Should You Be Taking Selenium?

| Modified on Jun 18, 2015
Selenium Supplementation

Selenium has been in the news recently as a cure or preventative for cancer. A mineral found in the soil, selenium is one of the essential elements. There have been many studies done on the relationship between selenium and the treatment cancer, diabetes, thyroid problems, cognitive function and many other ailments.

What is Selenium?

Selenium is a nonmetallic trace element rarely found in its pure state in nature. It is produced as a mining by-product of sulfite ores, such as copper, and has certain industrial uses. For us, however, a tiny dose of selenium is essential for good health.

Selenium and Glutathione

Probably the most important reason for ensuring that we have enough selenium is that our bodies need it for the production of glutathione peroxidase (GSH-Px), an antioxidant that aids every cell in our bodies to fight illness and thus maintain health.

During an illness, you need more glutathione than normal as the body uses it to remove toxins from the body. Naturally, the more glutathione we use, the less we have in supply. When glutathione levels have been depleted, free radicals accumulate and these can damage cell membranes. Depleted glutathione levels therefore need to be renewed.

Maintaining Glutathione Levels

Selenium is important for the production of glutathione in our body. Studies have shown low levels of both selenium and glutathione when people are ill.

It would seem logical to think that taking up to 200 mcg/day selenium when sick would be a good idea, but we could not find research to confirm this.

If you took selenium when you were sick, please let us know the details on how it worked for you.

Diet. When healthy, people usually get all the selenium that is needed from their food. However, people tend not to eat a balanced diet when sick, leading to the risk of a diet not rich in essential elements such as selenium.

Exercise is also a good way to help restore glutathione levels, but this is also something sick people cannot easily do.

Bioactive whey protein, made from denatured proteins and produced from raw milk (not containing hormones, pesticides or antibiotics), will help to maintain glutathione levels.

Obtaining Selenium from a Healthy Diet

Plants draw selenium from the soil, but the amount of selenium in the soil varies. In most parts of the world, there is sufficient selenium in the soil. However, in one region of China, selenium deficiency in the soil was eventually tied to people suffering from multiple ailments.

  • Selenium can be obtained from a wide variety of foods.  However, selenium from grain-based foods is dependent upon selenium levels in the soil. Most vegetables and fruits do not contain much selenium.
  • Tuna is very high in selenium (4 oz. = 123 mcg), as is other seafood such as shrimp, sardines, oysters and salmon.
  • Brazil Nuts contain 544 mcg per ounce; selenium is also found in black walnuts, cashews and macadamia nuts.
  • Whole-wheat bread has 11 mcg per slice. It is also found in other whole-wheat products, such as English muffins, pita bread, etc.
  • Meat contains selenium. On average, a 3 oz. serving of lean meat or poultry will supply 25-35 mcg of selenium.
  • Sunflower seeds supply 78 mcg of selenium per 100 grams of seeds.

Benefits of Selenium:

  • A sufficient supply of selenium is essential for the production of the critical antioxidant enzyme glutathione.  This may be the most important benefit of selenium.  It appears that benefits claimed for selenium could be the result of selenium providing for adequate levels of glutathione. 
  • Selenium helps to support the immune system.
  • It is needed to regulate thyroid function.
  • It assists in preventing cataracts.
  • Antioxidant properties of selenium may help to prevent damage to cells from free radicals. It may also work in the prevention of heart disease.
  • Selenium may help to reduce the risk of developing prostate, skin and some other cancers. See SELECT trial information below.
  • Inflammation associated with rheumatoid arthritis may be lessened by selenium.
  • Selenium is said to reduce the risk of sunburn.

The FDA and Selenium

In 2003, the FDA issued a qualified approval for selenium as a cancer preventative, with the caveat that the sale of the supplement was accompanied by a warning stating that while selenium could reduce the risks of some cancers, it might carry a carcinogenic effect for other cancers.

At the end of a rather long opinion, the bottom line is that selenium supplements can be sold, but the FDA won't allow the manufacturers to say unequivocally that the supplements will be useful in preventing cancer. In our view, the research for this stance is limited.

Selenium and Cancer

A few years ago, there was a lot of excitement about the possibility of selenium preventing cancer. Many studies tried to determine whether selenium could help to prevent cancer, either taken alone or with vitamin E. But the research results were not found to be conclusive.

The SELECT Trial for Prostate Cancer

The Selenium and Vitamin E Cancer Prevention Trial (SELECT) (SELECT) divided 35,000 men, considered to be at moderate risk of prostate cancer, into 4 groups in the U.S., Canada and Puerto Rico. This study began in 2001. Their conclusions were as follows:

Group 1: Received only synthetic Vitamin E (400 IU/360 mg/day).

