Important Update on Selenium Supplementation | Chris Kresser

Important Update on Selenium Supplementation

by Chris Kresser

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A while back I wrote an article on the role of selenium in autoimmune thyroid disease.

I summarized several studies which found that selenium supplementation reduced inflammation and damage to thyroid tissue, lowered thyroid antibody levels in the blood, and improved the conversion of T4 to T3.

However, I also sounded a note of caution when it comes to selenium supplementation:

“These preliminary studies show the positive effects of selenium supplementation on inflammatory activity in autoimmune thyroid conditions, but the long term effects of supplementation on thyroid health are still unknown. And we know that selenium is an essential component of the enzymes that convert T4 to T3, but whether supplementation will increase serum T3 levels is unclear.

While it seems that selenium supplementation would be an obvious solution to poor thyroid function, long term consumption of high doses of selenium can lead to complications such as gastrointestinal upsets, hair loss, white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage. (1) Additionally, supplementing selenium in the context of low iodine status may actually aggravate hypothyroidism. Mario Renato Iwakura discusses this particular topic extensively on Paul Jaminet’s Perfect Health Diet blog.

For now, the best option for most people may be to include selenium-rich foods in the context of a healthy Paleo diet.”

A study published last year—which I just came across a few weeks ago—appears to validate this caution, at least for middle-aged men. (2) It was a large clinical trial (with over 35,000 participants) that examined the relationship between baseline selenium status, supplementation with selenium and vitamin E (either together or separately), and future rates of prostate cancer in men over 55 years of age.

Here’s what the researchers found:

  • Baseline selenium status alone was not associated with prostate cancer risk.
  • In men with high baseline toenail selenium (>60th percentile), selenium supplementation of 200 mcg/d increased the risk of high-grade prostate cancer by 62% when taken alone, and by 224% when taken with vitamin E.
  • In men with normal or low baseline toenail selenium (<60th percentile), selenium supplementation of 200 mcg/d (either alone or with vitamin E) did not substantially increase or decrease the risk of prostate cancer.

It’s worth pointing out that these findings contradict two previous (and considerably smaller) observational studies in the US which found that low toenail selenium status increases the risk of prostate cancer. (3, 4) In addition, a large Dutch study including over 58,000 participants, found that those with the highest toenail selenium status had a 37% lower risk of prostate cancer than those with the lowest selenium status. (5)

Should you be supplementing with selenium? Find out what @ChrisKresser has to say!

However, in the US selenium levels are typically much higher than they are in Holland, where deficiency is widespread. While it’s entirely possible that the very low selenium levels seen in Holland are associated with increased prostate cancer risk, there does not appear to be a correlation between selenium and prostate cancer in the US—at least within the ranges of toenail selenium found in US men over 55 years of age.

So what are we to make of this? A growing body of research suggests that the effects of micronutrient supplementation are dependent upon the status of that nutrient in the target population. (6) If baseline levels of a particular nutrient are low, supplementation may lead to improved outcomes. But if baseline levels are normal or high, supplementation may cause harm—as it appears to have done in this study. This shouldn’t be too much of a surprise. Most nutrients have a “U-shaped curve”, which means that both too little and too much can cause problems.

On the other hand, several studies indicate that supplementing with selenium has several benefits for people with autoimmune thyroid disease, including reduced inflammation and damage to thyroid tissue. At least one study found that selenium supplementation produced these benefits even when selenium levels were normal at baseline. (7) Since both Hashimoto’s and Graves’ disease are associated with increased morbidity and mortality, an intervention that reduces the autoimmune/inflammatory burden in these conditions might be expected reduce morbidity and mortality.

There’s little doubt that maintaining adequate selenium levels is important to immune and thyroid function. But given the potential long-term risk of supplementation, I think the best option for most people is to meet their need for selenium by eating selenium-rich foods. Great sources include: brazil nuts, crimini mushrooms, cod, shrimp, tuna, halibut, salmon, scallops, chicken, eggs, shiitake mushrooms, lamb, and turkey. Brazil nuts are a particularly rich source; just 2–3 a day will provide roughly 200 mcg of selenium, which is the amount used in many of the autoimmune thyroid studies.

Finally, while this study was focused on prostate cancer risk in men over 55, it’s probably prudent to assume that long-term selenium supplementation in both younger men and women of any age may also have undesirable effects.

I will, of course, continue to keep an eye on the research in this area and report back if any new findings come to light that would change my recommendation.


