Upper Limit of Selenium Intake Per Day
The tolerable upper intake level (UL) for selenium in adults is 255 μg/day, based on the most recent and rigorous evidence from the European Food Safety Authority. 1
Established Upper Limits
The European Food Safety Authority (EFSA) established a UL of 255 μg/day for adult men and women (including pregnant and lactating women) in 2023, based on alopecia as the critical endpoint. 1 This represents the most current and methodologically rigorous determination, derived from a lowest-observed-adverse-effect-level (LOAEL) of 330 μg/day identified in the large Selenium and Vitamin E Cancer Prevention Trial (SELECT), with an uncertainty factor of 1.3 applied. 1
For children, ULs are derived from the adult UL using allometric scaling (body weight^0.75). 1
Historical Context and Alternative Estimates
Earlier research from seleniferous areas in China suggested 400 μg/day as a maximum safe daily dietary selenium intake, with 600 μg/day representing the lower limit of individual safe intake. 2 However, the more conservative EFSA limit of 255 μg/day should be prioritized given its recent publication and rigorous methodology. 1
The Institute of Medicine's Recommended Dietary Allowance is 55 μg/day for adults, with typical U.S. intake estimated at 80 μg/day or greater. 3
Critical Toxicity Concerns
Selenium overexposure is positively associated with high-grade prostate cancer and type 2 diabetes, making adherence to upper limits essential. 4, 5, 6
Plasma Toxicity Thresholds
- Upper limits for plasma selenium before toxicity symptoms occur range from 6-12 μmol/L 4, 6
- However, chronic overexposure risks (diabetes, prostate cancer) occur at lower levels than acute toxicity 5, 6
Clinical Manifestations of Excess
- Alopecia (hair loss) is the earliest observable feature of selenium toxicity 1
- Nail damage and broken hair strands are characteristic signs of selenosis 2
- Selenium toxicity outbreaks have occurred due to misformulation of dietary supplements 4
Practical Clinical Guidance
Selenium intake from food should not be exceeded through supplementation, given the prostate cancer and diabetes risks. 5
Who Should Avoid Exceeding the UL
- Regular users of food supplements containing high daily doses of selenium 1
- Regular consumers of Brazil nuts 1
- Individuals with adequate baseline selenium status 5
Special Populations Requiring Higher Doses (Under Medical Supervision)
These therapeutic doses exceed the UL and require monitoring:
- Burns patients: up to 375 μg/day IV 4, 6
- Major trauma/cardiac surgery: 275 μg/day 4, 6
- Depleted patients: up to 200 μg/day with monitoring 4, 6
- Home parenteral nutrition: 60-100 μg/day 4, 6
High-dose selenium (1000-4000 μg/day) in ICU patients shows no consistent benefit and is advised against. 4, 6
Common Pitfalls to Avoid
- Do not assume selenium supplementation is universally beneficial - more than 99% of U.S. subjects are selenium replete from diet alone 3
- Do not use high-dose supplements without documented deficiency - the relationship between selenium and health outcomes is nonlinear, with harm occurring at both low and high levels 5
- Do not ignore supplement content - selenium-containing supplements should be used with caution, particularly in children, based on individual needs 1