Home Ingredients Selenium SeLECT® (L-Selenomethionine — Sabinsa)
AntioxidantThyroid Health

Selenium SeLECT® (L-Selenomethionine — Sabinsa)

Evidence Level
Limited
3 Clinical Trials
4 Documented Benefits
2/5 Evidence Score

Selenium SeLECT® is Sabinsa's branded L-selenomethionine: a single, defined organic selenium compound rather than a selenium yeast. In 2008 Sabinsa announced self-affirmed GRAS status (an independent expert panel's judgment, not an FDA review), and it says the USP selenomethionine monograph is based on this material. Sabinsa also says the National Cancer Institute used Selenium SeLECT in SELECT, the large cancer prevention trial of 200 µg/day of L-selenomethionine in 35,533 men, and the trial report lists Sabinsa among its suppliers. SELECT found no reduction in prostate or other cancers, a small rise in type 2 diabetes that was not statistically significant, and more hair loss and dermatitis with selenium. Selenium is an essential mineral used to build selenoproteins involved in thyroid hormone metabolism and antioxidant defense. In a 28-month study of selenomethionine in healthy adults, thyroid hormones barely changed.

Studied Dose 200 µg/day of selenium as L-selenomethionine in SELECT and in the 28-month thyroid hormone study. The adult RDA is 55 µg/day and total selenium from all sources should stay below the adult upper limit of 400 µg/day.
Active Compound L-selenomethionine, a single defined organic selenium compound (not a selenium yeast), sold by Sabinsa as Selenium SeLECT®.

Benefits

Supports antioxidant defenses

Selenium from L-selenomethionine is used to build glutathione peroxidases, enzymes that break down peroxides. In 120 adults with very low selenium intake, selenomethionine restored full plasma glutathione peroxidase activity at 37 µg/day, versus 66 µg/day for selenite. In selenium-replete men, extra selenomethionine raised blood selenium but had little effect on this enzyme.

Supported by Trial 3, Trial 1

Thyroid hormone metabolism

Selenium is needed for the deiodinase enzymes that activate thyroid hormone. In a small study without a placebo group, 28 healthy adults took 200 µg/day of selenomethionine for 28 months: T4 and TSH did not change, and T3 rose about 5 percent a year in men only, which the researchers judged clinically insignificant. The benefit lies in avoiding a shortfall, not in taking extra.

Supported by Trial 1

Helps maintain selenium status

L-selenomethionine is well absorbed and partly built into body proteins, so blood selenium rises with daily use: in the 28-month study, plasma selenium was about 60 percent higher in men and roughly double in women by 9 months. Most people in the United States already get enough selenium from food.

Supported by Trial 1, Trial 2

Supplies selenium for selenoproteins

Selenium is part of 25 selenoproteins, including glutathione peroxidases, thioredoxin reductases and selenoprotein P, which take part in thyroid hormone metabolism, DNA synthesis, reproduction and protection from oxidative damage. Selenomethionine supplies selenium for these proteins once the body breaks it down.

Supported by Trial 3, Trial 1

Mechanism of action

1

Incorporation into body proteins

L-selenomethionine is absorbed through the same transporters as methionine and can be non-specifically incorporated into body proteins in place of methionine, creating a tissue reservoir of selenium that is gradually released for selenoprotein synthesis.

2

Selenoprotein synthesis

Selenium released from selenomethionine is metabolized to selenide and incorporated as selenocysteine into selenoenzymes such as glutathione peroxidases and thioredoxin reductases, which drive antioxidant and redox-regulating activity.

3

Thyroid selenoenzyme support

Selenium supplies iodothyronine deiodinases that convert thyroxine (T4) to the active hormone T3, and glutathione peroxidases that protect thyroid tissue from peroxide generated during hormone synthesis, supporting normal thyroid metabolism.

4

Antioxidant redox cycling

Selenium-dependent glutathione peroxidases reduce hydrogen and lipid peroxides using glutathione, while thioredoxin reductases regenerate antioxidant systems, together helping protect cells and membranes from oxidative damage.

Clinical trials

1
Selenomethionine and thyroid hormones in healthy adults (no placebo group)
PubMed

Before-and-after study with no placebo group: 200 µg/day of selenomethionine for 28 months, with thyroid hormones measured for 4 months before and quarterly during supplementation (Combs et al. 2009, Am J Clin Nutr)

28 healthy adults.

By 9 months plasma selenium rose from 1.78 to 2.85 µmol/L in men and from 1.64 to 3.32 µmol/L in women. T4 and TSH did not change. T3 rose about 5 percent a year in men only, which the authors judged not clinically significant because TSH did not fall.

