Is a higher selenium intake associated with a reduced risk of thyroid cancer? Original paper

This prospective cohort study in postmenopausal women reported no association between selenium intake and thyroid cancer risk.

This Study Summary was published on January 5, 2023.


Normal thyroid function depends on adequate intake of certain micronutrients, including iodine and selenium. Selenium is essential for the synthesis and metabolism of thyroid hormones. Additionally, selenium-containing proteins play a critical role in the balance of antioxidant and oxidant systems in the body, and oxidative stress is implicated in the development of thyroid cancer.[1]

The study

This prospective cohort study examined the association between selenium intake and thyroid cancer risk in 147,348 postmenopausal women (ages 50–79) over an average follow-up period of 16.4 years. Selenium intake was assessed at baseline using a food frequency questionnaire and another questionnaire on supplement use.

The primary outcome was newly diagnosed thyroid cancer cases, including papillary cancer, follicular cancer, medullary cancer, anaplastic cancer, and carcinoma not otherwise specified.

The analyses attempted to control for a number of potentially confounding factors, including sociodemographic factors, family history of thyroid cancer, history of hormone therapy, smoking, physical activity, BMI, and total energy intake.

The results

During follow-up, there were 442 thyroid cancer cases. There was no association between thyroid cancer risk and total selenium intake. There was also no association between thyroid cancer risk and dietary selenium intake (i.e., not including selenium from supplements) or thyroid cancer risk and supplemental selenium intake.


In this study, the average selenium intake exceeded the Recommended Daily Allowance (RDA). Thus, the null findings may be a product of sufficient selenium intake in this population at large, assuming that selenium inadequacy or deficiency increases thyroid cancer risk.

A limitation of this study is that selenium intake was only assessed at baseline, so the study did not account for potential changes in selenium intake over time.

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This Study Summary was published on January 5, 2023.


  1. ^Alessio Metere, Francesca Frezzotti, Claire Elizabeth Graves, Massimo Vergine, Alessandro De Luca, Donatella Pietraforte, Laura GiacomelliA possible role for selenoprotein glutathione peroxidase (GPx1) and thioredoxin reductases (TrxR1) in thyroid cancer: our experience in thyroid surgeryCancer Cell Int.(2018 Jan 15)