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  1. I have very low T3 though my T4 is nearly okay. I have been cold nearly all of my life. This is very interesting. I refuse to take synthetic lirothyronine for it and I try to manage it with food.

  2. As a patient with Hashimoto I would like to begin supplementing with Iiodine and selenium together, how long should I continue to supplement selenium before it could become harmful and if I stop supplementing with selenium should I also stop taking iodine?

  3. so many fake users here probably from big pharma with their own agenda.. spreading confusion and encouraging to use synthetic selenium by giving dumb reasons or personal experiences. there are 2 posts for example that were posted in the same day, same month, same year and within the same hour, that bashes the brazil nuts. the way of writing is same with plenty other clues and patterns of writting. do not BELIEVE that all comments are from normal people. i know someone who used to work for such a job, until he left it because he felt very wrong about it.

    big pharma, companies , have hundreds of thousands of websites and comments posted with fake information. don’t believe everything, think for yourself!

  4. Is there something wrong with taking Armor Thyroid? I have read a lot here about a bunch of different strategies (even naltrexone), but no one is talking about the natural hormones that are apparently almost identical to our own.

  5. Flawed Selenium Study
    The overwhelming scientific evidence supports selenium’s anticancer activity, and favors prudent dietary supplementation with selenium. Confusion arose, however, in 2009 with the publication of a single negative study, one that has contributed to substantial misinformation about the value of selenium in cancer prevention. Notably, those with false negative results may teach us more about selenium’s role in preventing malignancies than more positive reports.

    Known as SELECT (for Selenium and Vitamin E Cancer Prevention Trial), the study appeared to show that selenium, alone or in combination with vitamin E, had no detectable effect on preventing cancers.

    Many experts have since questioned the SELECT trial’s methodology and conclusions.One problem with that study was that it used only a SINGLE form of selenium. This selenium compound is just one of several different forms in which selenium is available for nutritional supplementation. The major flaw in this study is that it used synthetic alpha tocopherol, which displaced critical gamma tocopherol from cells, thereby increasing cancer risk.

  6. Danish researchers from Copenhagen University have discovered that methylated selenium compounds found in garlic, broccoli and selenium yeast can better enable the immune system to fight cancer.
    I take a 100mcg tablet of organic high-selenium yeast every 1-2 days, especially because I am worried about the mercury from seafood.

  7. I ask myself is soaking of brazil nuts will just also wash out the selenocysteine out of the nuts. because this is water soluble. In that case the brazil nuts are worthless as selenium delivering food.

    I guess there is no evidence about that?! We only think about soaking helps with phytates but why should it only lead to decreases of phytates? All water soluble minerals and vitamins could be lost by soaking?!

    I bet there was no research done so how do we know?

    • How about drinking the water you soak the nuts in? Also, I’m not too sure that eating 2 to 3 Brazil Nuts a day will have enough phytates to be problematic.

      Just a thought.

  8. Dear Chris, you mentioned the 35000 men trial. Their selenium [Se] starting levels were all above 1.6 at the begining. Prof Gerhard Schrauzer ex UCSD. a lifetime Se expert told me enzymes are activated only when Se concentration is about 1.7 mcml/lt Then the numerous benefits occur! My Se plasma blood test was 1.0 mcml/lt. Then I began taking 200 mcg/d sod.selenate. At about 1.6, thats when my prostate problem fixed,still is, libido increased, finger nails grew twice as fast. Thats why the NZ recommended level is set at 1.6-1.9. That SELECT trial, confirmed Gerhard’s figures beautifully.

  9. Articles like this one drive me crazy. Should not one test selenium status before supplementing selenium?

    I have Hashimoto’s that’s subclinical hypothyroidism on the brink of needing thyroid hormone.

    Thinking that I would supplement with iodine, I followed the instructions that said supplementation with selenium was a prerequisite. I tried eating one Brazil nut a day for a few weeks and my selenium went significantly out of range!

    It took several months with no Brazil nuts to go back to where it is now: My blood selenium level is 245.00 ug/L, range 100-340.

    It seems I get plenty of selenium from the fresh, local veggies I eat (N. California farmland has lots of selenium). Can I just add iodine? I cannot find any advice anywhere about iodine supplementation when selenium is adequate.

    • if you want good iodine information, check out dr. flechas online or dr. brownstein online, both are great resources. the iodine thing is so controversial! good luck. i take it and i definitely feel better (i also have hashimoto’s.) the iodine is tricky but many docs will freak out and tell you not to take it, but flechas and brownstein agree that it’s beneficial and not dangerous.