Conclusion: The synthetic Vitamin E was stopped in 2008. A follow-up in 2011 revealed that more men developed prostate cancer than in the placebo group. Never take synthetic Vitamin E.

Group 2: Received only selenium (200 mcg/day as L-selenomethionine).

Conclusion: This did not work as expected. The researchers speculated that the problem was the form of selenium given to the men. They received selenomethionine, which had a synthetic component. The researchers felt that selenium yeast, used in previous trials at a dosage of 200 mcg/day, would have been a better choice, but only for men who began the trial at a low selenium level.

Group 3: Received both Vitamin E and selenium.

Conclusion: Again, the researchers felt that the form and dosage had been wrong. Selenium yeast had previously been shown to have a protective effect in past trials.  They felt that the type and dosage were wrong for the vitamin E. Natural vitamin E at a dosage of 50 IU (compared to the 400 IU used in SELECT) was proven beneficial in other trials.

Group 4: Received only a placebo


IMPORTANT: Before starting to take selenium, it's important to know your selenium level. Selenium had a protective effect for men who had a low selenium level. However, men who started taking selenium when they already had a high level of selenium developed an increased risk of developing aggressive prostate cancer.

A blood test for selenium without insurance at a walk-in lab costs about $150.00.

The SELECT trials were studying prostate cancer. Whether taking natural Vitamin E and selenium yeast at the recommended doses would be helpful against other cancers is unknown.

Selenium and Alzheimer’s

Research has been inconclusive as to whether selenium supplements could prevent Alzheimer’s. A French study of over 4,000 people aged 45-60 found that those who took a supplement containing 100 mcg selenium, ascorbic acid, vitamin E, beta-carotene and zinc for 8 years had improved memory and speech compared to those taking a placebo. However, the study could not say whether or not selenium by itself would have had the same effect.of over 4,000 people aged 45-60 found that those who took a supplement for 8 years containing 100 mcg selenium, ascorbic acid, vitamin E, beta-carotene and zinc had improved memory and speech compared to those taking a placebo. However, they could not say whether or not selenium by itself would have the same effect.

Selenium and Diabetes

Some studies show a possible link between as little as 200 mcg selenium and an increased risk of Type 2 Diabetes.

Recommended Selenium Doses

  • Children:                       20 – 40 mcg (micrograms)/day
  • Adults:                          55 mcg/day
  • Pregnant women:          60 mcg/day
  • Breastfeeding women:   70 mcg/day

How Much Selenium is Too Much?

According to the U.S. Institute of Medicine, over 400 mcg of selenium a day is considered an overdose. Over 800 mcg would be a toxic level, leading to selenosis. This can result in hair loss, gastrointestinal upset, garlicky breath, discolored nails, irritability, fatigue and possibly mild nerve damage.

It needs to be pointed out that selenium can be ingested during the day from multiple sources, including food, selenium supplements and multivitamins or other supplements containing selenium. Taking 2 - 200 mcg capsules would result in a daily dose of over 400 mcg for most people.

Selenium is essential, especially to maintain necessary glutathione levels, but adequate amounts can normally be received from food. If taking a supplement, be careful as to the form of selenium taken and the dosage.

Please let us know if you take selenium, the dosage you take, and how it is working for you!

General Feedback

Posted by Anthony (Philadelphia, Pa) on 05/31/2012

Well I had a 24 hr urine test done for heavy metals and in this included selenium. Well everything came back normal except my selenium The normal range is 150-250 and I was 355. My doctor was shocked and could not find I reason as to why.

I do take selenium supplements but I just started them several days before, besides that there is not much else of selenium in my diet.

I read there could be a connection between high selenium and diabetes but I have a well controlled diet and my fasting glucose was 86 and A1C was well within the normal range.

The other thing I read was that Selenium and thyroid work together... Something along those lines. I just couldn't understand if I would be hypothyroid or hyper in relation to selenium being high.

Any info would be helpful, thanks!

Replied by Timh
(Louisville, Ky, Usa)
2063 posts

Anthony, to help your body utilize Selenium take 400-800 iu Vitamin E (mixed natural tocopherols) daily. The Selenium will bond readily w/ the E and get incorporated into your tissues (instead of floating around in the blood) as an antioxidant complex boosting glutathione levels.

Replied by Anthony
(Philadelphia, Pa)

Thanks for the response. My doc and I spoke and I'm gonna hold off on the selenium for a month and we are gonna do the 24 hr. urine again. Once I get that back I'll see where my levels are and go from there. Thanks!

