diet can play a significant role in managing these symptoms? 

By incorporating iodine, selenium and fibre-rich food sources into your diet, moderating your intake of goitrogenic and highly-processed foods and timing your medication right, small changes to your eating habits can have protective effects on the bodily systems governing your thyroid hormones.

Whether you're newly diagnosed or looking to better manage your symptoms, understanding the connection between hypothyroidism and diet can help you feel better equipped to take control of your health.

Understanding hypothyroidism

The thyroid gland is a small, butterfly-shaped gland that sits inside the base of your neck. In keeping with its name, its main function is to produce and store thyroid hormones, which play a number of important roles in our body, including growth, development and metabolism.

Therefore, people who lack sufficient thyroid hormones due to hypothyroidism (‘hypo’ meaning low) may experience a range of symptoms including fatigue, constipation, weight gain, hair loss, depression and high cholesterol (hypercholesterolaemia), among many others.¹ 

Two main types of hypothyroidism exist depending on the underlying cause, including:

• Primary hypothyroidism: This accounts for the vast majority of people with hypothyroidism and results from the problems with the thyroid gland² 
• Central hypothyroidism: Thyroid stimulating hormone (TSH) stimulates the production of thyroid hormones from the thyroid gland. Insufficient TSH can therefore result in hypothyroidism, of which there are two types that may occur alone or together:
  • Secondary – issues with the gland that makes our TSH (the pituitary gland)
  • Tertiary – involving the hypothalamus, an area of your brain that manages the production and release of hormones (working closely with the pituitary gland)³

Restoring thyroid hormone levels back to a healthy range via hormone replacement medications (e.g. levothyroxine) is the main way of managing hypothyroidism. However, some people may still experience symptoms even while taking these medications.² Fortunately, lifestyle choices such as your diet may, alongside medication, help to manage these symptoms by promoting healthy body weight and potentially protecting and/or improving the functioning of your thyroid, pituitary gland and hypothalamus.⁴  

Foods to eat

Iodine-rich foods

Iodine is essential for thyroid hormone synthesis. In fact, iodine deficiency is the most common cause of hypothyroidism across the globe.² It’s worth noting that the recommended daily allowance (RDA) for iodine is 150 micrograms/ day for adults. 

Examples of iodine rich-foods include:

• Iodised salt
• Seafood (e.g. fish, shellfish)
• Seaweed (e.g. kelp, nori, kombu, wakame)
• Dairy products
• Eggs 

If you're thinking of securing your iodine fix via supplements, be sure to check with your doctor first; iodine deficiency is rare in more economically developed countries and unnecessary supplementation may worsen your condition - unless your hypothyroidism is caused by iodine deficiency.

Selenium sources

Another supplement is selenium, which is a major component of selenoproteins - a group of proteins that aid in thyroid hormone metabolism and protect the thyroid gland from oxidative stress. They do this by regulating the reactions involved in thyroid hormone production and neutralising cell-damaging chemicals called free-radicals that are released during this process.⁵ 

Incorporate some of the selenium-rich foods listed below into your diet to bolster your thyroid health:⁶ 

• Brazil nuts
• Seafood (especially tuna, yellowfin, sardines and shrimp)
• Meat and poultry (e.g. beef, ham, turkey, chicken) 
• Cereals, bread and other grains
• Baked beans
• Oatmeal
• Eggs
• Dairy products (e.g. cottage cheese, milk, yoghurt)

Brazil nuts in particular are a great option, boasting around 544 micrograms of selenium per serving (6 to 8 nuts); throwing in just 2 brazil nuts into your snacking regime is a simple and convenient way to meet your daily needs - especially if animal products aren’t your thing.

It’s important to follow the RDA of 55 micrograms/ day if you’re an adult over the age of 19, as exceeding the upper limit of 400 micrograms/ day can lead to toxicity, although this condition (known as selenosis) is rare.⁵ 

Fibre-rich foods

Fibre may help to relieve constipation and facilitate the maintenance of healthy weight. Getting plenty of fibre is also associated with a lower risk of type 2 diabetes and heart disease. Given the association between hypothyroidism, obesity and the development of these related diseases, incorporating fibre into your diet is a great way to improve satiety, aid digestion and manage weight effectively.⁷

The best sources of fibre come pre-packaged by nature in the form of fruits and vegetables; not only are they abundant in fibre, but also provide powerful antioxidants such as polyphenols. These compounds have been linked with an array of health benefits, owing to their ability to fight oxidative stress and inflammation - key players in the onset and development of many diseases. This includes reducing inflammation of the hypothalamus which, when persistent, can also lead to the development of obesity.⁸ 

It’s recommended that adults get around 30 grams of fibre per day. Regularly incorporate the following fibre-rich foods into your diet to help achieve this daily target:

• Fruits (especially berries)
• Vegetables (especially leafy greens)
• Whole grains (such as oats, quinoa, and brown rice)
• Nuts
• Seeds
• Beans
• Pulses

Foods to avoid 

Goitrogenic foods

Goitrogens are compounds that can, in large amounts, interfere with thyroid function by inhibiting hormone synthesis. ⁹ To reduce a food’s goitrogenic activity while still reaping their health benefits, consider cooking them before eating. 

