Selenium side effects
Pro Research Analysisby 
Searched over 200M research papers
Selenium Side Effects: A Comprehensive Overview
Introduction to Selenium Toxicity
Selenium, an essential trace element, plays a crucial role in various biological processes, including antioxidant defense and thyroid hormone metabolism. However, its narrow therapeutic window means that both deficiency and excess can lead to significant health issues. This article synthesizes current research on the adverse effects of selenium, focusing on its impact on endocrine function, neurotoxicity, and other systemic effects.
Endocrine Disruption and Thyroid Function
One of the earliest and most notable toxic effects of selenium is its impact on endocrine function, particularly thyroid hormone synthesis. Chronic exposure to selenium at levels around 300 micrograms per day can disrupt the metabolism of thyroid hormones, growth hormone, and insulin-like growth factor-1 . Additionally, selenium supplementation has been shown to reduce thyroid autoantibody levels in patients with chronic autoimmune thyroiditis, although the clinical relevance of this finding remains uncertain .
Neurotoxicity and Nervous System Effects
Selenium's neurotoxic effects are well-documented, particularly with chronic exposure to inorganic selenium compounds. Symptoms such as lethargy, dizziness, motor weakness, and paresthesias have been reported. More concerning is the potential link between long-term selenium overexposure and an increased risk of amyotrophic lateral sclerosis (ALS) . These findings underscore the need for further research to fully elucidate the neurotoxic mechanisms of selenium.
Hepatotoxicity and Gastrointestinal Disturbances
High levels of selenium exposure can lead to hepatotoxicity and gastrointestinal issues. Symptoms such as nausea, vomiting, and diarrhea are common, particularly at higher doses. In a study involving high-dose selenium supplementation (1600 to 3200 micrograms per day) in prostate cancer patients, more selenium-related side effects were reported, although no serious toxicities were observed . Another study on septic shock patients found no obvious toxicity with high-dose selenium but also no clinical benefit .
Dermatologic and Immune System Effects
Exposure to high levels of selenium can also result in dermatologic issues such as nail and hair loss and dermatitis . Additionally, selenium can impair the activity of natural killer cells, which are crucial for immune defense . These effects highlight the importance of monitoring selenium levels to avoid immune system impairment.
Selenium in Cancer Treatment: Benefits and Risks
Selenium supplementation has been explored for its potential to alleviate the side effects of chemotherapy and radiotherapy in cancer patients. While some studies suggest a reduction in symptoms like fatigue and nausea, the evidence is not robust enough to recommend selenium supplementation universally for cancer patients Dennert2006Vieira2015Muecke2010. Moreover, the potential hazards of supplementing a trace mineral like selenium should be carefully considered.
Conclusion
Selenium is a double-edged sword: essential in small amounts but potentially harmful in excess. Its narrow safe range of intake necessitates careful monitoring, especially in populations at risk of overexposure. While selenium supplementation may offer some benefits, particularly in specific medical conditions, the potential for adverse effects cannot be overlooked. Further research is needed to better understand the full spectrum of selenium's impact on human health and to establish more precise guidelines for its safe use.
Sources and full results
Most relevant research papers on this topic
Adverse Health Effects of Selenium in Humans
Chronic exposure to selenium compounds can cause adverse health effects, including endocrine dysfunction, impairment of natural killer cells, hepatotoxicity, gastrointestinal disturbances, and dermatological effects.
Selenium neurotoxicity in humans: bridging laboratory and epidemiologic studies.
Chronic low-level selenium overexposure is associated with an increased risk of amyotrophic lateral sclerosis, highlighting the need for further research on its neurotoxic effects.
Selenium for alleviating the side effects of chemotherapy, radiotherapy and surgery in cancer patients.
Selenium supplementation may help reduce recurrent erysipela infections in cancer patients, but more randomized controlled trials are needed to confirm these findings.
A report of high-dose selenium supplementation: response and toxicities.
High-dose selenium supplementation showed no obvious serious toxicities in men with prostate cancer, but more subjects reported symptoms of toxicity.
DOI