Replied by Anthony
(Philadelphia, Pa)

Hi, Well, I recently had a urine test and blood work done. I posted a day ago that my urine test came back with very high selenium amount; over 100mcg normal value. Well, my blood work just came in and a few things are off. Maybe someone can guide me a little as I am concerned but my doc didn't seem so. The T4 and T3 were normal but I put the values incase they mean something inregards to the TSH reflex. Thanks!

TSH w/ Reflex to FT4 was 0.39 (0.40-4.50 is normal)
T4, Free was 1. 4 (0.8-1.8 is normal)
T3 uptake was 35 (22-35% is normal)
Alkaline Phosphate was 38 (Low) (40-115 is normal)
Albumin/Globulin ratio was 2. 2 (high) (1.0 - 2.1 is normal)

Thanks again!

Replied by Bill
(San Fernando, Philippines)

Hi Anthony... Selenium is highly important and very necessary when you take higher dose iodine because selenium is used in two ways in the thyroid.

First, selenium is essential for the manufacture of T3 and T4 to prevent the anti-body auto-immune response. Thyroglobulin stored in the thyroid is converted to T3 and T4 by an enzyme called thyroid peroxidase. And hydrogen peroxide -- a free radical metabolite that is normally always produced -- is given off during this reaction. Normally glutathione peroxidase -- an anti-oxidant -- neutralizes and prevents build up of hydrogen peroxide free radicals in the thyroid cells. However, selenium is the central metallic atom for glutathione peroxidase(GP) so if selenium is depleted in diet you may not have enough GP to prevent thyroid cell free radical damage and the inevitable anti-body autoimmune response(thyroid nodule formation and inflammation). So you must always take selenium with higher dose lugol's iodine for this reason.

Secondly, selenium is also involved in the conversion of T4 to the more active T3 form. So if selenium is depleted in the body, there will therefore be higher T4 and lower T3 readings. T4 is also used in the feedback loop with the pituitary gland -- so a false high T4 reading will immediately act to suppress and reduce both T3 and T4 production in the thyroid -- giving an overall hypothyroid effect.

This is why -- if you are taking higher dose lugol's iodine -- you should always follow The Iodine Protocol. Every single one of the nutrients in this protocol is there for a reason. For instance, magnesium is in the protocol to regulate excess calcium in the body(excess calcium inhibits iodine uptake) and magnesium is also involved as a coenzyme with l-tyrosine that converts iodide to iodine for initial storage in the thyroid. So, if you are defficient magnesium in your diet -- you also run the risk of being hypothyroid. The western diet is also well known to be defficient in both magnesium as well as iodine.

A normal maintenance dose of selenium is between 100 mcg and 200 mcg per day depending on your diet.

Replied by Bill
(San Fernando, Philippines)

Hi Anthony... Although your FT3, FT4, TSH etc seem fairly normal, there is one other possible factor that may be causing you problems -- which is Reverse T3 and Reverse T4 clearance.

RT3 and RT4 are produced at a constant output level to further balance the ratio and uptake of mainly FT3/FT4 in the body. This balancing/adjustment of FT3 and FT4 with RT3 and RT4 is a normal body mechanism which mainly happens in the liver. RT3 and RT4 work at the cellular level -- binding to T3 and T4 tissue sites to deiberately inhibit and balance FT3 and FT4 uptake. So if the clearance or regulation of RT3 and RT4 is either inadequate or excessive then this can also cause apparent thyroid problems and symptoms.

RT3 and RT4 clearance problems are normally concerned and associated with liver/kidney problems and not the thyroid.

So, if you still believe that you have hyper- or hypo-thyroid symptoms, perhaps best if you get an RT3 and RT4 check to further confirm if there are any problems in this area.

Replied by Anthony
(Philadelphia, Pa)

Hi Bill, Thanks for all the info. Im not taking iodine. I'm not sure if you thought I was. And also, what do these numbers represent, that I'm hypothyroid or hyper? Wouldnt it represent hyper?? I do know a little bit about the thyroid, but not enough to know what I should do.

I do have Ulcerative colitis, a white tongue, and I do believe candida. Would iodine be wise to take? Also, should I be concerned about the Alkaline phosphate and albumin? Thanks again!

Replied by Bill
(San Fernando, Philippines)

Hi Anthony... Your FT4 is in the normal range so your TSH output may be low or incorrect for normalizing FT3 and FT4. The strange thing is that your FT4 is Ok but your FT3 is actually borderline high. A low level of TSH should produce lower levels of FT3 & FT4 but this is not the case. This is confusing, but can be explained in the following way:

* If your Reverse T3 and Reverse FT4 levels are too high -- this will not be reflected in any of the readings you have so far obtained from your blood and urine levels. This can only be obtained from separate and specific RT3 and RT4 readings from the blood. If RT3 and RT4 are high then the absorbtion of FT3 & FT4 at the cellular level will be low -- both RT3 and RT4 inhibit FT3 and FT4 abroption throughout the body -- giving symptoms such as low energy, lethargy, brain fog etc. Therefore as I've said before -- You must get your RT3 & RT4 levels checked to be sure.

