What to eat to support thyroid function

Written by Teagan Evans, University of Alberta Student in the Nutrition and Food Sciences program and reviewed by our Health Stand Nutrition Dietitian Team  

Hypothyroidism is a condition characterized by an underactive thyroid gland resulting in decreased thyroid hormone production. It is most commonly caused by an autoimmune disorder (also called Hashimoto’s thyroiditis) but can result from radiation treatments and surgery of the thyroid gland. The cause of hypothyroidism origin can be from genetic and / or environmental factors. 

Thyroid Hormone Production

The thyroid gland is essential to maintaining many of your body’s everyday functions. Thyroid hormones influence your temperature regulation, ability to utilize energy, and major organ function.  

The thyroid gland produces two types of thyroid hormones: T3 (triiodothyronine) and T4 (thyroxine). When we require increased production of these hormones, our brain sends signals of thyroid stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH) to the thyroid indicating that T4 and T3 production needs to increase. In response to TSH, the thyroid utilizes iodine (a chemical obtained from our everyday diet) to produce T3 and T4.  

Our brain-thyroid axis is based on a feedback system. When thyroid hormones levels are too high, levels in blood signal the brain to reduce production of TSH and TRH. When thyroid hormones in the blood are too low the brain gets signalled to produce more TSH and TRH, which results in increased thyroid hormone production. 

Below is a diagram that shows the simplified production of hormones from the thyroid gland: 

Symptoms & Testing

Hypothyroid symptoms can include the following: 

• Cold 
• Tired 
• Extremely dry skin  
• Forgetfulness, memory alterations 
• Depressive mood  
• Constipation  
• Weight gain 

To determine if you have hypothyroidism, your doctor will perform a thyroid-stimulating hormone (TSH) and T4 test. The TSH test is a blood test that indicates the level of TSH being produced. A high level of TSH means you have an underactive thyroid and your brain is trying to increase the thyroid hormone production, signalling hypothyroidism. The T4 test can be completed as a secondary test with a low level of T4 indicating hypothyroidism.   

Treatment of Hypothyroidism

Treatment and management of hypothyroidism is relatively simple and highly effective. Unfortunately, hypothyroidism cannot be cured, but proper medication makes it very easy to manage. The most common treatment of hypothyroidism is through a daily pill that contains a synthetic version of T4.  

Nutrition for Hypothyroidism

There are some nutritional considerations for hypothyroidism, particularly with medication consumption. It is best to take the thyroid pill on an empty stomach without food or other medications/supplements. Consuming a thyroid pill with food will reduce the absorption and effectiveness of the medication.  

For the following supplements, consume several hours before or after your thyroid pill: 

• Calcium  
• Magnesium 
• Iron 
• Multivitamins that contain calcium, magnesium, iron 
• Cholesterol-reducing medications (containing cholestyramine and colestipol) 
• Antacids that contain magnesium, calcium, aluminum 
• Ulcer medications  

Biotin is another supplement that has been known to interfere with the thyroid. Biotin will not influence the effectiveness of thyroid medication; however, it will affect clinical measurements of thyroid hormone and is best to avoid for at least a week prior to thyroid bloodwork.  

Similar to medications and supplements, these foods can be incorporated into your diet, but should be consumed several hours before or after thyroid medication.  

• Walnuts 
• Soy products 
• Cottonseed flour  
• High fiber meals 

Nutrition for Hypothyroidism: Iodine

There is no specific hypothyroidism diet. Maintaining a balanced diet will provide enough iodine for proper thyroid function. This involves fruits and vegetables, lean meat, carbohydrates, and healthy fats. The recommended dietary allowance of iodine for adults older than 19 years of age is 150mcg/day. If pregnant or lactating, the allowance increases to 220mcg and 290mcg, respectively.  

 Sources of iodine:  

• Table salt (Canada iodizes its salt) 
• Seaweed 
• Some dairy products – dependent on animal feed 
• Eggs 
• Fish 

Nutrition for Hypothyroidism: Selenium

Selenium is a mineral that has antioxidant properties, meaning it can contribute to the reduction of free radicals that are often associated with disease. Selenium has been shown to positively benefit thyroid function. Adults have a recommended amount of 55mcg/day, with an upper limit of 400mcg/day.  

Sources of selenium: 

• Brazil nuts  
• Oysters 
• Eggs 
• Fish  
• Cottage cheese  
• Couscous 

Nutrition for Hypothyroidism: Caffeine

Researchers have been studying the effect that caffeine has on the absorption of the T4 hormone, particularly with a thyroid medication named levothyroxine. In a 2008 study, researchers found that consuming coffee at the same time as thyroid medication reduced the absorption of T4. They discovered that it was best to wait 60 minutes after consuming medication to begin consuming coffee.  

For more information about nutrition for hypothyroidism talk to your Registered Dietitian and Doctor. 

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