Form Comparison

Selenomethionine vs Sodium Selenate

How selenomethionine and sodium selenate differ in potency, absorption, tolerance, and cost.

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Quick verdict. Selenate is almost completely absorbed, but much of it is lost in urine; selenomethionine is absorbed at over 90% and retained in body proteins. That retention raises blood selenium more and also means excess accumulates, so stay under the 400 mcg UL from all sources. Choose selenomethionine for standalone supplementation; selenate has no advantage outside a multivitamin.

Side by Side

Selenomethionine Sodium Selenate
Elemental content Varies by product 41.8% elemental selenium
Absorption High High
How it is absorbed Absorbed like methionine, more than 90%. Nonspecifically incorporated into body proteins in place of methionine, which creates a storage pool and higher blood selenium. Inorganic form; nearly completely absorbed, but a large share is excreted in urine rather than retained.
Typical dose 55-200 mcg daily 55-200 mcg daily
Common uses general supplementation, thyroid autoimmunity (mixed evidence) multivitamins, food fortification
Side effects Selenosis above the 400 mcg UL: garlic breath, hair and nail loss, GI upset. As for other forms at excess doses.
Cost Low Low
Also called L-selenomethionine selenate
Labels in index 237 13

When to Choose Selenomethionine

Choose selenomethionine when you want the best-retained form. The form used in the SELECT trial, which found no cancer prevention benefit at 200 mcg/day.

Selenomethionine

Well absorbed and the form used in SELECT. It builds up in body protein, which helps repletion and makes chronic overuse more consequential.

What to look for: 50-100 mcg per serving, counting any multivitamin, and only when diet or region suggests low status.

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When to Choose Sodium Selenate

Choose sodium selenate when it comes in a multivitamin. It has no standalone advantage. High absorption but poorer retention than organic forms.

Sodium Selenate

Choose sodium selenate when it comes in a multivitamin. It has no standalone advantage.

What to look for: Sodium Selenate named on the Supplement Facts panel, with the amount per serving stated.

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Products on Titrate

In Titrate's index of NIH label data, 237 labels named as selenium products list selenomethionine and 13 list sodium selenate.

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Selenium does not have its own search category yet. Each product above links to its full label in the NIH database.

Related

References

NIH Office of Dietary Supplements. Selenium: Fact Sheet for Health Professionals.

Clark LC, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. JAMA. 1996;276(24):1957-1963.

Stranges S, et al. Effects of long-term selenium supplementation on the incidence of type 2 diabetes: a randomized trial. Ann Intern Med. 2007;147(4):217-223.

Thomson CD, et al. Brazil nuts: an effective way to improve selenium status. Am J Clin Nutr. 2008;87(2):379-384.

Lippman SM, et al. 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.

Hurst R, et al. Establishing optimal selenium status: results of a randomized, double-blind, placebo-controlled trial. Am J Clin Nutr. 2010;91(4):923-931.

MacFarquhar JK, et al. Acute selenium toxicity associated with a dietary supplement. Arch Intern Med. 2010;170(3):256-261.

Marcocci C, et al. Selenium and the course of mild Graves' orbitopathy. N Engl J Med. 2011;364(20):1920-1931.