A renewed interest in selenium has been spurred by the realization that sub-optimal levels, though not considered deficient, can negatively impact health. Perhaps even more compelling are the protective effects found when nutritional levels are slightly higher than recommended. These findings come amidst growing concern over selenium depleted soil concentrations throughout the world; a situation, which is highlighting thyroid and other selenium related health issues in affected regions. Another aspect to consider is the effects of drug induced selenium depletions. With increasing reliance on prescription drugs, the nutrient depletions they induce also warrant consideration. Having awareness can potentially avert unnecessary medical interventions to treat a symptom that may be corrected via diet or supplementation.
Selenium (Se) is an essential trace mineral that doesn’t get a lot of press, despite its vital and widespread functions in the body. In addition to thyroid and immune systems, selenium affects hormones, fertility, liver, brain, heart, and digestive processes, as well as musculoskeletal activities. Iodine is usually in the spotlight when it comes to minerals in the thyroid; however, selenium, iron and zinc also have essential roles that are interconnected. Diseases resulting from selenium deficiency have been recognized for years, but only recently have the effects of more subtle reductions been realized. With knowledge as to the potential health impacts of suboptimal serum levels, one can look closer at how certain medications may be contributing to the problem.
Selenium Depleting Drugs:
- Chemotherapy – Cisplatin
- Antipsychotic – Clozapine (Clozaril)
- Inhalant, topical and corticosteroids – Beclomethasone, Budesonide, Dexamthasone, Fluticasone, Hydrocortisone, Methylprednisolone, Mometasone Furoate, Prednisone, and Triamcinolone
- Statins: (suspected) negative effect on selenoprotein synthesis could explain statin induced myopathy.
- Anticonvulsant – Valproic acid (Depakote)
Medications come with the risk of side effects, but rarely are nutrient depletions acknowledged to be contributing factors. Theoretically, the prescribing physician and patient have considered and concluded the benefits of a drug outweigh any adverse effects. However, most doctors and even pharmacists aren’t well versed in drug induced nutrient depletions to initiate the conversation. Ironically, it’s not uncommon for the nutrients depleted to add to the problem the drug is supposed to treat, i.e. Statins and CoQ10. Since side effects aren’t usually recognized as being the result of a particular medication, another drug is often prescribed to treat the symptoms of the nutrient deficiency caused by the first. The cycle is perpetuated, when in fact, supplementing with the depleted nutrients may be all that is needed. With evidence of low selenium’s impact on thyroid health, making note of drugs that deplete it may prove beneficial, especially in populations where levels are already suboptimal.
The Role of Selenium:
Selenium plays an essential role in maintaining balance in cellular processes, namely those involving the immune system and thyroid function. It is central in synthesis and function of thyroid hormones. Selenium is also a key component of one of the most important antioxidant enzymes, “glutathione peroxidase”, which is a cofactor for glutathione. Glutathione is extremely important because it protects against free radicals, which underlie aging and disease processes. Basically it acts like rust proofing on your car protecting against oxidative damage to your bodily tissues. Low levels of both selenium and glutathione are associated with autoimmune thyroid disease and thyroid cancer. Some other related functions of selenium include:
- Converts thyroid hormone T4 to active T3
- Protects thyroid from excessive iodine exposure
- Protects against heavy metal toxicity
How Much Selenium Does One Need?
The answer isn’t a simple one. Since selenium has such a small range in between too little and too much, it is important to get it right. Currently the US Office of Dietary Supplements recommends approximately 55 micrograms per day for a typical adult, with increases for pregnant (60 mcg) and lactating (70mcg) women. Genetic variances in individuals can also be a factor in an individual’s selenium status. Research studies report supplementing 100 – 200 micrograms for conditions of deficiency. In areas of iodine deficiency and regions of low selenium intake, appropriate supplementation is reported to be 50-100 micrograms per day. With the lure of slightly higher levels as being beneficial, one should be cautious when supplementing so that it doesn’t become excessive, resulting in toxicity. As a result of mounting evidence of health benefits from levels slightly greater than recommended, some medical researchers argue the biochemical basis upon which current standards were derived.