2
SELECT: L-selenomethionine 200 µg/day in 35,533 men
PubMed

Randomized, double-blind, placebo-controlled trial of selenium (200 µg/day from L-selenomethionine), vitamin E, both, or placebo; supplements were stopped at a planned interim analysis for lack of benefit after a median 5.5 years (Lippman et al. 2009, JAMA)

35,533 relatively healthy men aged 50 or older (African American men) or 55 or older (all others) in the United States, Canada and Puerto Rico.

Selenium did not reduce prostate cancer (hazard ratio 1.04, 99% CI 0.87 to 1.24) or any other prespecified cancer. Type 2 diabetes was slightly more common with selenium but not significantly (relative risk 1.07, 99% CI 0.94 to 1.22), and alopecia and mild dermatitis were more frequent. Sabinsa was among the suppliers of study agents, and Sabinsa states the selenium was Selenium SeLECT.

3
Selenomethionine versus selenite in low-selenium adults
PubMed

Randomized supplementation trial: placebo or up to 66 µg/day of selenium as selenomethionine or selenite for 20 weeks (Xia et al. 2005, Am J Clin Nutr)

120 adults in a low-selenium area of China with average intake of about 10 µg/day.

Full expression of plasma glutathione peroxidase was reached at 37 µg/day as selenomethionine and at 66 µg/day as selenite, so selenomethionine had nearly twice the bioavailability. Neither form fully expressed selenoprotein P at the doses tested.

Side effects and drug interactions

Common Potential side effects

L-selenomethionine is generally well tolerated at nutritional doses of 50-200 µg per day in adults, but long-term supplementation at the top of that range has been linked to type 2 diabetes. In the Nutritional Prevention of Cancer trial, 1,202 adults took 200 µg/day of selenium (as selenised yeast) or placebo for an average of 7.7 years, and diabetes developed in 58 people on selenium versus 39 on placebo: a hazard ratio of 1.55 (95% CI 1.03 to 2.33). The risk was concentrated in people whose baseline plasma selenium was already highest (hazard ratio 2.70, 95% CI 1.30 to 5.61 in the top third).
Intake above the 400 µg/day upper limit can cause selenosis and selenium toxicity over time.
Selenosis symptoms include hair loss, brittle or discolored nails, and a garlic-like breath odor.
Excess selenium may cause nausea, fatigue, irritability, skin rash, or a metallic taste.
Combine carefully with other selenium sources so total daily intake stays below the UL. The diabetes evidence is conflicting rather than settled: SELECT, a trial of L-selenomethionine (supplied by Sabinsa) at 200 µg/day in 35,533 men, found only a small increase in adult-onset diabetes that did not reach statistical significance (relative risk 1.07, 99% CI 0.94 to 1.22), and a 2014 meta-analysis of four randomised trials in 20,294 people pooled to a relative risk of 1.09 (95% CI 0.99 to 1.20). Even so, people with diabetes or prediabetes, and anyone whose selenium intake is already high, should talk to a doctor before taking 200 µg/day. SELECT also recorded more alopecia and dermatitis in the selenium group, and more high-grade prostate cancer among the men who began the trial with the highest selenium levels.

Important Drug interactions

Adds to selenium from multivitamins, yeast supplements, and fortified foods toward the UL.
Cisplatin: this chemotherapy drug can lower selenium levels in hair and serum, and whether that matters clinically is not known. People on chemotherapy or radiotherapy should ask their oncologist before taking selenium.
Thyroid medication: selenium takes part in thyroid hormone metabolism, so people treated for a thyroid condition should tell their doctor before starting it.

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Frequently asked questions about Selenium SeLECT® (L-Selenomethionine — Sabinsa)

What is Selenium SeLECT?

Selenium SeLECT® is Sabinsa's branded L-selenomethionine: a single, defined organic selenium compound rather than a selenium yeast. In 2008 Sabinsa announced self-affirmed GRAS status (an independent expert panel's judgment, not an FDA review), and it says the USP selenomethionine monograph is based on this material.

What is Selenium SeLECT used for?

Selenium SeLECT is researched primarily for Antioxidant and Thyroid Health. Selenium from L-selenomethionine is used to build glutathione peroxidases, enzymes that break down peroxides. In 120 adults with very low selenium intake, selenomethionine restored full plasma glutathione peroxidase activity at 37 µg/day, v…

What is the recommended dosage of Selenium SeLECT?

The clinically studied dose is 200 µg/day of selenium as L-selenomethionine in Select and in the 28-month thyroid hormone study. The adult RDA is 55 µg/day and total selenium from all sources should stay below the adult upper limit of 400 µg/day. Always follow the product label and check with a healthcare provider for personal advice.

Is Selenium SeLECT safe, and does it have side effects?

