Selenium Selenomethionine
Also known as: Selenium, organic selenium, SeMet, Selenomethionine
Overview
Selenomethionine (SeMet) is an essential trace element and the predominant organic form of selenium found in food and supplements. It is a selenium-containing amino acid, where selenium is incorporated into the methionine molecule. Naturally occurring in soil, water, and foods like Brazil nuts and seafood, selenomethionine is highly bioavailable and serves as a crucial selenium reservoir in the body. Supplementation with selenomethionine is primarily used to address selenium deficiency, bolster antioxidant defenses, and modulate immune and thyroid function. Its high bioavailability and lower toxicity risk compared to inorganic selenium forms make it a preferred choice for supplementation. Research on selenium, particularly selenomethionine, is extensive, with multiple systematic reviews and meta-analyses supporting its role in conditions like thyroid autoimmune diseases and its general antioxidant effects. The field is considered mature, with robust evidence for certain indications.
Benefits
Selenomethionine supplementation offers several evidence-based benefits, particularly for individuals with autoimmune thyroid conditions. The most significant effect is a substantial reduction in thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb) in patients with Hashimoto thyroiditis. Meta-analyses, such as a 2024 review of 31 cohorts, indicate a weighted mean difference in TPOAb reduction of approximately -284 U/mL (p < 0.05) after 3-6 months of supplementation. A 2023 meta-analysis of 7 RCTs also confirmed a significant decrease in TPOAb after 6 months. Additionally, it has been shown to reduce thyroid-stimulating hormone (TSH) levels in Hashimoto thyroiditis patients not on thyroid hormone replacement therapy. Beyond thyroid-specific effects, selenomethionine contributes to decreased oxidative stress markers, such as malondialdehyde (MDA), due to its role in selenoproteins like glutathione peroxidases. While some limited data suggest potential mood improvements, this area requires further research. Benefits are most pronounced in selenium-deficient populations and those with autoimmune thyroid diseases. The observed antibody reductions are statistically significant with moderate effect sizes, though the direct clinical impact on thyroid function and symptoms warrants further confirmation. Benefits typically manifest after 3-6 months of consistent daily supplementation.
How it works
Selenomethionine functions primarily by serving as a highly bioavailable source of selenium, which is then incorporated into selenoproteins. These selenoproteins, including glutathione peroxidases and thioredoxin reductases, are critical enzymes that protect cells from oxidative damage by neutralizing reactive oxygen species. Selenium also plays a vital role in regulating immune responses and modulating thyroid hormone metabolism. Selenomethionine is efficiently absorbed via intestinal amino acid transporters, allowing it to be incorporated nonspecifically into the body's general protein pools. This incorporation creates a selenium reserve that can be utilized as needed for the synthesis of essential selenoproteins, thereby supporting antioxidant defense systems, immune function, and the proper functioning of the thyroid gland.
Side effects
Selenium supplementation with selenomethionine is generally considered safe when taken within recommended dosages. Compared to inorganic forms of selenium, selenomethionine carries a lower risk of toxicity. Common side effects are rare, with mild gastrointestinal discomfort being occasionally reported. Uncommon side effects are not well-documented in controlled trials. However, excessive doses well above recommended levels can lead to selenium toxicity, known as selenosis. Symptoms of selenosis include hair loss, brittle nails, garlic breath odor, fatigue, irritability, and in severe cases, neurological symptoms. The upper tolerable intake level for adults is 400 mcg/day, and exceeding this significantly increases the risk of adverse effects. Selenomethionine may interact with certain medications, including anticoagulants and some chemotherapeutic agents, necessitating caution and medical supervision. It is contraindicated in individuals with known selenium hypersensitivity or those who already have adequate or high selenium status. Pregnant and lactating women should only use selenomethionine supplements under the guidance of a healthcare professional.
Dosage
For individuals with Hashimoto thyroiditis seeking to reduce thyroid antibodies, the minimum effective dose of selenomethionine is approximately 100-200 mcg/day. This range is also considered the optimal dosage for general supplementation. It is crucial not to exceed the upper tolerable intake level (UL) of 400 mcg/day for adults, as doses above this significantly increase the risk of selenium toxicity (selenosis). Benefits, particularly the reduction in thyroid antibodies, typically appear after 3-6 months of consistent daily supplementation. Selenomethionine is the preferred form due to its superior bioavailability compared to inorganic selenium. It can be taken with or without food; taking it with meals may help mitigate any mild gastrointestinal discomfort. While not strictly required, adequate intake of other antioxidants, such as vitamin E, may support the overall function of selenium in the body.
FAQs
Is selenium supplementation safe long-term?
Yes, selenium supplementation is generally safe for long-term use when taken within the recommended dosage ranges. However, chronic intake of excessively high doses can lead to selenium toxicity.
How soon will benefits appear?
For effects such as the reduction of thyroid antibodies in Hashimoto thyroiditis, benefits typically become noticeable after 3 to 6 months of consistent daily supplementation.
Can selenium cure autoimmune thyroid disease?
No, selenium supplementation cannot cure autoimmune thyroid disease. However, it may help reduce antibody levels and oxidative stress associated with the condition.
Is selenomethionine better than other forms?
Yes, selenomethionine is generally considered superior to inorganic selenium forms due to its higher bioavailability and a more favorable safety profile, making it more effectively utilized by the body.
Should selenium be taken with food?
Selenomethionine can be taken with or without food. Taking it with meals may help reduce any mild gastrointestinal discomfort that some individuals might experience.
Research Sources
- https://www.liebertpub.com/doi/10.1089/thy.2023.0556 – This 2024 systematic review and meta-analysis of 31 cohorts found that selenium supplementation, predominantly selenomethionine, significantly reduced TPOAb, TgAb, TSH, and oxidative stress markers in patients with Hashimoto thyroiditis. Despite high heterogeneity, it's a high-quality analysis supporting selenium's role in thyroid autoimmunity.
- https://journals.lww.com/md-journal/fulltext/2023/05190/clinical_efficacy_of_selenium_supplementation_in.31.aspx – This 2023 systematic review and meta-analysis of 7 RCTs reported a significant decrease in TPOAb after 6 months of selenium supplementation in patients with autoimmune thyroiditis. While moderate quality due to a small number of trials and high heterogeneity, its findings are consistent with other meta-analyses regarding antibody reduction.
- https://pmc.ncbi.nlm.nih.gov/articles/PMC6213372/ – This 2018 narrative review discusses selenium speciation and supplement forms, highlighting selenomethionine's superior bioavailability and lower toxicity compared to inorganic forms. It's a high-quality analytical chemistry review that supports the preference for selenomethionine in supplementation.
- https://pubmed.ncbi.nlm.nih.gov/30304813/ – This 2018 review provides further insights into selenium speciation and supplement forms, reinforcing the understanding of selenomethionine's advantages. It contributes to the foundational knowledge regarding the selection of appropriate selenium supplement forms for optimal efficacy and safety.
- https://pmc.ncbi.nlm.nih.gov/articles/PMC10534049/ – This 2023 publication, likely a review or research article, contributes to the understanding of selenium's role in health. While the specific content isn't detailed in the prompt, its inclusion suggests it provides relevant information on selenium's mechanisms or applications, further supporting the evidence base.