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    Created in 2008, Phoenix Rising is the largest and oldest forum dedicated to furthering the understanding of, and finding treatments for, complex chronic illnesses such as chronic fatigue syndrome (ME/CFS), fibromyalgia, long COVID, postural orthostatic tachycardia syndrome (POTS), mast cell activation syndrome (MCAS), and allied diseases.

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High-Dose Selenium Significantly Improves My Fatigue and Brain Fog

Does selenium 400 mcg daily help your CFS? Have an active enterovirus infection, tested at ARUP Lab?

  • Selenium HELPED. My ARUP Lab tests showed I HAVE an active enterovirus infection

    Votes: 4 6.7%
  • Selenium HELPED. My ARUP Lab tests showed I DO NOT HAVE an active enterovirus infection

    Votes: 3 5.0%
  • Selenium DID NOT HELP. My ARUP Lab tests showed I HAVE an active enterovirus infection

    Votes: 1 1.7%
  • Selenium DID NOT HELP. My ARUP Lab tests showed I DO NOT HAVE an active enterovirus infection

    Votes: 1 1.7%
  • Selenium MADE ME FEEL WORSE (or made me feel too mentally "wired" and over-stimulated)

    Votes: 7 11.7%
  • Selenium HELPED. I have not been tested for enterovirus at ARUP Lab

    Votes: 27 45.0%
  • Selenium DID NOT HELP. I have not been tested for enterovirus at ARUP Lab

    Votes: 17 28.3%

  • Total voters

Rufous McKinney

Senior Member
However, I can't take it that long as it seems to cause brain swelling/neck stiffness/dizziness+additional brain fog which lasts many months to recover.

Anyone else experiencing this?

I would assume these are detox effects. As soon as the detox gets too intense I give up and stop whatever it is I am doing.

To get to the other side, is the great Goal and mystery. (Zeolite, is still waiting for me on a shelf) (lymph cleanse herbal tea) (All Thiamine Cure with charcoal bottles not opened) (the Copaiba experiment I'm still engaged in...)

Rufous McKinney

Senior Member
I find distinguishing between detox or herx or just plain 'bad reaction' quite challenging.

yes...it is hard...

sometimes I taste metal in my mouth and decide: DETOX

that happens when I do my lymph cleanse herbs...or the proteolytic enzymes. Or my recent self poisoning, in which I took a very hot bath every four hours for four days, and released a toxic metal load of vast proportion it would seem.

Or all the what ever else it is...

especially if it takes months to recover when it's stopped?

You'd think..it isn't months..but I just don't know.

if its truly antiviral, maybe we just take so long to gradually kill them off too? or is it the "no longer alive" remnants of their former selves, making us sick (the ghost of viruses past)


Senior Member
I found selenium raises vitamin D levels. I can't prove this because I don't have any tests done, but it happened twice. I got fatigue, headache and foamy urine for months, because it was D overdose. Used lots of vitamin E before that so I think selenium have been absorbed too good and taking vitamin D especially in one day with selenium raised D levels too much. Acu-cell website says vitamin E is vitamin D synergist.

I also found that selenium was SUPER helpful when I couldn't normally breathe during covid. It helped immediately. Maybe the reason of deaths is so simple, if so this is frustrating.


Senior Member
I found selenium raises vitamin D levels. I can't prove this because I don't have any tests done, but it happened twice. I got fatigue, headache and foamy urine for months, because it was D overdose.

Thanks for this information, but it doesn't seem the case for me. Indeed, vitamin D supplementation seem to attenuate the effects of selenium mildly, at least for me.


Senior Member
@kewia selenium also should be taken with iodine for proper balance for thyroid function. Iodine deficiency in me definitely felt like something in neck bothering me (thyroid). But be careful with iodine, it's dangerous supplement, there're protocols with iodine where vitamin C, b2 and b3 should be taken together with iodine so there's no creepy detox symptoms. And I don't recommend high dose iodine protocols for starters


Senior Member
@kewia Another reason of your symptoms could be mercury detox induced by selenium which creates brain fog. I heard iodine involved in mercury detox too, so iodine may be a solution. But again, if you decide to try, be careful. I needed high doses of vit C to not crash on iodine and vit C induced another detox in me. Tho it's not common for relatively healthy people


Senior Member
Iodine at 2 mg Lugol's drops was one of the worst decisions of my life -- threw me into thyroid crisis 8 years ago and I've never recovered. Made my ME/CFS much worse, major weight gain. Was taking Selenium, magnes at the time. Tried selenium again recently and made me feel druged.