* High RT3 & RT4 levels, high albumin levels and alkaline phosphate levels all tend to indicate problems with the liver or kidneys -- not the thyroid. So get your liver(AST, ALT levels etc) and kidney checked out.

* A low TSH output with normal FT3 & FT4 could also indicate problems with the pituitary gland. Both the pineal and pituitary gland are absorption targets for heavy metals and for fluorine and bromine which can definitely effect hormone output levels. So you might need to detox your pituitary gland using green tea, chlorella and cilantro as advised on this site.

* You also have candida and colitis and this is also reason enough to cause debillitating effects on your thyroid and would also indicate that your body needs detoxing. Candida always affects and suppresses thyroid performance over time.

* Candida always drags down the thyroid. And if you don't get rid of the candida, your thyroid and colitis problems may well worsen over time.

Supplementing organic aloe vera juice and regular supplementation of food grade Bentonite clay should help the colitis, but -- from my own experience -- you will have a tough time curing colitis and your thyroid problems if you do not get rid of the candida first. See the Anti-Candida Protocol shown in the link.

Replied by Ant
(Philadelphia, Pa)

Hi Bill, Thanks for getting back to me. The 3 symptoms you have described (fatigue, lethargy, memory issue - my biggest issue) I have them all. My colitis is not that bad. It's more proctitis. I only use the bathroom 1-2 times a day. My bowel movements are never the same, meaning very thin, broken up sometimes; other times normal, sometimes it burns other times it doesn't. I began taking HCL tablets again to help with digestion. I burp alot, however my diet is pretty good. I def believe I have some sort of candida however it my digestion got better I believe the Candida would. I will go see an endocronologist soon. Should I take iodine or no? I wouldn't want it to make me more hyper you know.

Also, I take Lialda so maybe that is affected my liver/kidney, besides that I take vit d, zinc, cysteine, lysine, thats it! Well, at least the levels were low. Im getting them checked in 3 weeks again.

Also, do you know a reliable place to get hair analysis done? Thanks!

Replied by Bill
(San Fernando, Philippines)

Hi Ant... Here is what I found on (an FDA approved site) regarding the side-effects of Lialda:

The most serious adverse reactions seen in Lialda clinical trials or with other products that contain or are metabolized to mesalamine are:

* Renal impairment, including renal failure

* Mesalamine-induced acute intolerance syndrome

* Hypersensitivity reactions

* Hepatic impairment, including hepatic failure "

"In two 8-week placebo-controlled clinical trials involving 535 ulcerative colitis patients, 356 received 2. 4 g/day or 4. 8 g/day Lialda tablets and 179 received placebo. The most frequent adverse reaction leading to discontinuation from Lialda therapy was exacerbation of ulcerative colitis (0.8%). Pancreatitis occurred in less than 1% of patients during clinical trials and resulted in discontinuation of therapy with Lialda in patients experiencing this event. " Source:

Regarding taking iodine for your problems -- I am wary of advising this now because I have no idea what the contraindications would be when taken with Lialda. So best to ask the endocrinologist about this.

You can get a hair analysis done at any naturopath clinic in your area -- its not expensive.

Prevents Nightmares

1 User Review
5 star (1) 

Posted by Violette (Usa) on 03/24/2015

After suffering from terrifying dreams for many years, I found out by accident selenium cured them. As soon as my dreams become oppressive if I run out I take it again and it almost 100% cures the nightmares. I am also very intolerant of gluten. Never ever saw this information anywhere, hope it helps.

Replied by Prioris
(Fl., US)

I think terrifying nightmares are usually a sign of being haunted. There may be entities that could be harassing you while you sleep. Maybe you were physiologically weakened and that allowed an opening in your psychic shield to these entities. By taking the selenium, it may have made your aura more stronger hence closing off some psychic vulnerability you had. Glad you had some success with selenium.

Selenium and Type II Diabetes Risk

Posted by Rsw (Uniontown, Oh) on 08/20/2014

I take iodine five days a week for hypothyroidism, along with selenium and other companion supplements. However, I recently stumbled onto a U of Maryland study that seemed to show that as little as 200 mcg of selenium/day can significantly increase one's chances of type II diabetes. There is a Pub Med article on this, also.

