Exploring the Properties of Selenium Supplements

Selenium is an essential trace element that plays a vital role in numerous physiological processes. It is incorporated into selenoproteins—key enzymes that help protect cells from oxidative stress, support thyroid hormone metabolism, modulate immune responses, and contribute to overall metabolic regulation. In this blog, we explore the diverse properties of selenium supplements, including their benefits and potential risks. 

Antioxidant Function and Redox Balance 

One of the most celebrated properties of selenium is its antioxidant activity. Selenium is a critical component of glutathione peroxidase enzymes, which neutralize harmful reactive oxygen species (ROS) and protect cellular components (DNA, proteins, and lipids) from oxidative damage [1,16]. This antioxidant capacity is essential in combating chronic inflammation and may help reduce the risk of various degenerative diseases. 

Metabolic and Cardiovascular Health 

Emerging evidence suggests that selenium supplementation can influence metabolic health. Several clinical trials have examined its impact on glucose metabolism and lipid profiles, with some studies reporting improvements in insulin sensitivity and reductions in inflammatory markers such as high-sensitivity C-reactive protein (hs-CRP) [3,4,9]. Additionally, although findings on cardiovascular outcomes are mixed, the antioxidant action of selenium might contribute to lowering oxidative stress, a known risk factor for cardiovascular disease [2,7,11]. 

Thyroid Function and Autoimmunity 

The thyroid gland has one of the highest concentrations of selenium in the body. Selenoproteins are essential for the conversion of thyroxine (T4) into the more active triiodothyronine (T3), and they help protect thyroid cells against oxidative damage. In patients with autoimmune thyroiditis, supplementation has been shown to reduce thyroid autoantibody levels, which may translate into improved thyroid function and overall well-being [6,14]. 

Cancer Prevention Potential 

Selenium’s role in cancer prevention has been the subject of extensive research. Some studies have suggested that selenium’s incorporation into selenoproteins may help inhibit carcinogenesis by reducing oxidative DNA damage and modulating cell signaling pathways. However, the evidence is not yet definitive, and the potential benefits may depend on the form of selenium used and the baseline selenium status of the individual [1,10]. 

Effects on Mood and Cognitive Health 

Interestingly, selenium supplementation has also been linked with improvements in mood. Research indicates that individuals with low dietary selenium may experience higher levels of anxiety and depression, and short-term supplementation has been associated with enhanced mood and reduced anxiety symptoms [12]. While these findings are promising, further research is necessary to understand the mechanisms behind selenium’s influence on mental health. 

Safety, Dosage, and Potential Toxicity 

Like many micronutrients, selenium has a narrow therapeutic window. Most supplements are formulated at doses around 200 µg/day, which are generally considered safe and effective. However, high-dose selenium supplementation can lead to toxicity—with symptoms such as gastrointestinal upset, hair and nail brittleness—and, in some studies, even increased mortality risk [5,13]. These findings underscore the importance of adhering to recommended dosages and consulting healthcare professionals before starting supplementation. 

Conclusion 

Selenium supplements offer a range of potential health benefits, from enhancing antioxidant defenses and supporting thyroid function to modulating metabolic and cardiovascular health. Nonetheless, the effects of supplementation are dose-dependent and can vary based on individual selenium status and the chemical form of the supplement. Ongoing research continues to refine our understanding of the optimal use of selenium for preventive health care. 

References 

1. Schrauzer GN. Nutritional Selenium Supplements: Product Types, Quality, and Safety. J Am Coll Nutr. 2001;20(1):1–4. 

2. Stranges S, Marshall JR, Trevisan M, et al. Effects of Selenium Supplementation on Cardiovascular Disease Incidence and Mortality: Secondary Analyses in a Randomized Clinical Trial. Am J Epidemiol. 2006;163:694–699. 

3. Stranges S, Marshall JR, Natarajan R, et al. Effects of Long-Term Selenium Supplementation on the Incidence of Type 2 Diabetes: A Randomized Trial. Ann Intern Med. 2007;147:217–223. 

4. Tabrizi R, Akbari M, Moosazadeh M, et al. The Effects of Selenium Supplementation on Glucose Metabolism and Lipid Profiles Among Patients with Metabolic Diseases: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Horm Metab Res. 2017. 

5. Reid ME, Stratton MS, Lillico AJ, et al. A report of high-dose selenium supplementation: response and toxicities. J Trace Elem Med Biol. 2004;18:69–74. 

6. Toulis KA, Anastasilakis AD, Tzellos TG, et al. Selenium Supplementation in the Treatment of Hashimoto’s Thyroiditis: A Systematic Review and Meta-Analysis. Thyroid. 2010;20(10):? (accessed from the provided document). 

7. Rees K, Hartley L, Day C, Clarke A, Stranges S. Selenium Supplementation for the Primary Prevention of Cardiovascular Disease (Protocol). Cochrane Database Syst Rev. 2012;Issue 2:CD009671. 

8. Kieliszek M, Lipinski B. Selenium supplementation in the prevention of coronavirus infections (COVID-19). Med Hypotheses. 2020;143:109878. 

9. Farrokhian A, Bahmani F, Taghizadeh M, et al. Selenium Supplementation Affects Insulin Resistance and Serum hs-CRP in Patients with Type 2 Diabetes and Coronary Heart Disease. Horm Metab Res. 2016;48:263–268. 

10. Gromadzińska J, Reszka E, Bruzelius K, et al. Selenium and cancer: biomarkers of selenium status and molecular action of selenium supplements. Eur J Nutr. 2008;47(Suppl 2):29–50. 

11. Hardy G, Hardy I, Manzanares W. Selenium Supplementation in the Critically Ill. Nutr Clin Pract. 2012;27(1):21–33. 

12. Benton D, Cook R. The Impact of Selenium Supplementation on Mood. Biol Psychiatry. 1991;29:1092–1098. 

13. Rayman MP, Winther KH, Pastor-Barriuso R, et al. Effect of long-term selenium supplementation on mortality: results from a multiple-dose, randomized controlled trial. Free Radic Biol Med. 2018. doi:10.1016/j.freeradbiomed.2018.02.015. 

14. Wichman J, Winther KH, Bonnema SJ, Hegedüs L. Selenium Supplementation Significantly Reduces Thyroid Autoantibody Levels in Patients with Chronic Autoimmune Thyroiditis: A Systematic Review and Meta-Analysis. Thyroid. 2016;26(12):1681–1692. 

15. Savory LA, Kerr CJ, Whiting P, et al. Selenium Supplementation and Exercise: Effect on Oxidant Stress in Overweight Adults. Obesity (Silver Spring). 2011; doi:10.1038/oby.2011.83. 

16. Zakeri N, Rezaei Kelishadi M, Asbaghi O, et al. Selenium Supplementation and Oxidative Stress: A review. PharmaNutrition. 2021; doi:10.1016/j.phanu.2021.100263.