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Selenium
An essential trace mineral with six authorised EU health claims and a narrow margin between what you need and what is too much: the NRV is 55 µg a day and the EFSA upper limit is 255 µg. It sits in three of our formulas, so the engine counts it across your whole plan, never one formula at a time.
WHAT WE ARE ALLOWED TO SAY
Six claims. All of them authorised.
These are the six authorised wordings for selenium, translated from the Spanish text of the EU register: we have not yet checked them word for word against the English version, and we do not paraphrase them into something that sounds stronger. All six carry the same condition: the product has to be at least a source of selenium under Regulation (EC) 1924/2006. Our three formulas serve 55 to 200 µg, which is 100% to 364% of the NRV.Six authorised wordings, translated from the Spanish text of the EU register and not yet checked word for word against the English one. All six need the product to be at least a source of selenium. Our formulas serve 100% to 364% of the NRV.
None of the six is a claim about cancer, the heart, fertility or thyroid antibodies. The cancer studies we cite, the SELECT trial and a 2018 Cochrane review, found no benefit in trials, and our formula for raised thyroid antibodies follows a clinical study, not a claim: normal thyroid function is as far as the wording goes. Two of the six are about hair and nails, which is also the effect EFSA's upper limit is built on: hair loss and brittle nails are the key signs of too much selenium over time.
WHY SELENOMETHIONINE
The claims do not change. What your body does with it does.
The six claims attach to selenium, not to a particular form, so the form is not a claim argument and we do not use it as one. We chose L-selenomethionine: our notes record about 90% absorbed, and your body stores it in its own proteins, which gives a steadier effect. Our files also mark it as stable in liquid and neutral in taste, and high doses of vitamin C do not interfere with it.
Sodium selenite is cheaper, and our notes record about 50% absorbed. High doses of vitamin C turn it into a form that is absorbed less well. Acceptable at low doses; sodium selenate has the same limits and we avoid it.
Selenium-enriched yeast is a natural mix of selenomethionine, selenocysteine and selenoproteins. Our file records it as the form used in the SELECT and NPC trials, though elsewhere the same file describes SELECT as selenomethionine. It is on file as an alternative, not as what we chose.
The organic form, L-selenomethionine. About 90% absorbed in our notes, and stored in your body's proteins in place of methionine, which is why its effect is steady and also why it builds up.
Better absorption is what our notes record, not an authorised claim, so you will not read it on a label. Being stored in protein cuts both ways: our files put its half-life in your body at months, not days, so it accumulates. There are two open points we would rather write down: the Immunity formula does not specify a form of selenium yet, and whether the batch we buy is listed under Regulation (EC) 1170/2009 is still to be confirmed.Better absorption is not an authorised claim. Selenomethionine stays in your body for months, so it accumulates. And the Immunity formula does not specify a form yet.
WHERE IT APPEARS
Three of the twenty-nine carry selenium.
One is a CORE formula, assigned from the questionnaire; the other two are blood-test formulas for the thyroid, and the one for thyroid antibodies is still in development. All three serve it in the morning. They are never stacked freely: the engine adds up selenium across your plan, and Autoimmune thyroid does not run next to either of the others. One point on Immunity we would rather write down: the echinacea it also carries, 600 mg, is limited to 10 continuous days by the EMA monograph, while the formula is meant for daily use. Our file says it has to be reformulated, with echinacea removed or the formula taken in 8 to 10-day cycles, and that it should stay under review until then.
THE CEILING
255 µg a day, and your diet counts.
EFSA revised its upper limit for selenium in 2023, from 300 µg down to 255 µg a day for adults. It is built on hair loss, the effect EFSA chose as its reference point, seen at 330 µg a day in the SELECT trial. Our file puts an average Spanish diet at 60 to 90 µg, which is why the engine adds up selenium across your whole plan instead of checking each formula on its own.The limit covers your total, and our file puts an average Spanish diet at 60 to 90 µg. That is why the engine adds up selenium across your whole plan.
Our file sets no more than 100 µg per dose and 200 µg a day across all VION formulas, and the engine blocks any formula that would take your total to the EFSA limit. Autoimmune thyroid serves 200 µg in a single dose, above our own 100 µg-per-dose rule; our file has not reconciled the two, and the formula is still in development. Its own file notes that the EFSA limit only leaves room for a short course at 200 µg, so it runs six months, pauses 90 days, runs no more than twice a year and stops if there is no response after 12 months. Germany's BfR suggests 45 µg a day for a supplement, and all three of our doses are above it; France's ANSES works to 300 µg, diet included. Our file also notes that most EU supplements cap selenium at 200 µg a day, and that Spanish and French general-purpose products tend to stay at 80–100 µg: Autoimmune thyroid, at 200 µg, sits at that EU cap on its own and above the Spanish and French range, and Functional thyroid, at 100 µg, sits at the top of it.