Examples of goitrogenic foods include: ⁹ 

• Raw cruciferous vegetables (e.g., cabbage, kale, broccoli, bok choy and Brussels sprouts)
• Starchy plants (e.g. turnip and some forms of root cassava)
• Pearl millet
• Soy products

Excessive soy consumption

Soy contains compounds known as isoflavones which have previously been shown to interfere with thyroid hormone absorption and synthesis, leading to concerns about the potential impact of soy consumption on thyroid health. However, research suggests that soy isoflavones have no effect on thyroid hormones, and only mildly raise TSH levels (thyroid hormones suppress TSH release, so low levels of thyroid hormones means higher TSH levels - an indicator of hypothyroidism). ¹⁰ 

Examples of foods with a high soy content include:

• Soy milk
• Tofu
• Tempeh
• Miso
• Edamame

Mirroring the health advice surrounding goitrogens, soy doesn’t need to be completely avoided. However, the Mayo clinic recommends the following in line the directions typically given alongside levothyroxine: 

• Take medication on an empty stomach, ideally at the same time everyday, e.g. first thing in the morning
• Avoid eating, drinking or taking other supplements or medications for an hour after taking your dose
• Wait until 3 to 4 hours after meals to take your medication 

These guidelines apply whether or not the food or drinks contain soy. It’s always best to speak with your doctor to find out what works for you and the type of medication you’re taking. 

Highly-processed foods and drinks

Highly-processed foods often include refined sugars and saturated fats, which can both exacerbate thyroid dysfunction and contribute to weight gain. Considering the link between hypothyroidism and obesity, which itself is associated with the development of various chronic diseases, prioritising whole, nutrient-dense foods is imperative to supporting overall health and thyroid function.^7,8

Although not all processed food is bad for you, it’s well-advised to minimise your consumption of the highly-processed variety where possible by swapping them out for healthier alternatives. Some common examples of highly processed foods and drinks are:

• Sugary snacks
• Breakfast cereals
• Packaged snacks
• Fast food and ready meals
• Refined grains (e.g. white flour, white bread and white rice)
• Processed meats (e.g. ham, bacon, sausages and salami)
• Carbonated drinks
• Some alcoholic drinks (e.g. whiskey, gin and rum)

Lifestyle tips for managing hypothyroidism through your diet

Portion control and balanced meals

There’s no single perfect meal plan for hypothyroidism; to get the most benefit out of what you eat, practice portion control and aim for balanced meals that incorporate protein, fibre, healthy fats, and complex carbohydrates to regulate metabolism and promote healthy weight management.

Everyone’s experience with hypothyroidism is unique, so it's best to create a personalised eating plan tailored to your individual health requirements. If possible, consider collaborating with a registered dietitian who can identify any foods you may need to exclude while ensuring your diet remains well-balanced, retaining essential nutrients without unnecessary restrictions.

Regular monitoring and adjustments

It’s crucial to remain proactive about monitoring your thyroid function through regular tests and working closely with your doctor to adjust your diet and medication as needed. This is particularly true if you’re planning on making significant dietary changes, or are struggling to manage your symptoms while on medication.

Taking supplements 

Nutrient deficiencies may worsen some of the symptoms of hypothyroidism, particularly fatigue and low mood. It's worth discussing with a healthcare professional the incorporation of vitamin and mineral supplements to address any identified deficiencies that you’re struggling to obtain through natural dietary sources.¹¹ 

Importantly, taking supplements excessively or unnecessarily can have adverse effects, potentially affecting thyroid function and the absorption of your medication (especially calcium and iron). Therefore, any significant changes to your diet should be done under the supervision and guidance of your doctor.

Summary

A balanced diet tailored to support thyroid function can be an invaluable tool for both alleviating symptoms of hypothyroidism and boosting your overall health. Simple, actionable changes include the addition of iodine, selenium and fibre-rich foods to your daily diet, while avoiding the excessive consumption of goitrogenic and highly-processed options wherever you can. 

Alongside lifestyle practices such as portion control, meal planning and regularly monitoring thyroid function, these choices can empower you to optimally manage your condition under the guidance of healthcare professionals.