For most healthy adults, Selenium SeLECT is well tolerated at studied doses. Reported effects can include: L-selenomethionine is generally well tolerated at nutritional doses of 50-200 µg per day in adults, but long-term supplementation at the top of that range has been linked to type 2 diabetes. It may also interact with some medications. Selenium SeLECT is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Selenium SeLECT interact with any medications?

Possible interactions include: Adds to selenium from multivitamins, yeast supplements, and fortified foods toward the UL. Cisplatin: this chemotherapy drug can lower selenium levels in hair and serum, and whether that matters clinically is not known. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Selenium SeLECT?

NutraSmarts rates the evidence for Selenium SeLECT as Limited (2 out of 5). It is backed by 3 clinical trials and 10 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(10 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Combs GF Jr, Midthune DN, Patterson KY, Canfield WK, Hill AD, Levander OA, Taylor PR, Moler JE, Patterson BH. Effects of selenomethionine supplementation on selenium status and thyroid hormone concentrations in healthy adults. Am J Clin Nutr. 2009;89(6):1808-14. doi: 10.3945/ajcn.2008.27356.PubMedUsed to support: 28 healthy adults took 200 µg/day of selenomethionine for 28 months, with thyroid hormones measured for 4 months before supplementation and quarterly during it. By 9 months plasma selenium rose from 1.78 to 2.85 µmol/L in men and from 1.64 to 3.32 µmol/L in women. T4 and thyrotropin were unchanged, and T3 rose 5 percent per year in men only, which the authors judged clinically insignificant. There was no placebo group.
  2. Bügel S, Larsen EH, Sloth JJ, Flytlie K, Overvad K, Steenberg LC, Moesgaard S. Absorption, excretion, and retention of selenium from a high selenium yeast in men with a high intake of selenium. Food Nutr Res. 2008;52:1642. doi: 10.3402/fnr.v52i0.1642.PubMedUsed to support: In 12 healthy men already taking 300 µg/day of supplemental selenium, a single 327 µg tracer dose of selenium from selenium-enriched YEAST was 89 ± 4 percent absorbed and 74 ± 6 percent retained. Important form mismatch: this is a pharmacokinetic study of a selenium yeast, specifically the SelenoPrecise® yeast made by Pharma Nord, which is a different company's product and a mixture of many selenium species. Selenium SeLECT® is a single purified molecule and is not a yeast, so this study does not measure how this ingredient is absorbed.
  3. Lippman SM, Klein EA, Goodman PJ, Lucia MS, Thompson IM, Ford LG, Parnes HL, Minasian LM, Gaziano JM, Hartline JA, Parsons JK, Bearden JD 3rd, Crawford ED, Goodman GE, Claudio J, Winquist E, Cook ED, Karp DD, Walther P, Lieber MM, Kristal AR, Darke AK, Arnold KB, Ganz PA, Santella RM, Albanes D, Taylor PR, Probstfield JL, Jagpal TJ, Crowley JJ, Meyskens FL Jr, Baker LH, Coltman CA Jr. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2009;301(1):39-51. doi: 10.1001/jama.2008.864.PubMedUsed to support: In 35,533 relatively healthy men, 200 µg/day of selenium from L-selenomethionine did not reduce prostate cancer (hazard ratio 1.04, 99% CI 0.87 to 1.24) or other prespecified cancers, and supplements were stopped at a planned interim analysis for lack of benefit. Type 2 diabetes was slightly but not significantly more common with selenium (relative risk 1.07, 99% CI 0.94 to 1.22), and alopecia (relative risk 1.28) and grade 1 to 2 dermatitis (relative risk 1.17) were more frequent. The report lists Sabinsa Corporation among the suppliers of study agents.
  4. Stranges S, Marshall JR, Natarajan R, Donahue RP, Trevisan M, Combs GF, Cappuccio FP, Ceriello A, Reid ME. Effects of long-term selenium supplementation on the incidence of type 2 diabetes: a randomized trial. Ann Intern Med. 2007;147(4):217-23. doi: 10.7326/0003-4819-147-4-200708210-00175.PubMedUsed to support: In 1,202 adults given 200 µg/day of selenium (as selenised yeast) or placebo for an average of 7.7 years, type 2 diabetes developed in 58 selenium recipients and 39 placebo recipients (12.6 versus 8.4 cases per 1,000 person-years; hazard ratio 1.55, 95% CI 1.03 to 2.33). Risk rose across thirds of baseline plasma selenium and was highest in the top third (hazard ratio 2.70, 95% CI 1.30 to 5.61). Two limits matter: diabetes was a secondary outcome analysed after the fact, and the trial used selenised yeast rather than the single L-selenomethionine molecule sold here.