Early signs are garlic breath, a metallic taste, tiredness, irritability and nausea. Over time the key signs are hair loss and brittle or lost nails, the effect EFSA's limit is built on. Beyond that come skin rash, joint pain, nerve damage in the hands and feet, changes to tooth enamel and liver damage. Our file records endemic selenosis in Enshi, China, from diets bringing 3,000 to 6,700 µg a day.
Contraindicated if you have or have had selenium toxicity (selenosis), if your blood selenium is high (above 122 µg/L) with no clinical reason, or if you are hypersensitive to it. With type 2 diabetes, take care: the SELECT and NPC trials suggest a higher risk in people who already have high selenium, so avoid it if yours is high. In pregnancy and breastfeeding it is safe at dietary amounts (60–70 µg), but do not take high doses: our file keeps pregnancy to diet and a basic multivitamin, the American Thyroid Association advises against routine selenium in pregnant women with thyroid autoimmunity, and both thyroid formulas are ruled out in pregnancy and in overt hyperthyroidism, Functional thyroid also with thyroid nodules still being investigated. Stop and see a doctor if you notice yellowing skin or eyes, unusual tiredness, abdominal pain or dark urine, and ask first if you have liver disease; none of the three formulas that carry it is given with liver disease or with vitamin K antagonist anticoagulants, and Immunity is also ruled out if you have an autoimmune condition or are on immunosuppressants. With cancer, avoid high doses, especially men who already have high selenium, and ask your oncologist first if you are in treatment. Under 18, only with a medical indication; the US limits run from 90 to 400 µg a day by age. Our file lists no specific contraindication for kidney disease, heart disease or psychiatric medication, and it contains none of the fourteen allergens that must be declared in the EU.
WHAT IT REACTS WITH
Documented pairs, not hunches.
Selenium is one of the 140 ingredients in our library, so it has 139 possible partners. We have documented 13 of them, out of the 443 pairs on file. Six are partners that can share a dose: zinc at standard doses (our file documents the pair up to 15 mg of zinc with 100 µg of selenium; Autoimmune thyroid sits above that, with 200 µg of selenium next to 15 mg of zinc, and is still in development), coenzyme Q10, manganese, L-cysteine, NAC and sulforaphane. Our file recommends the coenzyme Q10 pair for heart-focused healthy-ageing profiles from 60, on the basis of a Swedish trial in older adults.
Activated charcoal adsorbs and partly binds selenium, so the two never share a dose and stay at least 3 hours apart. White clay binds it, and konjac glucomannan and psyllium husk trap it in their gel, so all three are kept at least 2 hours away. Vitamin C only matters for selenite, which is kept 2 hours from vitamin C doses above 500 mg; with selenomethionine, the form we use, there is no restriction.
In smokers, beta-carotene taken with vitamin E and selenium has been linked to a higher risk of lung cancer in the CARET, ATBC and SELECT trials. If you smoke, or stopped less than 10 years ago, the engine blocks beta-carotene above 5 mg next to selenium or high-dose vitamin E, and uses lutein and zeaxanthin instead. Otherwise, selenium and vitamin E can share a dose at nutritional amounts.
None of these is in our medication matrix yet; they come from our ingredient file. Selenium can change the effect of anticoagulants such as warfarin, acenocoumarol, apixaban and dabigatran: ask your doctor first, and have your INR checked if you start or stop it. With cancer treatment, including platinum chemotherapy such as cisplatin, ask your oncologist first. Keep it at least 4 hours from levothyroxine as a precaution, and our notes flag a possible effect with methimazole. Our file also lists statins, niacin taken with statins, immunosuppressants, oral contraceptives, which can lower blood selenium slightly, and lithium, where hair loss can add up. If you take any of them, ask your doctor before starting.
443 of the 9,730 possible pairs in our library are documented, which is 4.55%. The rest are not "safe", they are simply unchecked, and we would rather write that down than let the number look like a badge.443 of the 9,730 possible pairs in our library are documented, which is 4.55%. The rest are not safe, they are simply unchecked, and we would rather write that down than let the number look like a badge.
SOURCES
Everything on this page, with its reference.
Reviewed by VION nutrition team · last reviewed 16 September 2026Read the introduction to Sodium selenite →
140 INGREDIENTS · 64 IN USE TODAY
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What it is, what we are allowed to say about it, which formulas carry it, what it reacts with and where each of those statements comes from. No proprietary blends, no hidden amounts.