Selenium

How it works

It is incorporated into selenoproteins such as glutathione peroxidases that contribute to antioxidant defence and other metabolic functions.

Prescribing in practice

• Selenium has a narrow margin between adequacy and toxicity; excessive intake causes selenosis with features such as hair and nail changes, gastrointestinal upset and neurological effects.
• Supplementation is indicated mainly to prevent or treat deficiency, including in long-term parenteral nutrition rather than for unselected populations.
• Doses should reflect deficiency status and other sources of intake; refer to current prescribing references.

Monitoring

Selenium status may be assessed where deficiency or excess is suspected, particularly during long-term parenteral nutrition.

Counselling the patient

• Take only the dose recommended, as too much selenium can be harmful.
• Avoid combining several supplements that all contain selenium.
• Report symptoms such as hair loss, brittle nails or a garlic-like breath odour.

Evidence & guidelines

The role of selenium as an essential trace element and the consequences of deficiency are well established in nutritional science.