  5. Mao S, Zhang A, Huang S. Selenium supplementation and the risk of type 2 diabetes mellitus: a meta-analysis of randomized controlled trials. Endocrine. 2014;47(3):758-63. doi: 10.1007/s12020-014-0298-7.PubMedUsed to support: Pooling four randomised controlled trials with 20,294 participants, selenium supplementation was associated with a relative risk for type 2 diabetes of 1.09 (95% CI 0.99 to 1.20, p = 0.085) versus control: a small increase that did not reach statistical significance. Dropping any single trial did not change the estimate. This is the reason the diabetes question should be described as unresolved rather than as proven harm.
  6. Xia Y, Hill KE, Byrne DW, Xu J, Burk RF. Effectiveness of selenium supplements in a low-selenium area of China. Am J Clin Nutr. 2005;81(4):829-34. doi: 10.1093/ajcn/81.4.829.PubMedUsed to support: 120 adults with an average selenium intake of about 10 µg/day were randomly assigned to placebo or up to 66 µg of selenium per day, as selenomethionine or as selenite, for 20 weeks. Plasma glutathione peroxidase was fully expressed at 37 µg/day as selenomethionine but needed 66 µg/day as selenite, so selenomethionine had nearly twice the bioavailability. Neither form fully expressed selenoprotein P. The participants were severely selenium-deficient, and the outcomes are blood selenoprotein markers, not clinical outcomes.
  7. Vinceti M, Filippini T, Del Giovane C, Dennert G, Zwahlen M, Brinkman M, Zeegers MP, Horneber M, D'Amico R, Crespi CM. Selenium for preventing cancer. Cochrane Database Syst Rev. 2018;1(1):CD005195. doi: 10.1002/14651858.CD005195.pub4.PubMedUsed to support: A Cochrane review of 83 studies, including 10 randomised trials in 27,232 people. Across the trials at low risk of bias, selenium supplementation did not change overall cancer incidence (risk ratio 1.01, 95% CI 0.93 to 1.10; 3 studies, 19,475 participants; high-certainty evidence), and it did not reduce prostate, lung, colorectal, bladder or skin cancer. On harms, the randomised trials showed a slightly increased risk of type 2 diabetes and, in the trials at low risk of bias, a suggestion of increased melanoma risk; the largest trial recorded more alopecia and dermatitis in the selenium group, and men who began with the highest background selenium had a higher risk of high-grade prostate cancer. This is a systematic review, not a trial.
  8. Marshall JR, Burk RF, Payne Ondracek R, Hill KE, Perloff M, Davis W, Pili R, George S, Bergan R. Selenomethionine and methyl selenocysteine: multiple-dose pharmacokinetics in selenium-replete men. Oncotarget. 2017;8(16):26312-26322. doi: 10.18632/oncotarget.15460.PubMedUsed to support: 29 selenium-replete men were randomized to selenomethionine or methylselenocysteine for 84 days. Selenomethionine raised blood selenium more than methylselenocysteine, but neither form had more than a minimal effect on selenoprotein P or glutathione peroxidase, and no toxicity was seen.
  9. Office of Dietary Supplements, National Institutes of Health. Selenium: Fact Sheet for Health Professionals (updated September 4, 2025). NIH Office of Dietary Supplements. 2025;Not PubMed-indexed..SourceUsed to support: Official NIH fact sheet. States that selenium is part of 25 selenoproteins (including glutathione peroxidases, thioredoxin reductases and selenoprotein P) that take part in thyroid hormone metabolism, DNA synthesis, reproduction and protection from oxidative damage; that the adult RDA is 55 µg/day and the adult upper limit 400 µg/day; that early signs of excess are garlic breath and a metallic taste, and chronic excess (selenosis) causes hair loss and brittle or lost nails, rash, nausea, diarrhea, fatigue, irritability and nervous system problems; that most people in the United States get enough selenium; and that cisplatin can lower selenium levels in hair and serum, with unknown clinical significance. Not PubMed-indexed.
  10. Heller L. Sabinsa selenium gets GRAS (April 1, 2008). NutraIngredients. 2008;Not PubMed-indexed..SourceUsed to support: Trade news report of a Sabinsa announcement. States that Selenium SeLECT received self-affirmed GRAS status after an independent panel of scientists reviewed its safety and toxicology data, that the USP monograph for selenomethionine is based on Sabinsa's ingredient, and that the National Cancer Institute was using Selenium SeLECT in a 12-year study of selenium and vitamin E for prostate cancer prevention and in a trial on age-related memory loss. These are company statements; the SELECT report itself lists Sabinsa Corporation among the suppliers of study agents. Not PubMed-indexed.