Selenium for preventing cancer

M. Vinceti*, G. Dennert, C.M. Crespi, M. Zwahlen, M. Brinkman, M.P. Zeegers, M. Horneber, R. D'Amico, C. Del Giovane

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review


    BACKGROUND: This review is an update of the first Cochrane publication selenium for preventing cancer (Dennert 2011).Selenium is a metalloid nutritional and toxicological properties. Higher selenium exposure and supplements have been suggested to protect against several types of OBJECTIVES: Two research questions were addressed in this review: What evidence for:1. an aetiological relation between selenium exposure and risk in humans? and2. the efficacy of selenium supplementation for prevention in humans? SEARCH METHODS: We conducted electronic searches Cochrane Central Register of Controlled Trials (CENTRAL, 2013, Issue 1), (Ovid, 1966 to February 2013 week 1), EMBASE (1980 to 2013 week 6), (February 2004) and CCMed (February 2011). As MEDLINE now includes the indexed in CancerLit, no further searches were conducted in this 2004. SELECTION CRITERIA: We included prospective observational studies studies including sub-cohort controlled studies and nested case-control and randomised controlled trials (RCTs) with healthy adult participants of age and older). DATA COLLECTION AND ANALYSIS: For observational conducted random effects meta-analyses when five or more studies were for a specific outcome. For RCTs, we performed random effects meta- two or more studies were available. The risk of bias in observational assessed using forms adapted from the Newcastle-Ottawa Quality for cohort and case-control studies; the criteria specified in the Handbook for Systematic Reviews of Interventions were used to evaluate of bias in RCTs. MAIN RESULTS: We included 55 prospective observational (including more than 1,100,000 participants) and eight RCTs (with a 44,743 participants). For the observational studies, we found lower incidence (summary odds ratio (OR) 0.69, 95% confidence interval (CI) 0.91, N = 8) and cancer mortality (OR 0.60, 95% CI 0.39 to 0.93, N = 6) associated with higher selenium exposure. Gender-specific subgroup provided no clear evidence of different effects in men and women (P although cancer incidence was lower in men (OR 0.66, 95% CI 0.42 to than in women (OR 0.90, 95% CI 0.45 to 1.77, N = 2). The most pronounced decreases in risk of site-specific cancers were seen for stomach, prostate cancers. However, these findings have limitations due to study quality and heterogeneity that complicate interpretation of the summary statistics. Some studies suggested that genetic factors may modify the between selenium and cancer risk-a hypothesis that deserves further investigation.In RCTs, we found no clear evidence that selenium reduced the risk of any cancer (risk ratio (RR) 0.90, 95% CI 0.70 to studies, N = 4765) or cancer-related mortality (RR 0.81, 95% CI 0.49 to studies, N = 18,698), and this finding was confirmed when the analysis restricted to studies with low risk of bias. The effect on prostate imprecise (RR 0.90, 95% CI 0.71 to 1.14, four studies, N = 19,110), and analysis was limited to trials with low risk of bias, the interventions effect (RR 1.02, 95% CI 0.90 to 1.14, three studies, N = 18,183). The non-melanoma skin cancer was increased (RR 1.44, 95% CI 0.95 to 1.17, studies, N = 1900). Results of two trials-the Nutritional Prevention of Trial (NPCT) and the Selenium and Vitamin E Cancer Trial (SELECT)-also concerns about possible increased risk of type 2 diabetes, alopecia and dermatitis due to selenium supplements. An early hypothesis generated by that individuals with the lowest blood selenium levels at baseline could their risk of cancer, particularly of prostate cancer, by increasing intake has not been confirmed by subsequent trials. As the RCT overwhelmingly male (94%), gender differences could not be assessed. AUTHORS' CONCLUSIONS: Although an inverse association between exposure and the risk of some types of cancer was found in some studies, this cannot be taken as evidence of a causal relation, and should be interpreted with caution. These studies have many limitations, including issues with assessment of exposure to selenium and to its chemical forms, heterogeneity, confounding and other biases. Conflicting including inverse, null and direct associations have been reported for cancer types.RCTs assessing the effects of selenium supplementation on risk have yielded inconsistent results, although the most recent characterised by a low risk of bias, found no beneficial effect on more specifically on risk of prostate cancer, as well as little evidence influence of baseline selenium status. Rather, some trials suggest effects of selenium exposure. To date, no convincing evidence suggests selenium supplements can prevent cancer in humans.
    Original languageEnglish
    Article numberCD005195
    Number of pages193
    JournalCochrane Database of Systematic Reviews
    Issue number3
    Publication statusPublished - 1 Jan 2014


    • Case-Control Studies
    • Neoplasms [prevention & control]
    • Odds Ratio
    • Randomized Controlled Trials as Topic
    • Selenium [administration & dosage; adverse effects]
    • Sex Factors
    • Trace Elements [administration & dosage; adverse effects]
    • Female
    • Humans
    • Male


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