        • To Kelly who said “That website is hardly objective. And most of their research is not peer-reviewed.” It is unclear what website you are referring to. If you are referring to one about iodine then you are dead wrong. There is abundant peer reviews on iodine’s use in medicine. Dr Guy Abraham (emeritus professor UCLA obstetrics, gynecology and endocrinology) lists his references indicating those directly involved in his “Iodine Project” research carried out in the 1990’s at and there are many other doctors now working independently with iodine clinically. These doctors share and compare their clinical observations. So all their work is EXTREMELY objective – more so than their opponents. There are so many of them now you can hardly claim any truth in saying Guy Abraham is not peer reviewed.

    • I have read that Cleveland Hospital studies recommend no higher than 2 mcg/day.. But most other studies recommend no more than 4 mcg/day because of negative side effects.
      It seems like the more i research hypothyroidism,iodine and selenium,the more confused it get…

  10. Heard in another group on FB that Chris now recommends 200 mcgs selenium only 2 or 3 times per week rather than daily. Can anyone confirm? Is that to avoid having too high levels of selenium? Thanks.

  11. Chris, I have just been ‘diagnosed’ long-distance with Hashimoto’s, by a naturopathic doctor. I trust her but I’m wondering if I should have an endocrinologist confirm the diagnosis just to have an in-person second opinion. I’m feeling a bit overwhelmed – I suspected thyroid and slow metabolism because I’ve struggled to lose weight – but I didn’t expect I would have an autoimmune disease. I just want to make sure I’m being wise going forward. Thoughts? Thanks so much!

    • I’ve had the same issue saw several doctors and a naturalist on top of that I recently started going to an endrogronologist I recommend you do the same she changed me from armor to synthroid but she will be testing me every 3 months
      Good luck

      • If you suspect hypothyroidism or Hashimoto’s disease, check out Stop the Thyroid Madness website. You want to test: TSH (as it can point to more than hypothyroidism); Free T4 (this is a storage hormone that needs to convert to T3); Free T3 (this is the thyroid hormone that the cells of our body use); Reverse T3 (this is a byproduct of the T4 to T3 conversion–it will keep you hypo if it is too high); TPO and TgAb (for Hashi); TSI and TrAb (for Graves, it is possible to have both conditions). And, most importantly, get a copy of your results and it is not about being “in range”. It is about “where” in range your numbers fall.

  12. You have to supplement Iodine at the same time, otherwise you are likely creating hypothyroidism. You don’t see too many 100% a study they did in Africa(zaire I believe), when they supplemented children with cretinism with selenium they all became more hypothyroid(and the majority of normal children went hypo, while others increased). Low iodine + selenium = hyo. They also found the same effect looking at rat thyroid tissue and dosing too high of one or the other causes goiter.

    • No this doesn’t apply for those with hashimotos disease (and other causes of thyroids disorder) outside of your example (Africa, malnutrition). I have hashimotos disease, unintentionaly took iodine via another supplement that included it in ingredients, and I started to sleep less and less during the week I took it. After I was really sleep deprived from iodine intake (now causing hyperthyroid symptoms), I stopped and crashed for about a week to recover. Had to drop that semester at college thanks to iodine.

      • Because I can’t edit the above post, I meant to say “crashed for a month”. And the supplement was Attend (for ADD symptoms). apparently hypothyroid fully causes ADD symptoms, so I stopped taking stuff that would focus on those symptoms, and instead focus on lowering my thyroid antibodies.

          • Sorry I didn’t mean I was yet successful in lowering my antibodies. I’ve been taking selenium 200mcg for 1-2 months now daily, and haven’t yet checked the count. I’ve got nothing new, unfortunately, to reduce antibodies.

          • I have lowered my antibodies by 33% in five months – I follow an Auto Immune Paleolithic diet – with zero cheating or it doesn’t work. I do accupuncture, supplements, classical stretching daily, healed my leaky gut etc., and in short, I’m a new person. Top endocrinologists couldn’t fix me – I was disabled – now I feel better in some ways than I have in 30 years and continue to improve every day. We tend to think of lifestyle as minor – medicine as major when in fact it’s only lifestyle changes that cure the root cause of anything. I suggest reading Hashimotos Thyroditis The Root Cause by Izabelka Wentz.

            • I just purchased Dr. Wentz’s book along with Karen Frazier’s cookbook for Hashimotos and after less than a week I’m feeling better. As a Clinical Chemist, I find it difficult to accept selenium supplementation due to toxicity concerns but I will eat 2-3 Brazil nuts daily.

