Selenium Does Not Cure Cancer
No, selenium does not cure cancer and should not be used as a general strategy for cancer prevention or treatment. The highest quality evidence from the SELECT trial involving 35,533 men showed no benefit for cancer prevention, and the American College of Chest Physicians explicitly recommends against selenium supplementation for lung cancer prevention (Grade 1B recommendation) 1, 2.
Evidence Against Selenium as Cancer Treatment
Major Clinical Trial Findings
The Selenium and Vitamin E Cancer Prevention Trial (SELECT) provides the most definitive evidence:
No reduction in cancer incidence: Selenium supplementation (200 mg L-selenomethionine) showed hazard ratios of 1.09 for prostate cancer and provided no significant benefit for lung cancer or other malignancies 2.
Trial terminated early: The Eastern Cooperative Oncology Group protocol E5597, which tested 200 mg selenized yeast for preventing second primary lung cancers in patients with resected early-stage NSCLC, was terminated early due to a nonsignificant trend between treatment groups 1.
Potential harm at higher baseline levels: Meta-analysis suggests selenium may actually increase cancer risk in populations with higher baseline selenium status (≥121.6 ng/mL) 3.
Guideline Recommendations
The American College of Chest Physicians states unequivocally that selenium "should not be used as a general strategy for lung cancer prevention" 1. This represents a Grade 1B recommendation—a strong recommendation based on moderate-quality evidence.
The American Cancer Society guidelines emphasize that while one experimental trial showed selenium supplements might reduce risk of certain cancers, repeated and well-controlled studies are needed to confirm this, and high-dose selenium supplements are not recommended 1.
The Prevention vs. Treatment Distinction
Prevention Context (Limited Benefit)
Selenium may have modest preventive effects only in populations with low baseline selenium status (serum <106 ng/mL) 3.
The Nutritional Prevention of Cancer trial showed a 44% decrease in lung cancer incidence, but further analysis revealed this benefit occurred only in the tertile with the lowest baseline plasma selenium levels 1.
Dietary selenium intake at recommended daily allowance levels (≥55 μg/day) showed a small protective effect (RR = 0.94) in meta-analysis, but this is for prevention in selenium-deficient populations, not treatment of existing cancer 4.
Treatment Context (No Evidence)
There is no credible evidence that selenium cures established cancer. The evidence base consists primarily of:
- Animal tumor models and cell culture studies 5, 6
- Theoretical mechanisms involving oxidative stress and apoptosis 6, 7
- No completed clinical trials demonstrating cure or significant survival benefit in cancer patients
Safety Concerns
Narrow Therapeutic Window
The margin between safe and toxic doses is extremely narrow 1.
Maximum supplemental dose should not exceed 200 micrograms per day 1.
High-dose selenium supplements carry risk of toxicity without proven benefit 1.
U-Shaped Dose-Response Curve
The relationship between selenium status and health outcomes follows a non-linear U-shaped curve, meaning both deficiency and excess can be harmful 7.
Clinical Bottom Line
Selenium supplementation should not be recommended for cancer cure or prevention in the general population. The evidence hierarchy clearly shows:
- Highest quality evidence (SELECT trial): No benefit, possible harm 2
- Professional society guidelines: Recommend against use 1
- Meta-analyses: Benefits limited to selenium-deficient populations for prevention only 3, 4
The only potential role for selenium is in populations with documented selenium deficiency, and even then, only for cancer prevention at physiologic doses obtained through diet (seafood, meats, grain products) rather than high-dose supplementation 1.
For patients seeking cancer treatment, selenium supplementation diverts attention from evidence-based therapies and carries risk of toxicity without proven benefit for morbidity, mortality, or quality of life.