The Healthspan Map · Nutrient

Selenium

Linked to getting too little

Where a shortfall of Selenium is linked — 14 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Nutrient or lever	Direction	Strength	Evidence type	What was found	Source
Selenium	Eat enough of	Emerging	Review / narrative	Low selenium status is inversely associated with anxiety (U-shaped risk); supplementation shows promise.	Trace-minerals & anxiety review 2023 (opens in a new tab)
Selenium	Eat enough of	Emerging	Review / narrative	Selenium supports thyroid hormone activation (T4->T3); low status can contribute to fatigue via thyroid function.	Nutrition & thyroid review (PMC11314468) (opens in a new tab)
Selenium	Eat enough of	Emerging	Review / narrative	Low selenium status is inversely associated with low mood/depression (U-shaped risk); evidence emerging.	Trace-minerals & mood review 2023 (opens in a new tab)
Selenium	Eat enough of	Moderate	Review / narrative	Selenium deficiency alters gut microbiota, is common in IBD (~31%), and can cause chronic diarrhoea and intestinal inflammation.	Selenium & gut microbiota/IBD (opens in a new tab)
Selenium	Eat enough of	Emerging	Cohort / observational	Serum selenium is associated with sleep; selenium supports antioxidant/immune pathways relevant to sleep regulation.	NHANES 2011-2016 (opens in a new tab)
Selenium	Eat enough of	Emerging	Systematic review	Selenium supports antioxidant defence in muscle; deficiency is linked to myopathy and reduced muscle performance.	Nutritional supplements & sarcopenia (opens in a new tab)
Selenium	Eat enough of	Moderate	Review / narrative	Selenium is built into sperm selenoproteins; adequate status supports sperm motility and guards against oxidative sperm damage.	Diet & male infertility (PMC7291266) (opens in a new tab)
Selenium	Eat enough of	Moderate	Review / narrative	Selenium deficiency impairs antiviral immunity, permits viral mutation to greater virulence, and tracks with worse viral-respiratory outcomes.	Nutrition & viral respiratory tract infections (Frontiers Immunol 2022) (opens in a new tab)
Selenium	Eat enough of	Moderate	Review / narrative	Selenium supports keratin and antioxidant defence; deficiency contributes to hair and nail changes.	Selenium & hair/nails (opens in a new tab)
Selenium	Eat enough of	Strong	RCT / meta-analysis	Selenium powers deiodinases (T4→T3) and glutathione peroxidase; supplementation lowers TPO antibodies in Hashimoto’s.	Micronutrients & autoimmune thyroid review (PMC12372124) (opens in a new tab)
Selenium	Eat enough of	Moderate	Review / narrative	Selenium supports antioxidant defence and T-cell/IFN-y responses; deficiency impairs immunity.	Selenium & immunity (opens in a new tab)
Selenium	Eat enough of	Strong	Established clinical	Severe deficiency causes Keshan disease, an endemic cardiomyopathy (heart failure, arrhythmia) in selenium-poor regions of China; selenium supplementation sharply reduced it.	NIH ODS / Keshan disease literature (opens in a new tab)
Selenium	Eat enough of	Strong	Established clinical	Severe deficiency causes Keshan disease, an endemic cardiomyopathy (heart failure, arrhythmia) in selenium-poor regions of China; selenium supplementation sharply reduced it.	NIH Office of Dietary Supplements — Selenium (opens in a new tab)
Selenium	Eat enough of	Moderate	Cohort / observational	Selenium is needed for sperm formation; deficiency is linked to male infertility.	NIH ODS – Selenium (opens in a new tab)

Linked to getting too much

Where an excess of Selenium is linked — 10 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Nutrient or lever	Direction	Strength	Evidence type	What was found	Source
Selenium	Don't overdo	Strong	Established clinical	Selenosis is a recognized toxidrome; NIH ODS and multiple human reports document anxiety, irritability, nervousness and insomnia from selenium overexposure (incl. a 201-person supplement outbreak).	Vinceti et al. 2013; NIH ODS; trace-minerals review (opens in a new tab)
Selenium	Don't overdo	Strong	Established clinical	Selenosis is a recognized toxidrome; NIH ODS and multiple human reports document anxiety, irritability, nervousness and insomnia from selenium overexposure (incl. a 201-person supplement outbreak).	NIH Office of Dietary Supplements — Selenium (opens in a new tab)
Selenium	Don't overdo	Moderate	Review / narrative	Selenium overexposure (selenosis) causes a neuropsychological syndrome including depression, irritability and fatigue.	Vinceti et al. 2013; NIH ODS (opens in a new tab)
Selenium	Don't overdo	Moderate	Established clinical	Selenium overexposure (selenosis) causes a neuropsychological syndrome including depression, irritability and fatigue.	NIH Office of Dietary Supplements — Selenium (opens in a new tab)
Selenium	Don't overdo	Moderate	Established clinical	Excess selenium (selenosis) causes GI upset - nausea, diarrhoea, vomiting - plus metallic taste and garlic breath.	Selenosis & GI (opens in a new tab)
Selenium	Don't overdo	Emerging	Review / narrative	Selenium toxicity (selenosis, usually from megadose supplements) can include nerve damage.	Selenosis & nerve damage (opens in a new tab)
Selenium	Don't overdo	Emerging	Review / narrative	Selenium is essential for sperm but has a narrow window; excess (selenosis) can reduce sperm quality.	Dietary antioxidants & male infertility – antioxidant paradox (PMC8003818) (opens in a new tab)
Selenium	Don't overdo	Emerging	Review / narrative	Selenium supplementation showed both beneficial and detrimental effects on influenza-vaccine immunity depending on dose/form; excess (selenosis) is immunotoxic.	Nutrition & viral respiratory tract infections (Frontiers Immunol 2022) (opens in a new tab)
Selenium	Don't overdo	Moderate	Review / narrative	Selenium toxicity (selenosis) causes hair loss and brittle, discoloured nails plus skin lesions.	Selenosis & hair/nails (opens in a new tab)
Selenium	Don't overdo	Emerging	Review / narrative	Very high selenium risks selenosis and may adversely affect thyroid/metabolic markers — the top of selenium’s own U-shape.	Minerals & thyroid review (PMC7574993) (opens in a new tab)