              • The issue with relying on food sources for nurtients is that it’s an inconsistent source. With farming practices it’s difficult if not impossible to accurately assess the vitamin/nutrient levels in foods.

                • I agree. Doesnt do too well if nutrients arent be absorbed properly. And who can afford tests to determine values of any nutrients in foods eaten? I am cautious with supps,vities. I do iodine (goiter) ans supp with selenium. Some is in ionic liquid form, some in unradiated raw organic brazil nuts.
                  I just dont overdo. 🙂

              • So can anyone say what we’re suppose to take in The form of Seleium Yeast? These answers are absolutely crazy. All of you are making no sense on what is right or wrong! Your stepping all over yourself switch a different answer. Where is a real site that the people know what their talking about . Seleium has been around a long time with a lot of reseaech involved. No one has said anything about the research related to depression. Anyone have any solid evidence here? What about Seleium and Krill oil or Seleium Astaxanthin ? This is the most powerful antioxidant to date. Y’all are only confusing everyone that reads your post. Get some real answerers to share or please don’t share!!!

  13. Tengo 62 años de edad y me suplementó con 200 mg de Selenio de GNC y vitamina E, casi a diario desde hace aproximadamente 3 años y tengo una salud excelente. Adicionalmente tomo vitamina B12, acido folico, 300 mg de vitamina B6, 3 gramos de vitamina C, Cloruro de Magnesio y 50 mg de zinc.

  14. I wouldn’t count on food to ensure adequate selenium. The amount of Se in Brazil nuts can vary tenfold!
    You won’t get some severe Se deficiency disease like cardiomyopathy, but will you get enough to reduce cancer risk? Questionable…..

    Read my blog…….for more details on Se and a cursory rebuttal of the flawed SELECT study.

    In optimal health,
    Bob Iafelice, MS, RD, LD

  15. The best Selenium source I’ve found is kidney (beef or lamb). Really high levels of Selenium, so once a week is fine. No need for supplementation, plus, I also find that it’s self-limiting, because if I eat a lot it becomes slightly repulsive.

  16. Today I got my blood results for Selenium. It was 236 (Range 60-160) No wonder my hair is falling out. What can I do to lower this besides stop supplementing with the 200mg I was taking a day?

    Thanks Chris!

  17. What form of selenium was in those studies? Isn’t there a form that’s toxic (sodium selenite/selenate) and chelated forms that are not?

    Could that be a factor in the findings?

    • @rawdawg

      Yes, i make the same point above. We know that not all supplements are equal. Some are natural, non toxic, and effective, while others are unnatural, toxic, and harmful.

      Chris, why did you not emphasize this from the studies referenced? It makes all the difference. It could mean the studies are not very meaningful if an unnatural form was used – which I suspect is the case. The studies would then only imply dont use an unnatural form of selenium and vitamin E, which we already know is bad. These studies are likely useless for this whole discussion.

  18. I take 100 mg of selenium when I eat fish as our functional med MD said it helps bind mercury in the gut. I also have Hashimoto’s and get about 50 mg in a multi he has me taking. Does selenium help us get rid of mercury? Is taking 100 mg only when you eat fish maybe 1-2x week safe?

    • Laurie, you probably mean 50 and 100 *mcg* selenium, since 50 or 100 mg would be a massive overdose. Most people could tolerate the amounts you mention, but some such as myself would not.

  19. This was great, thanks for sharing! This seems to be the case for many micronutrients, especially those involved in oxidation/antioxidant (vitamin E, beta-carotene). It usually boils down to whole foods being the better option. I wonder where this breaks down though. What do you think the effects would be of eating a dose of brazil nuts daily in a population with a high baseline selenium status? I suppose their high selenium status would be due to a diet already high in selenium (or is there a biological component?). Does the selenium in a whole food matrix protect against the negative effects of the high selenium dose?

  20. How do you get your selenium levels tested? My local lab doesn’t do toenail testing. Is it through hair analysis, blood, urine?? Many thanks!

  21. I would like to know in the studies referenced about selenium and vitamin e supplementation increasing the risk of prostate cancer, what types of selenium and vitamin e were used (the summary referenced does not say)? It makes a HUGE difference. I strongly suspect the types that were supplemented with were synthetic unnatural toxic forms, not whole food based natural forms. Selenium in the form of selenomethionine is not a good form to supplement with and vitamin E as dl-alpha tocopherol is a toxic poison made from coal tar – it is NOT natural. It belongs in the trash. It is often the case in these studies that the researchers have no clue what they are talking about and publish studies making generalizations that are completely wrong. I suspect that is the case with these studies because in general conventional doctors are clueless when it comes to nutrition.

