This article is part of a special report on Thyroid Disorders. To see the other articles in this series, click here.
A healthy thyroid is a critical component of one’s overall health, and many people are struggling with thyroid disorders such as hypothyroidism, specifically Hashimoto’s autoimmune thyroiditis. In this autoimmune condition, the immune system attacks the thyroid gland, with the resulting inflammation leading to an underactive thyroid gland or hypothyroidism. Hashimoto’s disease is the most common form of hypothyroidism and was the first condition ever to be classified as an autoimmune disease.
I’ve written extensively about thyroid health, focusing on a multitude of environmental factors that may affect thyroid function, including gluten, gut health, stress, excess iodine, and vitamin D deficiency. I’ve also discussed why dietary changes are always the first step in treating Hashimoto’s, and why replacement thyroid hormone is often necessary for a successful outcome.
There Is yet Another Nutritional Factor That May Play a Role in Thyroid Health: Selenium.
Selenium deficiency is not thought to be common in healthy adults, but is more likely to be found in those with digestive health issues causing poor absorption of nutrients, such as Crohn’s or celiac disease, or those with serious inflammation due to chronic infection. (1, 2) It is thought that selenium deficiency does not specifically cause illness by itself, but that it makes the body more susceptible to illnesses caused by other nutritional, biochemical or infectious stresses, due to its role in immune function. (3) Adequate selenium nutrition supports efficient thyroid hormone synthesis and metabolism and protects the thyroid gland from damage from excessive iodine exposure. (4)
One study found that selenium supplementation had a significant impact on inflammatory activity in thyroid-specific autoimmune disease, and reducing inflammation may limit damage to thyroid tissue. (6) This may be due to the increase in glutathione peroxidase and thioredoxin reductase activity, as well as the decrease in toxic concentrations of hydrogen peroxide and lipid hydroperoxides which result from thyroid hormone synthesis. (7)
Another study followed patients for 9 months, and found that selenium supplementation reduced thyroid peroxidase antibody levels in the blood, even in selenium sufficient patients. (8) While these studies show promise for the use of selenium supplementation in preventing thyroid tissue damage, further research is needed to determine the long-term clinical effects of selenium treatment on inflammatory autoimmune thyroiditis.
Additionally, selenium is also essential for the conversion of T4 to T3, as deiodinase enzymes (those enzymes that remove iodine atoms from T4 during conversion) are selenium-dependent. As I’ve explained before, T3 is the active form of thyroid hormone, and low T3 can cause hypothyroid symptoms. A double-blind intervention study found that selenium supplementation in selenium deficient subjects modulated T4 levels, theoretically by improving peripheral conversion to T3. (9) In cases of severe selenium deficiency, conversion of T4 to T3 may be impaired, leading to hypothyroid symptoms. As T3 conversion is not performed by the thyroid, the dependence on selenoproteins for this conversion demonstrates how significant selenium deficiency could lead to hypothyroid symptoms.
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So the Question Is, Should You Start Supplementing with Selenium If You Have Hypothyroidism, Hashimoto’s Thyroiditis, or Low T3 Levels?
As the answer often is, it depends.
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. (10) 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.
Moreover, a large clinical trial examining the effects of selenium supplementation on prostate cancer risk in over 35,000 men found that those with normal to high selenium levels at baseline experienced a significant increase in the risk of prostate cancer after supplementing with 200 mcg/d of selenium. For more details on this study, see my article “Important Update on Selenium Supplementation“.
For now, the best option for most people may be to include selenium-rich foods in the context of a healthy Paleo diet. Great sources of selenium include: brazil nuts, crimini mushrooms, cod, shrimp, tuna, halibut, salmon, scallops, chicken, eggs, shiitake mushrooms, lamb, and turkey. Brazil nuts are particularly rich in selenium; it only takes one or two per day to improve your selenium status and boost immune function. (11)
Making sure your selenium intake is optimal may give your immune system and thyroid the boost it needs to help it function better. It is especially important for those managing thyroid conditions to ensure their selenium status is adequate.
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Fantastic article…thanks Dr. Kresser…wish I had seen it when it first come out!! I recently started eating several Brazil nuts a day and am feeling so much better. I have come a long way in healing my thyroid by changing my diet over the last 5 years in accordance with the Weston Price Foundation. Most of my symptoms have gone away but still struggle with low energy and a little brain fog (neither as bad as before). I am so excited to be feeling so well these days; before the Brazil nuts I felt that I had hit the ceiling and could not get any better since I had implemented everything I knew to do. The number of Brazil nuts I eat has varied from 4 to 8…dont’ really know how much I should eat while trying to make up for my deficiency. Can anyone tell me how many I should eat daily and how long will it take before I change to eating just 2 per day as a maintenance level. Also, I don’t want to mess up a good thing…so now, I don’t know if I should add a little kelp for iodine to my kefir smoothies or just continue eating Brazil nuts daily. I appreciate any help in this matter!!
BTW, my last thyroid results: TSH—- 0.85 (0.34 – 4.82 reference range)
FT4—- 0.75 (0.77 – 1.61 reference range)
My daughter has a heterogenous thyroid, and her antibodies were highs few years ago, but since then have been normal. She also has a gluten intolerance.Doctors say to keep an eye on things and that she has potential to develop Hashimotos.
