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What to eat for underactive thyroid gland

Best diet for hypothyroidism: Foods to eat, foods to avoid.


Best diet for hypothyroidism: Foods to eat, foods to avoid

What is hypothyroidism?

Hypothyroidism (underactive thyroid) is the most common type of thyroid disease and occurs when the thyroid is not producing enough thyroxine (T4).

This can happen as a result of a malfunctioning pituitary gland that is not sending enough Thyroid Stimulating Hormone (TSH) to your thyroid, or your TSH levels are normal, but your thyroid isn’t producing enough T4 and T3 to adequately fuel your cells. To check these levels it is often best to have a thyroid test.

Signs and symptoms include tiredness, low mood, dry skin, thinning hair, sensitivity to the cold, constipation, low libido, menstrual disturbance, weight gain, low mood and difficulty concentrating.

How does hypothyroidism affect your metabolism?

In Functional Medicine, we pay close attention to the thyroid because of its far-reaching impact on overall health. The thyroid regulates the body’s metabolism by influencing how quickly you produce energy from nutrients and oxygen. For example, if you have an underactive thyroid, you won’t be able to optimally regulate your blood sugar, cholesterol, or weight. The thyroid also acts somewhat like a thermometer by regulating body temperature as well as other important functions such as heart rate, brain development, the reproductive system, and bone maintenance.

Thyroid hormone function has a profound impact on overall health via:

  • Modulation of carbohydrate, protein, and fat metabolism
  • Vitamin utilization
  • Mitochondrial function
  • Digestive process
  • Muscle and nerve activity
  • Blood flow
  • Oxygen utilization
  • Hormone secretion

How does diet affect hypothyroidism?

The thyroid gland is extremely sensitive to any change and imbalance, so we must consider a system-wide approach when looking at putting a treatment plan together. The cause and symptoms of hypothyroidism will be different for each individual, there is certainly no ‘one size fits all’ when it comes to this multifactorial condition. This is where
functional medicine offers a much more thorough and comprehensive approach to this complex condition.

There are many aspects of health we need to consider when looking at dietary recommendations for our patients:

  • Stress and adrenal function
  • Gut health and immunity [1]
  • History of viral or bacterial infection [2]
  • Gluten sensitivity
  • Environmental toxicity [3]
  • Nutrient deficiency [4] [5]

Find out more about these key factors on your Thyroid treatment page.

When creating a personalised dietary plan, we also need to consider some of the chronic conditions that are related to hypothyroidism – whether its cause or affect:

  1. Obesity
  2. Diabetes
  3. Cardiovascular disease and high cholesterol
  4. Depression
  5. Autoimmune disease – especially if Hashimoto’s is the main trigger of your thyroid condition

How to increase thyroid hormone naturally

Many of our patients present with symptoms that suggest potential thyroid problems. Our experienced practitioners approach these cases using the functional medicine framework to create a personalised dietary and lifestyle plan.

From functional testing, through identifying nutrient deficiency to lifestyle suggestions, our clinicians will outline their treatment plan and provide guidance on how to improve your thyroid health naturally. We often find that we need to consider many aspects of health outside of the thyroid, all of which may be contributing to our patients’ symptoms.

Here are the key steps to determine the root cause of the symptoms:

  • Taking the full history of our patient to identify what triggered the symptoms initially.
  • Food diary to help us evaluate key nutrient deficiencies linked to poor thyroid function.
  • Laboratory tests to evaluate thyroid function as well gut health, immune activation, toxicity, and stress levels.
  • Discuss environmental and lifestyle factors that support the thyroid.

Which nutrients are important?


Iodine is a trace element needed to stimulate the production of thyroid hormone (T4) and supports the conversion of T4 to T3 (the active form), so getting enough in the diet is important. While iodine deficiency is the most common cause of hypothyroidism, in rare cases, too much iodine supplementation may cause harm. This is why iodine is a controversial nutrient when it comes to thyroid health and a balance is needed to support optimal health. It is important to note, that iodine supplementation will impact the thyroid most significantly in the presence of selenium deficiency [6].

Best dietary sources: seaweed, eggs, saltwater fish, and shellfish.


Selenium is an essential trace element needed for the proper conversion of T4 (inactive thyroid hormone) to T3 (active thyroid hormone). Selenium is also a precursor to one of the most important antioxidants in the body and may help reduce inflammation that can specifically impact the function of the thyroid. While severe deficiency is rare, suboptimal levels may impact thyroid function [7].

Best sources: Brazil nuts (they are very concentrated in selenium, so most people only need 1-3 nuts most days to meet their needs), shrimp, halibut, sardines, grass-fed beef, salmon and turkey.