    I am very surprised and disappointed that Chris did not bring up this fact. For example there was a study that came out pretty recently that claimed vitamin E supplementation increased risk of prostate cancer (see The type of vitamin E used in the study was dl-alpha tocopherol – a toxic unnatural form that no one should supplement with. It is derived from coal tar, not food. Unlike d-alpha-tocopherol.

    The book “The Life Bridge” discusses for example the difference between selenomethionine and organic yeast bound selenium. There is a HUGE difference. HUGE. Selenomethionine has almost no antioxidant activity whereas yeast bound has profound antioxidant activity. Also there are 8 forms of vitamin E, 4 tocopherols and 4 tocotrienols, not just one form. Ignorant researchers do not bring this up sometimes (maybe because they just dont know) and make grossly wrong generalizations. I seriously doubt tocotrienols were used in any of these studies, although they are the most biologically active forms of vitamin E.

    The point is that the form supplemented with MUST be taken into account. Of course too much selenium or vitamin e in any form is not healthy. But if you are going to supplement, use a natural whole food organically bound form. It not only will actually work for you but it will not be toxic and cause harm.

    Selenium, in the whole food form, is considered by many cancer experts the number one protocol to prevent cancer in general. This is important to keep in mind and low selenium can cause all kinds of physiological problems. It is most concentrated in the liver, kidneys, and thyroid and is vitally important for the proper function of all three. A deficiency will cause liver malfunction, kidney malfunction, and thyroid malfunction. Selenium is the most important nutrient for the activation and function of glutathione peroxidase, a very important antioxidant. It also directly affects gene expression and thus even a slight deficiency in selenium can have devastating effects in the long term. Selenium is also very effective for protecting against mercury poisoning because selenium binds to mercury. In other words selenium sufficiency is incredibly important to health.

    • Yes, you are right about the vitamin E! Alpha tocopherol is probably the cheapest & is therefore used in most studies & hence the lack of benefits.

  22. Excellent post, as usual! As a Functional Medicine specialist we usually measure Se levels if we are planning long term supplementation. I practice in India, where few studies from Northern India have shown excess Se in the soil. While it is ok to supplement with small quantities of Se, higher doese & long term term use would mandate measuring in the patient. ( Similar to iodine supplementation).

    • Why not just keep an eye out for actual Se toxicity symptoms (such as the nails) as they are all reversible in time anyway. I question how much test results prove. What’s the documentation of their evidential value? And even if you get a test result on day x, a week later the result could be different anyway. One thing that’s guaranteed is you have to spend money and time on them.

  23. Chris,

    What are your thoughts about the genotoxic and carcinogenic aflatoxins present in brazil nuts? I decided against eating brazil nuts regularly for the selenium after learning that brazil nuts are susceptible to aflatoxin contamination, produced by Aspergillus nomius and Aspergillus flavus fungi present on the nut. Eating brazil nuts regularly could result in chronic toxicity of aflatoxin, which can cause cancer.

  24. I believe Chris has written about Low Dose Naltrexone for Hashi’s in the past. There’s a large group of over 4,000 members in the Beating Thyroid Disease with Low Dose Nalxtrexone group ( For anyone with Hashi’s, LDN can be highly beneficial. You must learn how to dose properly and the folks there can provide some very useful advice.

    Also, you might want to take additional taurine and see how it goes.

    Though I’m no thyroid expert, this information may help someone: My friend who had gone hypo after eating way to much soy and raw brocolli, among other goitrogenic foods, and went all “health” nuts and stopped any iodized salt. To reset herself, besides changing her diet, she walked min. 5,000-8,000 steps a day. 10,000 steps per day would be ideal.

    There’s a lot of chatter on the benefits of coconut oil and hypothyroidism. Mercola has some articles too. I like it because my brain is un-fogged.

  25. Did the studies measure Iodine status? Could this be a ratio problem instead of a single nutrient issue? For example Chris Masterjohn has done a great job explaining the interaction of A, D & K2. Paul Jaminet recommends taking selenium with iodine. I would love it if someone could crunch the data from the study and figure out if Iodine deficiency explains the results.