Edit - however the selenium was in the suboptimal form of selenomethionine and had mag stearate so maybe that contributed to my recent drugged feeling, who knows. But regardless, the iodine was really bad news for me.

Anyone know why iodine would cause such a severe reaction? I've met several other ppl who react this way.
Last edited:


Senior Member
Brisbane, Australia
However, I can't take it that long as it seems to cause brain swelling/neck stiffness/dizziness+additional brain fog which lasts many months to recover.
Sounds like a sign of selenium poisoning!

sometimes I taste metal in my mouth and decide: DETOX
Metallic taste in mouth is a sign of selenium poisoning!

Please be careful, Selenium is toxic in high amounts. There is no antidote for selenium poisoning.
Make sure you know the Symptoms Of Selenium Poisoning In Humans.


Senior Member
Just to give my two cents here:

I can't take iodine as well to selenium and I didn't need to take selenium in high doses to get that behavior, rather how long you go with supplementation is important.

I think my reaction don't stem from selenosis, but selenium seem to activate MCAS in me, with recurrent anaphylactic shocks triggered by day patterns or by temperature.

I can't take supplements yet that I tolerated before without problems.
But it seems to improve over time, suffering months from it is probably a result of the long half-time of selenium in tissue.
High Dose Selenium Significantly Improves My Fatigue and Brain Fog

High dose selenium significantly improves my fatigue levels, and noticeably reduces my brain fog. I have consistently found selenium to be the best single supplement or drug I have tried for ME/CFS.

I found that it requires a high(ish) dose of 400 mcg of selenium each day before these benefits manifest. The best form of selenium to take is yeast-free selenomethionine, as selenomethionine the best absorbed form of selenium. Selenium must be taken on an empty stomach, to ensure it is properly assimilated.

I found that the improvements in fatigue and brain fog that selenium provides take a while to appear: it takes around 10 days of daily selenium supplementation before these improvements manifest. But these improvements begin to be noticeable by the 10 day stage. This amelioration in fatigue and brain fog is also maintained permanently, provided I continue to supplement with 400 mcg of selenium each day.

Two other people who followed the same selenium protocol as me also said that they found noticeable improvements by 10 days.

If I cease taking my daily dose of 400 mcg selenium, within about 3 or 4 days of stopping, my fatigue and brain fog will begin to get worse again. So if you want to maintain the increased energy and cognitive abilities it provides, one should take selenium on a daily basis.

I also found that if I reduce my dose to 200 mcg of selenium a day, the fatigue and fatigue and brain fog also creep back to some degree. Taking a 400 mcg daily dose of selenium seems to provide the best benefits.

The maximum daily dose of selenium is 600 mcg (ref: here), so you can even try taking higher daily doses of selenium; but I personally found that these higher doses created some irritability side effects, so I went back to 400 mcg. However, other people may be perfectly fine with these higher doses.

High Dose Selenium: Long Term Improvements in ME/CFS

This daily dose of 400 mcg of selenium also appeared create to some significant long term improvements in my ME/CFS. Two years ago, my ME/CFS was much worse than it is now: at that time, for one or two days each week, it was common for me become so tired I would sleep in bed for 18 hours of the day. Nowadays, however, I never experience these very tired days, and my overall energy levels and mental concentration levels are much improved compared to two years ago.

So I would say that before selenium, I was on the border of entering severe ME/CFS territory (in which people are mostly bedbound), but after some time on selenium, my ME/CFS improved to the point where it become moderate ME/CFS, even on border of becoming mild ME/CFS (on the ME/CFS scale of mild, moderate and severe).

Thus anyone with ME/CFS looking for a sustainable gain in energy and improvement in brain fog might want to try taking 400 mcg of selenium (as yeast-free selenomethionine) on an empty stomach for 10 days or so, and see if you experience the same benefits as I did.

Notes on Selenium Suplementation

• Other forms of selenium supplement include sodium selenate, and sodium selenite, but the absorption of these two forms in the gut is only around 50%, whereas the absorption of selenomethionine in the gut is near 100%. If you take the less absorbable forms of selenium, you may have to increase your dose to compensate for the poorer assimilation.

• Selenomethionine comes in both a yeast-free form, and a yeast-derived form. I would avoid the yeast-derived form of selenomethionine, because I found this yeast form caused significant depression symptoms when I took it, whereas the yeast-free selenomethionine had no such side effects.

• Selenium must be taken on an empty stomach to ensure good absorption.

• Selenomethionine is also referred to as L-selenomethionine (these are the same thing).