She is living near a nuclear plant located (within 5 miles.) I worry about any excess radiation from plant. Should she be supplementing with iodine and selenium, or just selenium?
I have been hypothyroid for about 18 years. For years I was on Synthroid, then Levoxyl. I’ve been on Armour for a few years. A year ago I felt like I crashed- no energy, no appetite, overwhelming fatigue, etc. My naturopath put me on additional T3, increasing it every few weeks. Two months later I felt like a new woman, so I maintained the 90mcg of T3 with my one grain of Armour. Then I had a Rbc elements test that showed I was low in selenium and iron. I started taking 200mcg of selenium right away, and after further testing I added iron. Although this is not necessarily related to my thyroid, I have had warts in my hands for several years and I have tried practically everything to get rid of them. I was still getting new ones, and I had so many already. After a couple of weeks on the selenium, the warts just started disappearing. It did take six months for the last one to go away, but they are all gone.
I was taking my temperature every day before I started the selenium, and after adding the selenium my morning temp went up almost every day until it was a degree higher than before, and then it leveled off about 3/10 of a degree lower than the hi point.
Also, I had my TSH, T4, T3, Reverse T3 checked in July and the results showed I was not converting any T4 to T3. We did the tests again in December, and there was great improvement and we are lowering my added T3. It appears that the improvement in my thyroid levels is due to the selenium, and possibly the iron as well, since those are the main changes I made during that time. Best of all, I feel better now than I have in a long time. I sleep better, and I feel as though my sex hormones are balancing out even though I haven’t supplemented hormones.
Iron is a required co-factor. If you don’t have enough iron in your blood, your thyroid medication can’t work effectively. However, do not take iron within 4 hrs of oral thyroid meds.
I take my T-3 sublingually, which means I can take iron at the same time. Different pathways.
Also, be careful of the type of iron you take.
Dear Chris. I am 26 years old and have an 8 month old baby. My thyroid completly crashed after his birth and it took doctors 6 month to figure out my t4 was at 5 and my tsh was so high it did not register on the chart. I was experiencing kidney pain, swelling in the throat,horrible body pain, hair loss, major digestion problems,bleeding, memory loss, and extreme fog brain. I am only on synthroid .125 and slowly am on the mend. They recently ran the hashimotos test and i am positive. I still feel as though i am going from hypo to hyper depending on my cycle. It is very hard and i am at my wits end. Any help from anyone is appreciated.
I have recently been diagnosed w Hashimotos .. Numbers showed in the 800’s so it la high but the doctor as she has seen higher and mine may be a result of childbirth and should correct itself. I have bone/muscle pain and fatigue and coldness. I have decided to take a thyroid helper along w daily energy multiple vitamin. I have yet to try iosol iodine drops. Am I on the right track w this? Since I have taken the two minus the iosol drops my brain fog is lessened tremendously and I don’t ache as bad.
Great info, thank you. I’m 5 months postnatal with significantly elevated TSH and enlarged thyroid. Is selenium and or iodine supplementation a good idea (am breastfeeding) or should I just let things settle (as I’ve been advised)? I’m receiving conflicting information. Have never taken either before (just thyroid meds) as my Hashimotos usually very stable.
Thanks for the article. Selenium supplementation had some unexpected effects for me. I have been fighting with very low energy and mental sluggishness for the past 1.5 years. My TSH is in the *normal* range (3.8) but I finally found out that my antibodies are too high (TPO 267). I started Selenium 200 mcg per day and immediately felt great. My energy levels are pretty much optimal now and the brain fog has lifted completely. I have been on it for 4 weeks and am very happy with the way I feel. My only problem is that we’re trying to get pregnant and the selenium seems to have a negative impact on my menstrual cycle. It shortened my luteal phase from 12 days to 9 days, delayed my ovulation from day 15 to day 20, decreased my basal body temperature from 97.1 – 97.3 (pre-Ovulation) to an 96.7-96.1 degree. I also seem to gain weight (despite eating healthy and doubling my exercise thanks to the new energy boost). Does selenium affect progesterone and estrogen levels? Thanks.
Thanks for the article. Selenium supplementation had been good and bad for me. I have been fighting with very low energy and mental sluggishness for the past 1.5 years. My TSH is in the *normal* range (3.8) but I finally found out that my antibodies are too high (TPO 267). I started Selenium 200 mcg per day and immediately felt great. My energy levels are pretty much optimal now and the brain fog has lifted completely. I am very happy with the way I feel. My problem is though that we’re trying to get pregnant and the selenium seems to have a negative impact on my menstrual cycle. It shortened my luteal phase from 12 days to 9 days, delayed my ovulation from day 15 to day 20, decreased my basal body temperature from 97.1 – 97.3 (pre-Ovulation) to 96.7-96.1 degree. I also seem to gain weight (despite eating healthy and doubling my exercise thanks to the new energy boost). Any insight in why that might happen? Does selenium affect progesterone and estrogen levels? Thanks.
