Selenium Interactions Overview

Additonal Details

Is Selenium Safe? Are There Any Warnings?

LIKELY SAFE: Oral use of selenium in amounts below 400 mcg daily is generally considered safe for short-term use. However, there are concerns about its long-term safety, with evidence linking higher dietary intake and supplements to an increased risk of type 2 diabetes.

POSSIBLY UNSAFE: High oral doses or prolonged use above 400 mcg daily may elevate the risk of selenium toxicity and contribute to the development of type 2 diabetes. Caution is advised, especially for long-term use.

CHILDREN: Selenium is considered possibly safe for short-term oral use in specified doses for different age groups. Long-term use in children raises some safety concerns.

PREGNANCY: Short-term oral use below 400 mcg daily is possibly safe during pregnancy, but excessive doses may pose a risk of toxicity.

LACTATION: Similar to pregnancy, short-term oral use below 400 mcg daily is possibly safe during lactation. However, excessive doses may lead to toxicity.

Standardization & Formulation

In clinical research, selenium is often included in multivitamins or used as a standalone supplement. Different chemical forms are available, with selenomethionine or selenocysteine being common in dietary supplements. Selenium-enriched yeast, containing selenomethionine, is prevalent in various products.

Pharmacokinetics

Absorption: Approximately 80% of dietary selenium is absorbed, with selenomethionine showing higher efficiency than other forms. Bioavailability varies depending on the source, with selenium-enriched yeast having higher bioavailability than inorganic selenium.

Distribution: Selenium accumulates predominantly in the kidneys and is distributed to various tissues, including the skin. Selenomethionine provides a means of reversible selenium storage in organs and tissues.

Metabolism: The metabolism of selenium involves conversion to hydrogen selenide, crucial for the activity of selenoproteins. Selenomethionine, a primary organic form, serves as a storage form releasing selenium upon protein catabolism.

Excretion: Urinary selenium excretion is influenced by the form consumed, with selenomethionine leading to greater excretion than selenite.

Mechanism of Action

Antineoplastic Effects: Selenium demonstrates anticancer effects by inducing apoptosis and reducing reactive oxygen species (ROS) formation. Different selenium compounds vary in their effectiveness against cancer cells.

Antioxidant Effects: Selenium acts as an antioxidant at lower concentrations, activating glutathione peroxidase (GSH-Px) to handle free radicals. Paradoxically, at higher concentrations, it can increase cellular oxidation.

Bone Effects: Despite associations between higher selenium levels and bone health, clinical studies do not consistently show improvement in bone turnover markers with selenium supplementation.

Cardiovascular Effects: Selenium may prevent oxidative modification of low-density lipoproteins (LDLs) and has implications in cardiovascular diseases.

Fertility Effects: Selenium is essential for testosterone biosynthesis and sperm development. Low selenium levels are linked to decreased male fertility.

Immune System Effects: Selenium enhances immunologic function, increasing interleukin-2 (IL-2) activity. It has potential applications in treating AIDS, and selenium deficiency is common in HIV-positive individuals.

Neurologic Effects: Selenium's role in reducing oxidative stress makes it of interest in neurodegenerative diseases like Alzheimer's, although conclusive evidence is lacking.

Psychological Effects: Low selenium levels may be associated with increased incidence of depression, anxiety, and other mood disorders.

Drugs that interact with Selenium