Thyroid Function and Nutrition

What is the Thyroid Gland?

The thyroid is a brownish- red, highly vascular two inch gland shaped like a butterfly. The thyroid is located just below the surface of the skin and is therefore readily accessible for examination.

Why is the Thyroid important?

The functionality of the thyroid gland will affect your body’s overall wellness. Your thyroid gland is responsible for manufacturing enough thyroid hormone to trigger your cells to perform and function at a certain rate. The thyroid hormones regulate vital functions like:

  • Breathing
  • Heart rate
  • Central and peripheral nervous system function
  • Body weight
  • Muscle strength
  • Menstrual cycles
  • Body temperature
  • Cholesterol levels
  • Metabolism

The levels of hormones secreted by the thyroid are controlled by thyroid-stimulating hormone released by the pituitary gland.

Thyroid Problems

When the T3 and T4 hormone levels become too high or too low, your body will develop hyperthyroidism or hypothyroidism. Hyperthyroidism occurs when there is too much T3 and T4 in your system. Symptoms of hyperthyroidism include:

  • Anxiety
  • Irritability or moodiness
  • Weight loss
  • Nervousness
  • Hyperactivity
  • Sweating or sensitivity to high temperatures
  • Hand trembling
  • Hair loss
  • Missed or light menstrual periods

Hypothyroidism occurs when there is too little T3 and T4 in your system. Symptoms of hypothyroidism include:

  • Trouble sleeping
  • Tiredness and fatigue
  • Difficulty concentrating
  • Weight gain
  • Dry skin and hair
  • Depression
  • Sensitivity to cold temperature
  • Frequent, heavy periods
  • Joint and muscle pain

What can cause reduced thyroid hormone activity?

  • Estrogen dominance
  • Stress and cortisol
  • Inflammation and cytokines
  • Obesity
  • Nutritional deficiencies (iodine, zinc, selenium)
  • Foods like soy and gluten

Key Nutrients involved in Thyroid Function

Many nutritional factors play a role in optimizing thyroid function. However, both nutrient deficiencies and excesses can trigger or exacerbate symptoms. This is why it is important to work in collaboration with a physician (like a Nutritionist, Naturopath, Doctor, etc) to determine nutritional status for optimal thyroid health.

  • Iodine is an essential component of the thyroid hormones, T4 and T3 and is necessary for normal growth, development, and metabolism during pregnancy, infancy and throughout life. Iodine deficiency is the most common cause of preventable mental impairment worldwide. . New Zealand’s soil is naturally quite low in iodine, therefore most of our foods are too. Universal salt iodization (USI) has been introduced in many countries as a cost-effective and sustainable way to eliminate iodine deficiency disorders for more than 25 years. Foods high in iodine include seaweed (try the Ceres Roasted Seaweed as a snack), cranberries, fish, eggs and potatoes.

  • Selenium- The highest concentration of selenium is found in the thyroid gland, and it’s been shown to be a necessary component of enzymes integral to thyroid function. Selenium is an essential trace mineral and has been shown to have a profound effect on the immune system, cognitive function, fertility in both men and women, and mortality rate. Incorporating 2 x brazil nuts in your daily diet will give you your daily selenium dose.

  • Zinc is required for the conversion of T4 to T3. Conversely, thyroid hormones are essential for the absorption of zinc, and hence hypothyroidism can result in acquired zinc deficiency. Foods high in Zinc include pumpkin seeds, garlic, sesame seeds, lamb, grass fed beef and chickpeas.

  • Goitrogens, which exist naturally in foods, can cause goiter by blocking the uptake of iodine from the blood by the thyroid. Goitrogens are inactivated by heating or cooking. Most goitrogens are not of clinical importance unless they are consumed in large amounts or there is coexisting iodine deficiency.

Ensure you are having a diet rich in wholefoods with adequate amounts of iodine, selenium and zinc. Maintain a regular exercise regime, get 7-9 hours of sleep per night, manage stress and avoid synthetic chemicals found in conventional food items, body products and food containers when possible.



  1. Zimmermann MB. Iodine deficiency.Endocr Rev. 2009;30:376–408. [PubMed]
  3. Ogunyemi DA. Autoimmune thyroid disease and pregnancy. eMedicine website. Updated March 8, 2012.
  4. Dietary supplement fact sheet: iodine. Office of Dietary Supplements website. Reviewed June 24, 2011. Accessed January 17, 2012.


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