Selen – små mängder, olika former och gränser för forskningen

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Selected whole synthesis paragraphs; no linked trial originals assigned.

URL: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/
Title: Selenium — Fact Sheet for Health Professionals
Source updated: September 4, 2025
Capture: Explicitly selected whole paragraphs from the official NIH ODS web reader on 2026-10-18. Citation links represented by their displayed numeric labels. This is not the entire fact sheet, bibliography, original SELECT trial or original Cochrane review. Web-reader HTTP status not captured. No direct HTTP request made for this page.

Introduction — both complete paragraphs

Selenium is an essential mineral that is naturally present in many foods and added to others. It is also available as a dietary supplement. Selenium is a constituent of 25 selenoproteins, including thioredoxin reductases, glutathione peroxidases, and selenoprotein P [1]. Selenoproteins play critical roles in thyroid hormone metabolism, DNA synthesis, reproduction, and protection from oxidative damage and infection [2-4].

Soil and ground water contain inorganic forms of selenium (e.g., selenites, selenates) that plants accumulate and convert to organic forms, mostly selenomethionine and selenocysteine and their methylated derivatives. In foods, selenium is present primarily as selenomethionine along with selenocysteine. Dietary selenium is readily absorbed by the body, and absorption is largely not affected by selenium status [4-6].

Assessing selenium status — complete final paragraph on supplementation and biomarkers

In addition, research suggests that selenium supplementation does not increase selenoprotein P concentration and glutathione peroxidase activity unless individuals are selenium deficient [3,4,6,9,11,12]. Urinary methylated selenometabolites are not reliable selenium status biomarkers because many people lack the methylation enzymes due to genetic polymorphisms [4].

Food — complete opening summary

Foods that are high in protein, such as seafood, meat, and poultry, are rich sources of selenium. Brazil nuts contain particularly high amounts of selenium. The selenium concentrations of plant-based foods vary by geographic location because the amount and form of selenium in the soil and other factors can influence the selenium content of these foods.

Dietary Supplements — complete subsection

Forms of selenium that are commonly found in dietary supplements include selenomethionine, selenium-enriched yeast, sodium selenite, and sodium selenate. The body is able to absorb up to about 90% of the selenium from these forms.

Selenium is available in multivitamin/mineral supplements, in supplements that contain vitamin E and other ingredients, and as stand-alone supplements. Common forms include selenomethionine, selenium-enriched yeast (grown in a high-selenium medium, predominantly as selenomethionine), sodium selenite, and sodium selenate [21-23]. The doses of selenium in multivitamin/mineral supplements vary, but many contain 55 mcg. The amount of selenium is often higher in supplements with fewer ingredients.

For example, supplements that combine selenium with vitamin E or other ingredients generally contain 50 to 200 mcg of selenium. Selenium-only supplements typically contain 100 to 400 mcg [21].

The human body absorbs up to about 90% of selenium from selenomethionine, selenium-enriched yeast, selenite, and selenate [4-6,9,12,24].

Cancer — complete two opening summary paragraphs and selected complete early-trial, SELECT and Cochrane paragraphs

Some epidemiological studies have suggested that people with higher selenium status have a lower risk of several types of cancer, and one randomized controlled trial reported that men who took selenium had a lower risk of prostate cancer over a multi-year follow-up period. However, subsequent randomized controlled trials have found that selenium supplementation does not reduce the risk of prostate cancer or other forms of cancer.

More research is needed to characterize the relationship between selenium supplementation and cancer risk.

The Nutritional Prevention of Cancer Trial, which began recruitment in 1983, was a randomized controlled trial that investigated 200 mcg/day selenium as selenium yeast or placebo for a mean of 4.5 years in 1,312 men and women in the United States with histories of nonmelanoma skin cancer [60,61].

Although selenium supplementation did not reduce the recurrence of nonmelanoma skin cancer, a secondary analysis of the trial found that men who took selenium had a 49% lower risk of prostate cancer than those who took placebo over a mean follow-up of about 7.5 years. The effect was strongest among men with the lowest baseline plasma selenium concentrations (below 10.6 mcg/dL), with no effect among men with plasma selenium concentrations greater than 12.3 mcg/dL.