Has anyone else heard of this? What do you think? Thank you.

Replied by Timh
2063 posts

@Rsw: In my estimation, institutions which are funded by big pharma are going to exhibit a marked bias for "medication" and against "nutrition". This is obvious everywhere in medical practice as physicians want to no all supplements one is taking so to reduce interaction w/ "medication". From a ND perspective, one should always seek to maintain proper essential vit/min and adjust any medication from there.

A very reliable first stop for nutrition information, again, imho, is the Linus Pauling Institute. This article

addresses this finding, but notice the educational approach on the entire subject of Selenium as it relates to the human body.

I think it was the famous musician John Denver who saw several specialist for an infertility issue w/ no help, when eventually he found that his problem was simply a Selenium deficiency. This is that bias problem again.

Replied by Mmsg
(Somewhere, Europe)

Rsw, why don't you just eat a Brazil nut or two daily? You won't get too much selenium in that.

Replied by Nanowriter
(Hotspot, Texas)

I read that study and was kind of nonplussed as well. But then I remembered how iodine supplementation can lead to problems if the patient is low on selenium as well as iodine. We run the risk of exacerbating another nutrient's deficiency when supplementing another.

Perhaps the selenium supplementation caused an already low level of chromium and/or vanadium to go so low as to cause diabetes, as these two minerals are used by people to treat their diabetes.

Replied by Rss
(Uniontown, OH)

Thank you Timh, Mmsg and Nanowriter for taking the time to give me your input on selenium supplementation. You have given me several different paths to think about adopting. It's because of generous people like you that Earth Clinic is my absolute favorite site and I am thankful for finding such innovative and out of the box thinking on medical and other issues. The biggest hearts can be found right here. Thanks!

Selenium Side Effects

1 User Review

Posted by R. (Dallas, Texas, Usa) on 03/21/2010

Just a warning to do your research on Selenium, to avoid bad side effects from too much Selenium! I was taking too much and had some pretty bad side effects. Although everyone is different and can tolerate different amounts of drugs/vitamins/supplements you should still be cautious with everything you take. I just learned the hard way!

I was taking:

200mcg.(mcg.= micrograms) through a supplement.

100mcg. was in my multi-vitamin/ which I knew there was some, but, that is 143% of our daily recommended intake.

1 brazil nut equals your whole recommended dietary intake. I was eating a handful a day!

You also get your daily amount in food: Fish, tuna, eggs, bread, brown rice, oats, turkey, and other nuts.. I did not know any of these extra ways of getting Selenium.

My daily intake was probably 700 - 900 mcg a day, or more! 200mcg. is the recommended daily amount. It also says some people can take up to 400mcg daily, and over 800mcg. could be toxic, and you could get Selenosis!

Also Vitamin E taken at the same time as Selenium, enhances the Selenium! Which I was taking the two at the same time!

After 4 days of not taking Selenium supplements, I am about 80% better.

Here is a website for further info on Selenium:

Thyroid Issues

1 User Review
5 star (1) 

Posted by Wendy (Plover, WI U.S.A) on 10/29/2007

Hi, Se helps the thyroid which slows down due to celiac. Faster working thyroid helps increase oxygen to the brain cells. Brain cells need more oxygen than other cells. Heavy metals block the thyroid medicine from being used and may block how the hemoglobin works. I was full of heavy metals. Colloidal siver poisoned me. It was the worst hell. I don't recommend anyone take colloidal silver. They may build it up like I did.

Replied by Bessie
(Vancouver, Canada)

Regarding Earth Clinic's query about "Se" in someone's post. It stands for Selenium which is extremely helpful for those who have problems with their thyroid. By the way, I love this site and check it regularly. I've learned so much. Thank you!

Replied by Khakimo
(Atlanta, Usa)

To Wendy - I would question your source of colloidal silver? Were you tested and told you had toxic levels of SILVER in your body? You must have a bad source as colloidal metals DO NOT build up in your system and it is an invaluable healing agent. I took a tablespoon daily for 10 years and then the last couple of years have not taken it only due to finances. BUT - I have not had so much as a cold for 12 years since I first started taking it - and I used to get one or two bad colds every year.

I gave it to someone who had a flu and had been taking antibiotics for several days with NO change - in a matter of about 4 hours their flu was GONE. I have also over the years treated my pets with it (putting it in their water). I have given it to my cats when they were sick and I didn't know why - and fixed them up immediately. Another thing it is very good for - you never have to worry about eating some bad food - on the few occasions I did, colloidal silver cleared up the problems immediately.

It is a huge disservice to tell people not to use it - it is very reasonably priced and if properly made CANNOT build up silver in your body.