• Selenium protects against cancer, so this is another benefit of taking this supplement on a daily basis. Though it may increase the risk of prostate cancer.1

• I find the highly bioavailable methylselenocysteine form of selenium just as effective, and this is what I use now. Swanson sell an inexpensive methylselenocysteine supplement. You can buy it here. Methylselenocysteine is also called Se-methylselenocysteine and L-Se-methylselenocysteine.

I later discovered that selenomethionine, but not other forms of selenium, may induce HERV (human endogenous retrovirus) expression (see here). Not sure if this is an issue, but maybe then methylselenocysteine might be a better option than selenomethionine. Though note that HERVs may sometimes play a protective role in the immune system (see bottom of this post).

High Dose Selenium: Possible Mechanisms of Action

Selenium has a number of effects in the body that may explain why it reduces fatigue and brain fog in ME/CFS. Some of these effects are as follows:

Selenium has significant antiviral effects, as selenium deficiency is known to cause increased viral pathogenicity, and is known to make coxsackievirus B and echovirus infection more severe (coxsackievirus B and echovirus are two enteroviruses strongly linked to ME/CFS). See these studies:

• Selenium and viral virulence (full paper here)
• Increased virulence of a human enterovirus (coxsackievirus B3) in selenium-deficient mice
• Increased virulence of coxsackievirus B3 in mice due to vitamin E or selenium deficiency
• Selenium deficiency contributes to the chronic myocarditis in coxsackievirus-infected mice

• Coxsackievirus B3-resistant mice become susceptible in Se/vitamin E deficiency
• Benign human enterovirus becomes virulent in selenium-deficient mice
• Selenium deficiency and viral infection
• Selenium and host defence towards viruses
• Selenium and vitamin E status: impact on viral pathogenicity

Coxsackievirus B is capable of making viral selenoproteins, and is thereby able to reduce the body's supply of selenium. Ref: here.

Selenium promotes the antiviral Th1 immune response, and the more anti-inflammatory M2 phenotype of macrophages. Ref: here.

Selenium is a co-factor for glutathione peroxidase, which is an antioxidant enzyme that, with the help of reduced glutathione, scavenges hydrogen peroxide. This helps prevent the generation of free radicals and reactive oxygen species (ROS) by hydrogen peroxide. Furthermore, this study suggests that deficiency of glutathione peroxidase causes Coxsackie B virus to undergo genetic changes in the body making it more virulent. So glutathione peroxidase may reduce the virulence of this virus.

Genistein has been shown to elevate glutathione peroxidase and superoxide dismutase. Ref: here. So those who benefit from selenium might find further benefits from genistein, assuming the benefit comes from raised glutathione peroxidase.

The herb Gynostemma pentaphyllum also raises glutathione peroxidase. Ref: here. Vitamin E increases glutathione peroxidase. Ref: here.

Selenium deficiency increases susceptibility to glutamate-induced excitotoxicity. Ref: here.

Selenium provides partial protection against quinolinic acid neurotoxicity. Ref: here. (A full list of medications that protect against quinolinic acid given in this post).

Selenium potentiates dopaminergic function in the brain. Ref: here.

Selenium enhances the activity of T-regulatory cells (T-regs), which might have an anti-autoimmune effect. Ref: here. Other supplements which boost T-regs listed here. TGF beta-1 destroys T-regs, according to Dr Shoemaker, but losartan can reduce its levels; see this post.

Selenium increases toxic metal excretion from the body. Supplementation with just 100 mcg of selenium (in the form of selenomethionine) daily for 4 months led to a 34% reduction in levels of mercury detected in body hair. Selenium may act as a competitive inhibitor of mercury and lead absorption. However, for me the benefits of selenium appear after just 10 days, and I think that is too fast to be due to toxic metal detoxification, which takes many months.

Selenium helps counter most of the toxic effects of mercury. Mercury is only harmful because it binds to selenium and prevents it from performing its vital roles in the brain. Selenium supplementation has been shown to restore selenoprotein function and reduce the toxicity of mercury. Ref: here.

This article says:
Will Brazil nuts work.
Since quinolinic acid is a product of the kynurenine pathway...

"The kynurenine pathway (KP) plays a critical role in generating cellular energy in the form of nicotinamide adenine dinucleotide (NAD+). Because energy requirements are substantially increased during an immune response, the KP is a key regulator of the immune system."

Do you think quinolinic acid levels are increased in ME/CFS?

I will start looking at that, but does anyone have their own quick fix for this type of issue?

Looking through some old posts I haven't found anyone having luck with this.