The subsequent Selenium and Vitamin E Cancer Prevention Trial (SELECT), however, did not find that selenium supplementation reduced the risk of prostate cancer. This randomized controlled trial in 35,533 men age 50 years or older from the United States, Canada, and Puerto Rico was discontinued after 5.5 years when analyses showed no association between prostate cancer risk and supplementation with 200 mcg/day selenium as selenomethionine with or without 400 international units (IU)/day vitamin E [62].

An additional 1.5 years of follow-up data on participants after they stopped taking the study supplements confirmed the lack of a significant association between selenium supplementation and prostate cancer risk [63]. Further investigation in a case-cohort of 1,739 men with prostate cancer and 3,117 matched controls from the SELECT trial found that selenium supplementation did not affect prostate cancer risk in men with low baseline selenium status (based on toenail selenium levels) [64].

However, the researchers did find an increased risk of high-grade prostate cancer in men with higher baseline selenium status (≥60th percentile of toenail selenium) and recommended that men over age 55 avoid selenium supplementation at doses that exceed recommended dietary intakes.

A 2018 Cochrane Review on the use of selenium for the prevention of cancer included 83 studies (including the studies described above) [59]. Among the 70 observational cohort studies reviewed, participants with the highest baseline selenium status had a 28% lower cancer risk and a 24% lower cancer mortality than those with the lowest status.

In addition, these participants had a 33% lower risk of bladder cancer; an 18% lower risk of lung cancer; an 18% lower risk of colorectal cancer; and, in men, a 16% lower risk of prostate cancer. The authors found no association between selenium status in women and the risk of breast cancer. However, due to major weaknesses in study design, confounders, and limitations in the assessment of selenium exposure, the certainty of evidence for these findings was very low.

In addition, no evidence of a dose-response relationship between selenium status and cancer risk was observed.

The 10 randomized, placebo-controlled trials examined in the 2018 Cochrane Review included a total of 27,232 participants, 94% of which were men [59]. Results from these studies showed that supplementing with 200 to 500 mcg/day selenium, primarily as selenomethionine, for 2 to 10.3 years had little to no effect on cancer incidence or mortality. The certainty of evidence was high for prostate, colorectal, lung, and bladder cancers and moderate for breast and nonmelanoma skin cancers.

Because most of the studies used 200 mcg/day selenium, the authors concluded that 200 mcg/day selenium does not reduce the overall risk of cancer or the risk of individual cancer types. They also concluded that more research is needed to determine if selenium supplementation might modify cancer risk in individuals with specific genetic backgrounds or nutritional status or if different forms of selenium have different effects [10,59].

Health Risks from Excessive Selenium — complete opening summary and following four paragraphs before the US UL table; complete two EFSA paragraphs after the table

Selenosis is the result of chronically high intakes of selenium. It is most commonly characterized by hair loss and nail brittleness or loss, but other signs and symptoms can include a garlic odor in the breath, a metallic taste in the mouth, skin rash, nausea, diarrhea, fatigue, irritability, and nervous system abnormalities. The Tolerable Upper Intake Level for selenium is 400 mcg for adults, and it ranges from 45 mcg to 400 mcg for infants, children, and adolescents, depending on age.

Chronically high intakes of the organic and inorganic forms of selenium have similar effects [13]. Early indicators of excess intake are a garlic odor in the breath and a metallic taste in the mouth. The most common clinical signs of chronically high selenium intakes, or selenosis, are hair loss and nail brittleness or loss. Other signs and symptoms include skin rash, nausea, diarrhea, fatigue, irritability, and nervous system abnormalities [3,13,62].

As discussed earlier, Brazil nuts contain very high amounts of selenium (68–91 mcg per nut) and could cause selenium toxicity if consumed regularly. Acute selenium toxicity has resulted from the ingestion of misformulated over-the-counter products that contain very large amounts of selenium [8,55]. In 2008, for example, 201 people experienced severe adverse reactions from taking a liquid dietary supplement that contained 200 times the labeled amount of selenium [116].

Acute selenium toxicity can cause severe gastrointestinal and neurological symptoms; acute respiratory distress syndrome; myocardial infarction; hair loss; muscle tenderness; tremors; lightheadedness; facial flushing; kidney failure; cardiac failure; and, in rare cases, death [13,55].

