Is Selenium safe?

Introduction

Selenium is a metalloid with both essential nutritional and toxicological properties. It plays a crucial role in various biological processes, but its safe range of intake is very narrow. This synthesis aims to evaluate the safety of selenium based on multiple research studies.

Key Insights

Narrow Safe Range and Toxicity:
- Selenium has a very narrow safe range of intake, with both deficiency and excess posing health risks .
- Acute selenium intoxication can lead to severe adverse effects, including neurotoxicity and even death .
Chronic Overexposure Risks:
- Chronic low-level overexposure to selenium, particularly its inorganic compounds, has been associated with neurological issues such as lethargy, dizziness, motor weakness, and an increased risk of amyotrophic lateral sclerosis .
- Long-term exposure to selenium in drinking water at levels previously considered safe may still pose health risks, suggesting the need for reassessment of these limits.
Form-Dependent Toxicity:
- The toxicity of selenium is highly dependent on its chemical form, with inorganic selenium compounds generally being more toxic than organic forms .
- Selenium-containing yeast, an organic form, is considered a safer source of dietary selenium.
Supplementation Studies:
- Selenium supplementation in patients with resected non-small-cell lung cancer showed no significant benefit over placebo in preventing second primary tumors, although it was deemed safe in the study context .
- No increase in diabetes mellitus or skin cancer was detected in these supplementation trials .
Environmental and Public Health Concerns:
- High selenium concentrations in soil and groundwater, particularly in agricultural regions, pose significant public health risks due to potential bioaccumulation and toxicity .

Conclusion

Selenium is essential for human health but has a very narrow safe range of intake. Acute and chronic overexposure can lead to severe health issues, particularly neurotoxicity. The form of selenium significantly influences its toxicity, with inorganic forms being more harmful. While selenium supplementation has been shown to be safe in certain clinical trials, it did not confer additional health benefits. Environmental selenium contamination remains a public health concern, necessitating further research and reassessment of safe exposure limits.

Summary

Consensus Meter

Introduction

Key Insights

Conclusion

Sources and full results

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.

The need for a reassessment of the safe upper limit of selenium in drinking water.

The safe upper limit of selenium in drinking water should be reduced to 1 g/l due to potential health risks at lower levels than previously thought.

Accidental death from acute selenium poisoning

Acute selenium poisoning can be fatal, highlighting the risks of not critically evaluating Internet information and the myth that natural therapies are inherently safe.

A phase III, intergroup, randomized, double-blind, chemoprevention trial of selenium (Se) supplementation in resected stage I non-small cell lung cancer (NSCLC).

Selenium supplementation was safe but showed no significant benefit over placebo in resected stage I non-small cell lung cancer patients.

Randomized, double-blind, placebo-controlled, phase III chemoprevention trial of selenium supplementation in patients with resected stage I non-small-cell lung cancer: ECOG 5597.

Selenium supplementation was safe but showed no benefit in preventing second primary tumors in patients with resected stage I non-small-cell lung cancer.

Selenium: Significance, and outlook for supplementation.

Selenium supplementation is a safe and effective method to enhance dietary selenium intake, with yeast being a safe and natural source.

Acute selenium toxicosis in a dog.

A toxic dose of selenium, inadvertently combined with a vitamin E preparation, led to pulmonary edema and death in a 3-year-old Chihuahua dog.

An Overview of Selenium Uptake, Metabolism, and Toxicity in Plants

Low doses of selenium protect plants from abiotic stresses and can help overcome se deficiency and toxicity, but excessive selenium intake can cause toxicity.

Hazardous concentrations of selenium in soil and groundwater in North-West India.

Toxic selenium concentrations in soil and groundwater in North-West India may be due to intensive irrigation practices and high levels of As, Mo, and U in groundwater, making it unsuitable for drinking purposes.

The toxicity of different selenium forms and compounds – Review

High selenium intake can induce toxicity, emphasizing the need to assess the health risk of various selenocompounds as nutritional supplements.

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