  26. My do had me start 200mg of selenium back in Oct. There was 100 in my multi and then I take additional 100. After reading this should I think I will just take my multivitamin. These supplements drive me crazy. My antibodies were a little high when he tested. I have problems with pressure uticaria which is obviously caused by some underlying inflamation. Haven’t gone paleo but am gluten free. I wish I could see you Kris. You are so knowledgeable on thyroid.

  27. The study that showed increased risk of high grade prostate cancer, did it use selenamethionine? That could be the problem with supplementation in that case. Not all selenium supplements are created equally. I actually think selenium supplementation with methylselenocysteine is safer than Brazil nuts, which contain their selenium in the selenomethionine form (as I understand it)

  28. The importance of selenium in fighting colon also should not be overlooked. Definitely not something you want to be low in.

      • Selenium is one means to an end – thyroid nutrition and thyroid optimization – which in turn decrease cancer risk. Thyroid has a lot to do with proper cell differentiation, which is impaired in cancer. So an optimized thyroid and proper cell differentiation are the goals, not trying to ward off cancer with selenium. Individual selenium needs and tolerance vary widely.

  29. It is often recommended that Hashi patients keep their iodine levels low to avoid aggravating the autoimmune process and via low-iodine diet and avoiding supplemental iodine. In this scenario, supplementing with selenium would likely tilt the balance in the direction of selenium excess, would you agree? If selenium were obtained through diet alone, how often would dietary sources need to be consumed, daily? several times/week? Thank You.

  30. I have been taking Selenium supplements since 2005 when I was diagnosed with Hashimotos. My TPO anti-bodies have remained static throughout at around 900. Could be malabsorption due to Crohns…. I take 200mcg daily on an empty stomach ! Haven’t seen Brazil nuts here in Greece !

  31. It’s good to get these updates.
    My understanding is that the upper limit for selenium (RDA) is 400 mcg/d. So if you are taking a supplement of selenium of 200 mcg/d (to counterbalance iodine supplements from seaweed), would you need to be concerned about getting too much selenium?

    I would rather get the selenium I need from food sources too but have major digestive problems.

    Brazil nuts that I’ve been able to purchase all taste/smell rancid. Plus I don’t digest nuts well. Yes there are lots of other food sources of selenium. Just that I’m trying to help my Hypo thyroid using fucus seaweed for the iodine (and other minerals and trace elements). Taking the selenium supplement based on your articles about here about the protective feature of selenium for increased iodine consumption.

    In the article about it was stated: “selenium supplementation of 200 mcg/d increased the risk of high-grade prostate cancer”…..therefore it may not be so good to take supplemental selenium in the long term. So why is taking a supplement of 200mcg of selenium not so good, yet eating 1-3 brazil nuts (about 200mcg of selenium) is recommended instead? (the amount of selenium being about the same)

    • You might like to try Wilderness Family Naturals’ soaked and dehydrated Brazil nuts to see if they seem better to you than the ones from your other sources.

  32. I think the amount of selenium in Brazil nuts is related to how selenium-rich the soil was that the nuts were grown in. My understanding is that Brazil nuts can be a good source of selenium, but they are not guaranteed to be, depending on their source.

    • Yes, soil composition is critical, but if all other variables are equal, brazil nut have far-and-away the most selenium, you just need 2 or 3 nuts a day. I think of them as giant chewable tasty selenium supplements.

      • Brazil nuts are the second largest export from Peru/Brazil based on nut and seed, agricultural export The jungle soil is rich in selenium. The Brazil nut trees are NOT cultivated crops because it takes as long as 30 years to produce their first seed pods. These pods are the size of grapefruit and contain 12 to 25 nuts with their own hard coating/shell. The fruiting trees are very tall, 100 to 130 feet and can fruit for 300 years or more. No soil additives, no pesticides are used and harvesting is very difficult and dangerous work. Just take a look on Google what these monster trees look like. I’ve live in Peru for the better part of 30 years and there is not going to be a wide range of difference in selenium found in Brazil nuts from Peru or Brazil because there is a limited number of social groups that go into the jungle and harvest them It is not done by large corporations, although some large corporations do end up purchasing, pack, transport and export these nuts across the globe.

