Micronutrients & recovery
Long-term supplementation with 300 µg/day of selenium (as selenium-enriched yeast) in populations with moderately low baseline selenium status significantly increases all-cause mortality approximately 10 years after treatment cessation.
If you live in a region with low soil selenium (like parts of Europe), standard supplementation (100-200 µg/day) may be safe, but you should avoid high-dose supplements (300 µg/day or more) taken long-term. The study suggests that exceeding 300 µg/day of total selenium intake (diet + supplements) for 5+ years may increase your risk of death, particularly if you are under 65. Consult a doctor to check your baseline selenium levels before supplementing.
A 300 µg/d dose of selenium taken for 5 years in a country with moderately-low selenium status increased all-cause mortality 10 years later.
Why this rating
It is a randomized controlled trial, though the mortality endpoint was post-hoc and the sample size was limited (underpowered for some endpoints).
Source
Effect of long-term selenium supplementation on mortality: Results from a multiple-dose, randomised controlled trial
Margaret P. Rayman et al. · Free Radical Biology and Medicine · 2018
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