The Healthspan Map · Nutrient
Selenium
Compiled by Aamir Malik, PhD, Professor of Neuroengineering at Brno University of Technology, from published studies. He is a researcher, not a physician. Last updated 21 August 2026.
Linked to getting too little
| Condition or system | Direction | Strength | Evidence type | What was found | Source |
|---|---|---|---|---|---|
| Anxiety | 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) |
| Chronic fatigue / low energy | 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) |
| Depression / low mood | 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) |
| Digestive discomfort | 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) |
| Insomnia / poor sleep | 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) |
| Muscle & joint pain / weakness | 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) |
| Reproductive & sexual health | 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) |
| Respiratory infections & airway health | 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) |
| Skin, hair, nails & wound healing | 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) |
| Thyroid dysfunction | 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) |
| Weak immunity & chronic inflammation | 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) |
| Cardiovascular | 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) |
| Cardiovascular | 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) |
| Reproductive & Developmental | 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
| Condition or system | Direction | Strength | Evidence type | What was found | Source |
|---|---|---|---|---|---|
| Anxiety | 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) |
| Anxiety | 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) |
| Depression / low mood | 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) |
| Depression / low mood | 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) |
| Digestive discomfort | 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) |
| Peripheral neuropathy | 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) |
| Reproductive & sexual health | 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) |
| Respiratory infections & airway health | 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) |
| Skin, hair, nails & wound healing | 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) |
| Thyroid dysfunction | 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) |
The Healthspan Map is part of Fix the Floor, a book by Aamir Malik. About the book