With selenium-depleted areas scattered around the world, it is useful to be conscious of your intake if living in one of these areas. For instance, the selenium concentrations in British wheat can be as much as 50% lower than in wheat from the US or Canada. Not surprisingly, the UK is a population that is reported to have suboptimal levels. The foods supply is transient in the United States, which helps offset potential dietary deficiencies. To check regional concentrations, the US Geochemical Survey provides a detailed map. Although it ranks lower in selenium-depleted countries, the US is one of the highest in prescription usage. Therefore, if one of the previously listed drugs is used long term, additional selenium intake may be prudent.
Although evidence exists for supplementation in populations that need it for the various reasons aforementioned, an easy way to boost levels is from food sources. The following is a list of food sources with Brazil nuts being the highest.
Food Sources of Selenium:
- Brazil nuts
- Sunflower seeds
- Beef liver
- Herring fish
- Chicken breast
- Chia seeds
In conclusion, selenium is a nutrient worth noting. Despite mixed outcomes from compiled research studies as to supplementation effects on thyroid health and disease, it is clear that optimal levels are protective. It is important to bear in mind there are numerous incongruent variables impacting study outcomes. Similarly, there are variables affecting individual needs. Having an awareness of the factors that impact selenium status is a big step towards ensuring optimal levels. In order to best assess and customize individual needs, a knowledgeable health practitioner is recommended.
1. Dr. Axe.com. Selenium Benefits, Signs of Deficiency and Foods. Available at:https://draxe.com/selenium-benefits/
2. Ferrari, S. Fallahi, P. Antonelli, A. Benvenga, S. Environmental Issues in Thyroid Diseases. Front Endocrinol (Lausanne). 2017; 8:50.
3. Fitzpatrick, A. Jones, D. Glutathione Redox Control of Asthma: From Molecular Mechanisms to Therapeutic Opportunities. Antioxid Redox Signal. 2012 Jul 15; 17(2): 375–408.
4. Ghorbani A. Omidvar B. Parsi, A. Protective effect of selenium on cisplatin induced nephrotoxicity: A double-blind controlled randomized clinical trial. J Nephropathol. 2013;2(2):129-134.
5. Hurst, R. Armah, C. Dainty, J. et.al. Establishing optimal selenium status: results of a randomized, double-blind, placebo-controlled trial. Am J Clin Nutr 2010;91:923–31.
6. Negro, R. Attanasio, R. et. al. A 2016 Italian Survey about the Clinical Use of Selenium in Thyroid Disease. Eur Thyroid J. 2016 Sep;5(3):164-170.
7. National Institutes of Health Office of Dietary Supplements. Selenium: Fact Sheet. Available at:https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/
8. Moosmann, B. Behl, C. Selenoprotein synthesis and side-effects of statins. Lancet. 2004 Mar 13;363(9412):892-4.
9. Vaddadi, K. E Soosai, Vaddadi. Low blood selenium concentrations in schizophrenic patients on clozapine. Br J Clin Pharmacol. 2003 Mar; 55(3): 307–309.
10. Van Zuuren, E. Albusta, A. Carter, B. Selenium supplementation for Hashimoto’s thyroiditis. Cochrane Database Syst Rev. 2013 Jun 6;(6):CD010223.
11. Wiersinga, W. Clinical Relevance of Environmental Factors in the Pathogenesis of Autoimmune Thyroid Disease. Endocrinol Metab (Seoul). 2016 Jun; 31(2): 213–222.
12. Zimmermann, MB Köhrle J. The impact of iron and selenium deficiencies on iodine and thyroid metabolism: biochemistry and relevance to public health. Thyroid. 2002 Oct;12(10):867-78.