The FNB has established ULs for selenium from food and supplements based on the amounts of selenium that are associated with hair and nail brittleness and loss (see Table 3) [13]. These ULs, however, do not apply to people who are taking selenium under the care of a physician.

In 2023, the Panel on Nutrition, Novel Foods and Food Allergens of the European Food Safety Authority released a scientific opinion on the ULs for selenium [117].

Based on systematic reviews that examined associations between excess selenium intake and clinical effects, specifically alopecia, the panel set an upper limit for selenium of 255 mcg/day for all adults, including women who are pregnant or lactating, with lower amounts ranging from 70 to 230 mcg/day for children and teens, depending on age.

Interactions with Medications — complete opening summary and following paragraph

Selenium supplements may interact with medications. In addition, certain medications, such as cisplatin, can affect selenium levels in the body.

Selenium can interact with certain medications, and some medications can have an adverse effect on selenium levels. One example is provided below. Individuals who are taking this and other medications on a regular basis should discuss their selenium status with their health care providers.

Updated: September 4, 2025

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Full current exact imported definitions of distinct identities; not an identity merge

{"id":"chebi-27568","version_id":"a7502af2-f81a-47cc-91ad-8ee144538f50","name":"selenium atom","definition":""}

{"id":"chebi-15075","version_id":"453ffa0d-1c98-4a4b-b958-f8865a8e07b9","name":"selenate","definition":"A divalent inorganic anion obtained by removal of both protons from selenic acid."}

{"id":"chebi-18212","version_id":"da2142b8-9fa9-4f71-bf06-ec51c9b2152f","name":"selenite(2-)","definition":""}

{"id":"chebi-30021","version_id":"7bef846b-80cd-4669-b961-1e27a13788cb","name":"L-selenomethionine","definition":"The <small>L</small>-enantiomer of selenomethionine."}

{"id":"chebi-62621","version_id":"f7b93c46-a989-426d-84c8-3384e1c81ebd","name":"L-selenomethionine zwitterion","definition":"An amino acid zwitterion obtained by transfer of a proton from the carboxy to the amino group of <small>L</small>-selenomethionine; major species at pH 7.3."}

{"id":"chebi-48843","version_id":"ecc7c488-608b-4bff-a5ae-c08b8751ba69","name":"disodium selenite","definition":"An inorganic sodium salt composed of sodium and selenite ions in a 2:1 ratio."}

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Läs produktdeklarationen på ActiQs

Koenzym Q10 (ubikinon), MCT-olja (kokosnöt, akaciagummi), vegetabilisk kapsel (pullulan), E-vitamin (d-alfa-tokoferolsuccinat), selen (selenmetionin).

Innehåll:	1 kapsel	DRI % *
Koenzym Q10	200 mg	
Selen	200 μg	363
Vitamin E	60 mg	500
MCT-olja	200 mg	

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Läs produktdeklarationen på ActiQs

Supplement Facts
Serving Size: 1 Tablet
Servings Per Container: 90
	Amount Per Serving	% Daily Value
Selenium (as fermented selenium glycine)	50 mcg	91%
Food & Herb Blend 
S. cerevisiae, organic spinach, organic ginger root, organic turmeric root, organic rosemary leaf, organic parsley leaf, organic oregano leaf, organic brown rice, organic broccoli, organic carrot, organic beetroot	345 mg	**
**% Daily Value (DV) not established

Microcrystalline cellulose, ferment media (rice protein, organic brown rice, autolyzed yeast extract, yeast [inactive]), stearic acid, silicon dioxide, hypromellose.
This product is made with food-paired fermented minerals.

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Läs produktdeklarationen på ActiQs

Supplement Facts
Serving Size: 1 Tablet
	Amount Per Serving	%Daily Value
Selenium (from high selenium yeast)	200 mcg	364%

Microcrystalline cellulose, dibasic calcium phosphate, stearic acid, silica, and magnesium stearate. 

Contains no dairy, egg, gluten, corn, soy or wheat. Contains no starch, salt, preservatives, or artificial color, flavor or fragrance.