From the Guidelines
Selenium supplementation is not consistently beneficial for thyroid health and should be approached with caution, as high doses have been advised against due to lack of consistent benefit and potential toxicity. When considering selenium for thyroid health, it's essential to weigh the potential benefits against the risks, particularly in terms of dosage. According to the ESPEN micronutrient guideline 1, a Danish RCT showed that selenium in doses of 100-300 mg/day decreased TSH and FT4 concentrations in euthyroid subjects with marginal selenium deficiency. However, similar effects were not observed in a UK population receiving the same dose 1. Key points to consider include:
- The potential benefits of selenium supplementation on thyroid function are not consistently supported across different populations 1.
- High doses of selenium (1000-4000 mg per day) have been advised against due to lack of consistent benefit and potential toxicity, as shown by a meta-analysis of studies in ICU patients 1.
- The recommended daily intake of selenium for adults is generally considered to be much lower, typically in the range of 55-70 mcg per day, to avoid toxicity.
- Food sources rich in selenium, such as Brazil nuts, seafood, eggs, and whole grains, can provide adequate intake without the risks associated with high-dose supplementation.
- Before starting any selenium supplement, especially for thyroid conditions, it is crucial to consult with a healthcare provider to discuss potential interactions with thyroid medications and to monitor thyroid function regularly.
From the Research
Selenium and Thyroid Disease
- Selenium is a micronutrient essential for the biosynthesis of selenoproteins containing selenocysteine, which are involved in thyroid hormone metabolism, redox state regulation, and maintenance of cellular homeostasis 2.
- The thyroid contains the highest amount of selenium per gram of tissue in adults, and selenium treatment has been shown to delay disease progression and improve the quality of life in patients with Graves' orbitopathy and Hashimoto's thyroiditis 2, 3.
- Selenium supplementation has been associated with decreased levels of anti-thyroid peroxidase antibody and improved thyroid ultrasound structure in patients with Hashimoto's thyroiditis 2, 4.
Benefits of Selenium Supplementation
- Selenium supplementation may alleviate symptoms or prevent progression to hypothyroidism and postpartum hypothyroidism in patients with autoimmune thyroiditis (AIT) 5.
- In pregnant females, adequate selenium intake has been shown to protect against miscarriages, preeclampsia/hypertension, preterm birth, and small-for-gestational-age infants' birth, and improve child's neuropsychological development 5.
- Selenium supplementation has been associated with improved quality of life, reduced oxidative stress and inflammatory status, and amended thyroid ultrasound structure and volume in patients with AIT 5, 4.
Considerations for Selenium Supplementation
- The safety of commercially available selenium formulations, doses, and duration of treatment should be determined, and proper guidelines are warranted to standardize the medical approach to selenium supplementation 5.
- Routine selenium supplementation implementation requires consideration of specific populational differences in natural selenium and iodine supply, the patient's clinical situation, individual response to supplementation, predisposition, and the status of other trace elements 5.
- The available evidence from trials does not support routine selenium supplementation in the standard treatment of patients with autoimmune thyroiditis or Graves' disease, but correction of moderate to severe selenium deficiency may offer benefits in preventing and treating these disorders 6.