From the Guidelines
A vegan diet does not directly cause hypothyroidism, but it may increase risk factors if not properly balanced. Vegans should ensure adequate intake of nutrients important for thyroid function, particularly iodine, selenium, zinc, and iron, as a diet poor in animal source foods can lead to various nutritional deficiencies, including iodine deficiency, which is crucial for thyroid function 1. Iodine can be obtained from iodized salt, seaweed, and fortified foods; selenium from Brazil nuts and whole grains; zinc from legumes, nuts, and seeds; and iron from leafy greens, legumes, and fortified foods.
- Key nutrients to focus on for thyroid health on a vegan diet include:
- Iodine: essential for thyroid hormone production
- Selenium: acts as an antioxidant to protect the thyroid gland
- Zinc: plays a role in thyroid hormone production and conversion
- Iron: necessary for the production of thyroid hormones
- Vitamin B12 supplementation (typically 25-100 mcg daily) is essential for vegans as it's naturally found only in animal products, and its deficiency can lead to general malnutrition and poorer health 1. Some plant foods like soy, cruciferous vegetables, and certain fruits can contain goitrogens that may affect thyroid function when consumed raw in large amounts, but cooking typically deactivates these compounds.
- If you have existing thyroid issues or a family history of thyroid disease, consult with a healthcare provider who can monitor your thyroid function and recommend appropriate dietary adjustments or supplements while following a vegan diet, as many people on plant-based diets are in the deficient or borderline-deficient range for certain nutrients, despite the need for supplementation being well-publicized 1.
From the Research
Vegan Diet and Hypothyroidism
- A vegan diet may lead to iodine deficiency, which is a common cause of acquired hypothyroidism worldwide 2.
- A case study presented a 23-month-old boy diagnosed with iodine deficiency hypothyroidism induced by a vegan diet, highlighting the risk of iodine deficiency in children on a vegan diet after discontinuation of breast/formula feeding 2.
- A study found that vegans had higher thyroglobulin (Tg) levels compared to pescatarians, and vegans not consuming iodine-containing supplements had higher Tg levels than supplement users 3.
- The prevalence of subclinical hypothyroidism was low in a study of vegans, lacto-ovo vegetarians, and pescatarians, and the median urinary iodine concentration was below WHO thresholds for all dietary groups 3.
Nutrient Deficiencies and Hypothyroidism
- Vegan diets may be associated with low intake of vitamins B2, B12, D, iodine, zinc, calcium, potassium, and selenium, which can increase the risk of hypothyroidism 4.
- A systematic review found that vegan diets are lower in protein intake and may be associated with deficiencies in micronutrients such as vitamin B12, zinc, calcium, and selenium 4.
- However, a study found that a vegan diet tended to be associated with lower risk of hypothyroid disease, although the results were not statistically significant 5.
Dietary Approaches and Thyroid Function
- Iodine supplementation has been shown to be beneficial in preventing severe thyroid disease, but excess iodine can cause thyroid disorders 6.
- Selenium and zinc supplementation may be beneficial in specific populations, but other minerals and complementary medicines have little to no evidence of impact on thyroid disorders 6.
- Avoidance of gluten and dairy may have positive impacts in patients with concomitant sensitivities, but avoidance of cruciferous vegetables and soy has little proven benefit in patients with thyroid disorders 6.