  33. I’m glad to read this article, because I wanted to start to take selenium supplementation. I bought 2 different types of supplementation bit somehow I didnt feel to take them. Finally I went back to the store and changed them to organic brazil nuts. Funny that I did it because I read the study a few days ago, and I thought that natural source would be better 🙂
    Chris thank you very much for verify that my decision was right 🙂
    Unfortunately my Anti TPO still high, although Im gluten-free for a year now. In Hungary where I live, most peope take medication for Hashi, and I pioneer here trying to solve the problem by dietary changes.
    Hopefully I will be the first healed person in Hungary! 🙂

    • You can get a food sensitivity test done, since you are already gluten-free. Are you 100% GF?
      As a physician i’d be concerned if my patient is not on Thyroid medication with abnormal Thyroid function reports & still high Thy antibodies. Do you have compounding pharmacies in Hungary? I recommend compounded T3-T4 combinations for my patients.No porcine thyroid for people with Thy antibodies. PLEASE do not take my recommendation as medical advise. “Curbside consults” can be dangerous & i dont normally do it 🙂

  34. Actually *one* brazil nut is quite adequate for the task of selenium supplementation for nutritional purposes. Most people are going to get their daily requirement of selenium 70 mcg by eating nearly any kind of diet, which you can prove to yourself by googling selenium content in foods and calculating selenium in a wide range of diets.

    Any mineral is going to be toxic in excess. What amounts to excess can vary somewhat with the individual.

    Some Hashi patients claim to be helped by selenium, others such as myself can be horribly aggravated by it. Some percentage of T3 is produced in the thyroid itself, the remainder is produced “peripherally” or in other parts of the body especially the liver. But in Hashi, when you stimulate the thyroid to “produce” with thyroid precursor nutrients and other thyroid stimulating substances such as ashwagandha or spirulina, antibodies can come out of the woodwork so to speak to attack the thyroid, producing inflammation, whereas antibodies don’t attack circulating thyroid from thyroid meds. I speculate that whether a Hashi patient is helped or aggravated by selenium supps may depend on how dead the thyroid is, what percentage of T3 is produced at the site of the thyroid vs. peripherally, and on constitutional types and genetics.

  35. Maybe there is a difference in response between persons having an inflammatory condition and healthy persons? In the study I link to below healthy men were fed a diet with 300 mcg selenium per day for 120 days and the end of the study their blood work indicated slight HYPOthyroidism, and in addition their sperm motility decreased (which is the main topic of the study. So even if it might be beneficial to supplement with higher doses of selenium for certain diseases, it might be wiser for healthy people to stick with the RDI recommendation of 50 mcg. However, the study is rather small, only 11 persons, so I don’t know how strong evidence that is. That’s your thoughts, Chris?

  36. Would cycling the selenium dosage be of benefit? Maybe 3 weeks on 1 off? As I understand it the amount of selenium can vary, not just by country or regions but even within a farm field itself. That Brazil nuts within a few hundred feet can have almost none to 200mcg per handful.

    • Yeah, this is why it’s unreliable to depend on Brazil nuts as a consistent source of selenium. You can try 3 a day as Chris suggests but test to make sure you’re getting enough!

  37. Brazil nut trees do no require selenium to grow. So, how can I tell if the Brazil nuts I am eating have any selenium in them? Oh, right, it’s on the package label.

    If there’s no selenium in the soil where the trees are grown, there is no selenium in the nuts. Otherwise, where would the nuts get the selenium?

      • Selenium is an inorganic mineral, not a vitamin.

        Perhaps you meant “vitamins and minerals,” but minerals are chemically quite different from vitamins.

        And, if I’m correct, they’re generally elemental and not something which the bodies of plants or animals can synthesize from other materials.

        Vitamins are complex structures generally consisting of many elements – carbon, hydrogen, oxygen, nitrogen, etc. – which are common in food and air.

        • In otherwords, the element comprising the mineral must be directly ingested, or absorbed through the skin, or what-have-you, to be within a living creature such as a plant.

        • You are correct. Minerals are “elemental” and cannot be manufactured via any biological process. Selenium is an element.

      • Except selenium is a mineral/element that gets created inside a star/sun. There is a finite amount of it here on earth and no plant or organism can create it only utilize it.

  38. I have given up on Brazil nuts as they very high in PUFAs.
    They always tasted of fungus (even the organics from Whole Foods).
    I’ll try my luck with seafood and the other foods mentioned.

  39. I tried going the Brazil nut route but unfortunately Brazil nuts are loaded with mold. Also, for many people with poor digestion, the nuts won’t be broken down adequately to absorb the selenium. I wasn’t able to get my selenium levels to normal with Brazil nuts (tested several times) until I supplemented. Something to consider.

