Record ID: MS-N086 · Family: Nutrients and supplements / cancer prevention · Clinical question: Do selenium or high-dose vitamin E supplements prevent prostate cancer?

Evidence label: Large randomized evidence shows no prevention benefit; vitamin E 400 IU/day increased prostate-cancer incidence.

Evidence at a glance

• Benefit: None demonstrated for selenium, vitamin E or their combination.
• Certainty: High for the tested doses and formulations.
• Risk: Vitamin E increased prostate-cancer incidence; high-dose supplements can also have bleeding or toxicity concerns.
• Cancer control: Prevention was not achieved; these supplements do not treat prostate cancer.

What was studied

SELECT randomized 35,533 cancer-free men at 427 sites to selenium 200 micrograms/day, vitamin E 400 IU/day, both, or placebo. The trial was stopped early for lack of efficacy; follow-up continued after supplementation ended.

The updated analysis compared prostate-cancer diagnoses across all four groups using 99% confidence intervals because of multiple comparisons.

What the results show

Prostate cancer developed in 620 men assigned vitamin E versus 529 assigned placebo: HR 1.17 (99% CI 1.004–1.36; P=0.008), an absolute increase of 1.6 cases per 1,000 person-years.

Selenium alone was also not beneficial: 575 cases, HR 1.09 (99% CI 0.93–1.27). The combination had 555 cases, HR 1.05 (99% CI 0.89–1.22). The findings contradict the assumption that antioxidant supplements are harmless prevention.

Important limits

• The result applies to the tested L-selenomethionine and alpha-tocopheryl acetate doses, not ordinary food intake.
• Participants were generally selenium-replete; effects can differ by baseline status, but subgroup hypotheses do not restore overall efficacy.
• Screening and biopsy patterns can influence diagnosis, although randomized allocation protects the main comparison.
• This was prevention in men without prostate cancer, not treatment after diagnosis.

Safety and practical context

Do not use high-dose vitamin E or selenium to prevent prostate cancer. Vitamin E can increase bleeding risk with anticoagulants or antiplatelet drugs; excess selenium can cause hair and nail changes, gastrointestinal symptoms, neuropathy and other toxicity.

Questions for the care team

• Why am I taking this dose—documented deficiency or cancer prevention?
• Could it interact with anticoagulants, antiplatelet drugs or surgery?
• What is my total intake from multivitamins and separate products?
• Would food-based nutrition meet the goal without high-dose supplementation?

Sources checked

• Initial SELECT report, JAMA 2009 (PMID 19066370)
• Updated SELECT prostate-cancer analysis, JAMA 2011 (PMID 21990298)

Funding and conflicts: SELECT was coordinated and funded by the US National Cancer Institute with other public support; study supplements were supplied by manufacturers. The papers report sponsor and author disclosures.

Last literature search: October 20, 2026 · Record appraisal: October 20, 2026

Educational information only. This record is not a prescription and does not replace advice from the oncology team, registered dietitian or oncology pharmacist.