What Selenium Is
Selenium is an essential trace mineral, needed in micrograms rather than milligrams. It sits inside selenoproteins, including the enzymes that convert thyroid hormone into its active form and the glutathione peroxidases that do antioxidant work. Remedy's Selenium supplies 200 mcg per vegan capsule, with 60 capsules per bottle.
It is one of the most heavily trialled supplements on these shelves, and it is also one of the few with a ceiling close enough to matter.
-
200 mcg per capsule: The amount used in most clinical trials.
-
60 capsules: Two months at 1 daily.
-
Adult RDA: 55 mcg per day.
-
Tolerable upper limit: 400 mcg per day.
The full evidence map is in our selenium overview.
Supplement Facts
Serving size: 1 Vegan Capsule. Servings per container: 60.
| Amount Per Serving |
Amount |
% Daily Value |
| Selenium |
200 mcg |
364% |
Other ingredients: Cellulose, Glycerin, Water (vegan capsule)
Directions: One capsule daily, with food.
Made in the USA.
The Narrow Window
This is the fact that should shape how you treat selenium, and it separates this mineral from almost everything else in the shop.
| Amount of selenium per day |
What it represents |
| 55 mcg |
The adult recommended dietary allowance |
| 200 mcg |
The amount used in most trials, and our capsule |
| 400 mcg |
The tolerable upper intake level for adults |
| Above 400 mcg |
Where selenosis becomes the concern |
| A few Brazil nuts |
Can span that whole range on their own |
The gap between the recommended intake and the ceiling is roughly 7-fold. For most water-soluble vitamins there is no meaningful ceiling at all, which is why counting every source matters here. The detail is in selenium dosage and the upper limit.
What the Evidence Actually Shows
Rather than print a benefits list, we would rather print the shape of the literature. These counts came off PubMed and anyone can rerun them.
| What PubMed holds on selenium supplementation |
Count |
| Records on selenium supplementation |
5,811 |
| Records tagged as human |
2,593 |
| Randomized or clinical trials |
1,289 |
| Systematic reviews or meta-analyses |
539 |
| Human records mentioning selenosis or toxicity |
1,257 |
Selenium is not short of evidence. It is short of agreement, and the two clearest examples are worth knowing before you buy.
What SELECT Found
For two decades selenium was sold on cancer prevention. A randomized trial tested that directly.
-
Design: Randomized and placebo-controlled, in relatively healthy men.
-
Arms: Selenium, vitamin E, both, or neither.
-
Result: No reduction in prostate cancer risk from either.
-
Also found: A statistically nonsignificant increase with vitamin E.
The 2009 report is unambiguous on the selenium arm.[1]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) View source Longer follow-up in 2011 examined the vitamin E signal further.[2]Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT) — JAMA (2011) View source We do not sell selenium on a prevention claim, because that claim was tested and did not hold. The detail is in what the SELECT trial found.
The Thyroid Question
Selenium is genuinely required for thyroid hormone conversion, and the clinical evidence still disagrees with itself.
-
2017 review: Insufficient documentation for clinical efficacy.[3]Insufficient documentation for clinical efficacy of selenium supplementation in chronic autoimmune thyroiditis — Endocrine (2017) View source
-
2018 review: Autoantibody levels significantly reduced.[4]Selenium Supplementation Significantly Reduces Thyroid Autoantibody Levels in Patients with Chronic Autoimmune Thyroiditis — Thyroid (2018) View source
-
Same question: Chronic autoimmune thyroiditis, one year apart.
-
What differed: Which endpoints counted as clinically relevant.
Both are cited here because presenting either alone would be selective. The full comparison is in selenium and thyroid health.
Where It Comes From in Food
Selenium is unusual in that the amount in your food depends on the soil it grew in rather than on the food itself.
-
Richest source: Brazil nuts, and the most variable by far.
-
Other sources: Seafood, organ meats, eggs and cereals.
-
Why it varies: Plants take up whatever the soil holds.
-
Consequence: Deficiency is geographic rather than dietary.
Treat Brazil nuts as an unmeasured dose rather than a snack, because the same handful is not the same amount twice. More in selenium deficiency and food sources.
Safety and Who Should Be Careful
At ordinary intakes selenium is well tolerated. The concern is stacking sources past the ceiling.
| Situation |
Position |
| Already taking a multivitamin with selenium |
Count that first, then decide |
| Eating Brazil nuts most days |
You may already be at the RDA or beyond |
| Hair loss, brittle nails or garlic breath |
Stop and seek advice |
| Thyroid disease on levothyroxine |
Discuss before starting |
| Pregnant or breastfeeding |
The margin is smaller, so ask first |
Chronic excess causes selenosis, whose classic signs are hair loss, brittle nails and a garlic-like breath odour. A separate metabolic question was examined in a meta-analysis of randomized trials on type 2 diabetes risk.[5]Selenium supplementation and the risk of type 2 diabetes mellitus: a meta-analysis of randomized controlled trials — Endocrine (2015) View source Both are covered in selenium side effects and toxicity.
Why Choose Remedy's Selenium
No trial makes one selenium better than another, so the honest differentiators are the amount and what the page is willing to say.
-
200 mcg: The trialled amount, and half the upper limit.
-
Single ingredient: Selenium, with 0 other actives.
-
No prevention claim: Because SELECT tested it and found none.
-
The ceiling stated: 400 mcg, on the page rather than hidden.
The metabolic question is in selenium and diabetes risk.
Frequently Asked Questions
What does selenium do? +
It sits inside selenoproteins, including the enzymes that convert thyroid hormone to its active form. That is 1 specific job.
How much selenium is in a capsule? +
200 mcg, which is the amount most clinical trials used and half the 400 mcg upper limit.
How much selenium per day is safe? +
The tolerable upper intake level for adults is 400 mcg. The recommended intake is 55 mcg.
Does selenium prevent cancer? +
No. SELECT randomized healthy men and found 0 reduction in prostate cancer risk from selenium.
Is selenium good for the thyroid? +
The evidence disagrees. A 2017 review found insufficient documentation and a 2018 review found autoantibodies significantly reduced.
Can you take too much selenium? +
Yes, and the margin is narrow. Excess causes selenosis, whose 3 classic signs are hair loss, brittle nails and garlic breath.
Can I take this with a multivitamin? +
Check the multivitamin label first, because most contain selenium. Stacking 2 sources is how people exceed the limit.
How many Brazil nuts equal this? +
There is no fixed answer, because content varies with soil. A few nuts can span the whole 55 to 400 mcg range.
How long does 1 bottle last? +
Sixty capsules is 2 months at 1 capsule daily.
Should I take it with food? +
With food is the usual instruction. 0 trials have compared timings.
You May Also Like
