Selenium

Symptoms of toxicity may include loss of, or brittle hair or nails, skin rash, fatigue, nausea, diarrhea, irritability and peripheral neuropathy.

Selenium and cancer: A Cochrane Review by Dennert G et al used 6 randomized controlled clinical trials and 49 observational studies to calculate the odds ratio of cancer incidence and mortality with selenium intake. A higher selenium intake was associated with a 31% lower risk of cancer (OR 0.69, 95% CI 0.53 to 0.91 ) and a 45% lower risk of mortality (OR 0.55, 95% CI 0.36 to 0.83). The risk reduction of cancer was greater in men than women 34% vs 10%. Despite findings of the analysis, the study concludes that a low selenium level cannot be directly linked with an increased risk of cancer and there may have been limitations of possible bias, quality, and design of the studies reviewed. (4)