Written by Gabriele Dennert and the CAM-Cancer Consortium.
Updated October 20, 2013

Selenium – during cancer treatment

Abstract and key points

  • The trace element selenium is nutritionally essential for human health.
  • Supplemental selenium has been promoted for the treatment of cancer as well as the prevention or treatment of cancer-related symptoms and adverse effects of cancer therapy.
  • There is no evidence that selenium yeast supplements can prolong progression-free survival in people with non-small-cell lung cancer.
  • The role of selenium supplements during radio- or chemotherapy for cancer treatment, or the prevention of therapy-associated adverse effects, is unclear.
  • There is no evidence that selenium alleviates lymphoedema after surgery.
  • Selenium is toxic in high doses and might have adverse effects when taken at supranutritional doses for longer periods of time.

This summary is currently (April 2016) being updated, the version published here was last updated in October 2013. 

The trace element selenium is a nutrient essential to human health and occurs naturally in various food types. Inorganic forms (e.g. sodium selenite or selenite) and organic forms (e.g., selenomethionine) are both used in large numbers of selenium-containing medications, nutritional supplements or dietary aids that are promoted for medical or health purposes. These may contain either selenium alone (mono-supplements) or selenium in combination with other trace minerals as well as vitamins.

Supplemental selenium has been promoted for the treatment of cancer as well as the prevention or treatment of cancer-related symptoms and adverse effects of cancer therapy.

The role of selenium in the treatment of cancer, as well as the treatment or prevention of therapy-associated adverse effects, is unclear. One trial found an increased rate of remission in patients with non-Hodgkin lymphoma receiving CHOP-28 therapy plus selenium but the generalisability of these findings is uncertain. Another randomised clinical trial found no benefit of selenium yeast on five-year progression-free survival in people with resected stage I non-small-cell lung cancer.

Although a number of health problems have been linked to selenium deficiency, selenium is toxic in large doses and might have adverse effects when taken at supranutritional doses for longer periods of time. Long-term supplementation has caused symptoms of chronic overexposure and has also been linked to increased risks of developing type 2 diabetes mellitus.


Gabriele Dennert, CAM-Cancer Consortium. Selenium – during cancer treatment [online document]. http://cam-cancer.org/The-Summaries/Dietary-approaches/Selenium-during-cancer-treatment. October 20, 2013.

Document history

Summary first published in November 2010, authored by Gabriele Dennert.

Original summary divided into “Selenium – prevention” and “Selenium – during cancer treatment”, fully revised and updated in October 2013 by Gabriele Dennert.


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