Zinc is an essential trace element that plays an important role in thyroid health by converting T4 to T3 and in the production of TSH.

Best sources: shellfish, beef and other red meats, legumes, kidney beans, pumpkin seeds, almonds and cashew nuts.

At the London Clinic of Nutrition, we may use nutritional testing, to get a better refinement of exactly which nutrients may be imbalanced. Whether it is related to B vitamins, minerals, antioxidants, omega 3 fats, nutritional testing is particularly useful for our clinicians to evaluate thyroid specific nutrients but also allows us to take a broader approach to our patients’ overall nutritional needs.

Which nutrients are harmful?


Goitrogens are plant compounds that may interfere with the normal functions of the thyroid gland. Certain goitrogens, called glucosinolates, may reduce iodine from getting into the cells of the thyroid, interfere with the production of TPO (which is needed to make T4), and reduce TSH. Scientific evidence on goitrogen avoidance is still mixed, however the general guidance is to reduce these compounds in the diet, particularly in iodine deficient populations. Another important tip is to make sure to cook them as it reduces goitrogen levels in these plant foods [8].


Soy isoflavones inhibit the enzyme thyroid peroxidase (TPO) that plays a key role in thyroid hormone synthesis, and they also interfere with thyroid hormone production. Soy has also been shown to elevate TSH in women, so it’s best to avoid soy products, especially if you already have a documented thyroid imbalance [9].


Many of our patients with thyroid disease have some type of gut dysbiosis or leaky gut. This enables gluten to enter the bloodstream via the “leaky” walls of the gastrointestinal tract. When this happens, the immune system launches an attack, and your thyroid tissues can get caught up in the crossfire. Unfortunately, your thyroid is at risk for rogue autoimmune attacks because gluten closely resembles that of thyroid tissue. In many cases, staying gluten free is the best option but we sometimes find that once gut dysbiosis and leaky gut are addressed, patients can go back to consuming small amounts of gluten such as fermented sourdough [10].

Processed foods

Processed foods and sugars create hormonal imbalances, increase inflammation, and prevent gut and thyroid healing and recovery, so all processed foods should be avoided when someone has thyroid disease.

Other dietary tips

  • Include pre and probiotic foods to address dysbiosis [11]
  • Have a plant-based diet that is high in colourful phytonutrients from fruits and vegetables to provide antioxidants and anti-inflammatory compounds.
  • Reduce alcohol and caffeine as they put further stress on the adrenals.
  • Increase good quality dietary protein [12]
  • Aim for a diet low in the Omega-6 and high on Omega-3 [13]
  • Excluding inflammatory foods such as lectins, may help reduce symptoms.

Hypothyroidism dietary recommendations:

In general, the best diet for a person with hypothyroidism contains plenty of fruits and vegetables, good quality proteins, healthy fats and a moderate amount of healthful carbohydrates. A diet similar to the Paleo diet or a gluten-free Mediterranean diet.

However, it is important to remember that a personalised approach is always best as it considers the individual’s overall health, immunity, gut health, nutrient deficiencies, toxicity exposure and many other lifestyle factors.

Tips for maintaining a healthy weight

  • Get plenty of rest. Inadequate and poor-quality sleep have been linked to weight gain, particularly in the abdominal area [14].
  • Practice mindful eating. Mindful eating, which involves paying attention to what you’re eating, why you’re eating, and how fast you’re eating can help you develop a better relationship with food. Studies also show that it can help you lose weight [15] [16].
  • Try yoga or meditation. Yoga and meditation can help you de-stress and improve your overall health. Research also shows that these mind and body practices help you maintain a healthy weight [17].
  • Try a Paleo type diet that is low in carb and grains and high in good quality protein and fats. [18] [19].

How can I lose weight with an underactive thyroid? Tips for weight loss with hypothyroidism

Hypothyroidism may reduce your ability to lose weight [20]. Research shows that moderate to high intensity exercise such as fast-paced walking, running, hiking and rowing may help boost your thyroid hormone levels. In turn, this may help speed up your metabolism [21].

However, some people with hypothyroidism may not be able to do high intensity exercise due to debilitating fatigue, muscles aches and pains, swollen joints and lack of motivation and focus. For these patients we recommend that you see one of our experienced functional medicine practitioners who can create a personalised dietary and lifestyle programme that is suited to your symptoms and your lifestyle.

It is important to work with an experienced practitioner to individualise an approach that considers your genetics, health and lifestyle and unique situation. At the London Clinic of Nutrition we combine industry-leading nutrition and functional medicine expertise, alongside the latest in-house testing, so we can attend to all your health needs in one trip.

Get in touch

Find out more about our practitioners here, alternatively please feel free to get in touch to discuss your health concerns and to match you with the most suitable practitioner.



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