    • Thank you for your input. I do a brief soak in hydrogen peroxide before the long soak for my brazil nuts, but I still notice that I don’t enjoy them like the other nuts and seeds that I also ate. Walnuts, pecans, almonds, sunflower all came out crunchy and delicious after dehydration. Brazil nuts continue to suck probably due to rancidity and ‘maybe’ molds. In any event, after reading the feedback, I’m going to abandon brazil nuts once I’m finished with what I have and go on with natural selenium supplement.

  40. Interesting! I was never that worried about selenium… I was told that grass fed Alberta beef was a good source… so I’m glad to hear that’s likely correct. And I eat brazil nuts sometimes anyway, heh. 🙂

  41. Well, this explains the recommendation you made for me yesterday. I prefer getting selenium from food anyway. Thanks, Chris!

    • It appears that phytate does not inhibit selenium absorption—at least not according to this study in baby chicks.

      This study shows that Brazil nut consumption improves selenium status (presumably without soaking them; there is no mention of that in the study and I think it unlikely the participants did it on their own without instruction).

      This study found a similar result. A single consumption of large amounts of Brazil nuts improved selenium levels and lipid profiles of healthy volunteers.

      • Since you are hard to reach, I figured I’d post here:

        Regarding Phytic Acid:

        A diet rich in vitamin C and carotenoids — which kale, brocolli, tomatoes, whole fruits, yams, carrots, peppers have in abundance — studies show that eating foods rich in these nutrients prevent the inhibitory effect of phytic acid on iron absorption. It’s HIGHLY likely other nutrients as well are getting absorbed just fine too. It appears that phytic acid is an anti-nutrient in diets low in vegetables and whole fruits. Sugar’s horrible effects on gut microbes doesn’t help either.

        I found the information about phytic acid on Weston A. Price’s site in an article “Living with Phytic Acid” way, way, way, way down on the page. This, of course, doesn’t mean that preparing your beans and seeds by soaking them, sprouting, fermentation is not beneficial, but in the context of a diet rich in the supporting nutrition, it’s not that big a deal.

        Off topic, but regarding RAE to A conversion which you might find interesting. The ability to convert RAE to Vitamin A varies from individual to individual. Some people are excellent at it and some people are not. Adding fat to a meal greatly increases absorption. Besides the fat, so one can get more carotenoids to work with, the RAE to A conversion requires bile acids, iron, riboflavin, niacin, and zinc. Bile acids are affected by many factors, one is fructose sans whole fruit. So many people, vegans included obviously, fail to get the supporting nutrition in their foods and also have a very sugary lifestyle.

        I’m an avid reader of your work, Westion A. Price, Chris Masterjohn, and other nutritional information outside of my vegan diet — my personal one. I’ve casually studied failed vegans. Their go to food after ending that diet is predominately fish, fatty fish. I observed Pacific Northwest vegans who were thin (too thin in my opinion), tired, poor teeth, brain fogged, dry skin, and so forth, however the vegans in Florida are rather healthy. Fat + sunshine and absorption and conversion are dramatically increased in a lifestyle that is fairly active and doesn’t not indulge in too much sugar.

        I’ve noticed that the vegans who are healthy after decades doing this, were not the ethically, environmentally, or health motivated ones, they are the ones with greater empathy for animals. I’ve noticed the “in-your-face” ones on an ideologically soap box fail more often, which I refer to as the “spiritual foot in your mouth” or “the universe doen’t appreciate rigidity” syndrome. The Tao flows.


        Iron absoprtion in man: ascrobic acid and dose-depended inhibition. American Journal of Clinical Nutrition. Jan 1989. 49(1):140-144.

        Rice and iron absorption in man. European Journal of Clinical Nutrition. July 1990. 44(7):489-497.

        Layrisse M and others. New property of vitamin A and Bcarotene on human iron absorption: effect on phytate and polyphenols as inhibitors of iron absorption. Archivos Latinoamericanos de Nutricion Sept 2000 50(3).

      • hello chris
        this is maryum,i have TSH levels high 7.5,uIU/ml,i am a female of 37 yrs almost ,my gut also weak,i pass WBCS in urine ,have recurrent UTI,i also have clots during monthly LDL increased,please help and which medicines should i use,plz contact me on my email.

    • Ben, can you provide any information on your source that Brazil nuts can’t be soaked? Incidentally, Wilderness Family Naturals sells organic Brazil nuts that have been soaked and dehydrated at low temperatures and they are delicious. They recommend refrigeration.

      • Yes, me too! I soak them ~24 hours, dumping the water half-way through. and then dehydrate on low temp for ~24 hours. Fantastically sweet.

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