If I take 200mcg a day, how long will it take to build up in my system? will it take months or what? and also, if I take it for about a month straight then take off for a few days, will that be okay? will it still build up?
Hi- very good info here, I have a goiter and Hashi’s. My doc said all was ok, she would not treat with anything at this point. My main struggle is sleeeeeep!! I am a very easy going person but have terrible panic attacks and rapid heart beats mostly just at night and very poor sleep. I recently cut out gluten, but it seemed to make my symptoms worse? I have taken iodine (big mistake) and suffer for days until it gets out of my system. Will check into a naturopath this week, any thoughts?
Thanks for the response. Do you feel the same way for someone who already is hypothyroid and has a history of heart disease??? He, too, is eating one Brazil nut/day and wants to know if this is problematic for someone like him…
I don’t think it would be problematic for him either.
OMG this is sooo complicated. From one reply to the next, each with differing stories, symptoms, differing supplements, dosages and differing success! I was diagnosed with what they called Fibromyalgia in 2001 and this year through my research stumbled onto the possibility that it might be my thyroid and sure enough was diagnosed with Hashimotos. Can a girl get a straight answer? I’m about to give up! Too much selenium and I could gain weight and lose my hair. Severe pain, fatigue and brain fog for years has stolen my life and career. It is unbelievable to me that this should be sooo complicated… 🙁
Hi Chris,
In this article, you mentioned that “For those concerned with the high level of omega-6 fats in brazil nuts, it may be worth considering the fact that it only takes one or two brazil nuts per day to improve your selenium status and boost immune function.” As a result, I encouraged each of my family members to eat ONE brazil nut/day as a way to support their thyroid health. Today in your Beyond Paleo series, you said, “Selenium is plentiful in organ meats, ocean fish, and in brazil nuts. One brazil nut contains 100 mcg of selenium, but it also contains a whopping 1 g of omega-6 linoleic acid, which as you know from previous articles in the series, we want to limit significantly. This is why I don’t recommend brazil nuts as a source of selenium. Ocean fish are also good sources of selenium. 100 g of cod contains about 150 mcg.”
This statement says you DON’T recommend brazil nuts as a source of selenium.
Has your stance changed? Should we not be consuming even one/day?
I have a friend who is hypothyroid. Should he be consuming them as well?
Please help!!! I respect your opinion and advice and am in need of some clarification.
My stance on omega-6 in whole foods like nuts has changed somewhat. I don’t think a single brazil nut a day is problematic. That said, ocean fish is a superior source.
Thanks for your prompt reply. Do you have contact information for him? Thanks!
I’d post a comment on his blog: http://perfecthealthdiet.com
Thanks–that’s what I did. 🙂
My question is this: what should be done to reverse (potential) selenium toxicity? I am not sure, but I *think* eating too many brazil nuts (I guess around 4-8 daily) might explain my alarming hair loss (handfuls after each shower, lots on the pillow in the morning). I have been losing hair for about a year, but recently it starting coming out in handfuls, and fairly recently I have discovered I like brazil nuts (last 5 months or so?). My thyroid reads normal (talked to neuro, ob/byn and dermatologist–all clueless). I normally take Rebif for relapsing remitting MS (although I have been off rebif for about 4.5 mos)–neuro says it’s not rebif. I recently (1.5 mos ago) suffered a miscarriage–ob/gyn & dermo say that this could cause rapid hair shedding, but my hair has been falling out long before I was pregnant. No one has asked me about selenium supplementation or eating brazil nuts–came to that on my own (I am a big fan of your site Chris and about 90% paleo most of the time). Let’s say it is the brazil nuts. If I stop eating them (well, when, as in right now!) will my hair loss subside/grow back? Anything is particular I should be doing along with stopping the nuts? Thanks!!
You might want to contact Paul Jaminet about this. He knows more than I do about overcoming selenosis.
It may also be a coincidence that the hair loss is increasing with brazil nut consumption. Don’t discount nutrient deficiencies like biotin, Bs and trace minerals like silica.
Also thyroid conditions are well known to cause hair loss – there is no such thing as “normal” when it comes to thyroid results. It’s likely the doctor only checked TSH which is pretty much useless in isolation. I suggest finding a functional medical practitioner who will order the right thyroid tests and knows how to interpret them!
Good luck 🙂
Thanks, Allison. I assuming I can find (and afford) and functional medical practitioner, what are the right thyroid tests? I take a B complex several times a week (mostly daily) but I don’t know anything about silica (and therefore don’t know how or if I get it).
Hi Heather,
Where are you located? There are some listings like on this site that should help:
http://thyroid.about.com/gi/o.htm?zi=1/XJ&zTi=1&sdn=thyroid&cdn=health&tm=9&f=00&tt=14&bt=0&bts=0&zu=http%3A//www.thyroid-info.com/topdocs.htm Also, the site realthyroidhelp.com has a forum where the moderators keep a list of recommended doctors.
Thyroid testing should include TSH, Free T3 and Free T4. Additionally, thyroid antibody testing is useful (esp if there is family history or a suspicion of an autoimmune component – if you have MS then it is possible/not uncommon to have more than one autoimmune disease). Reverse T3 is also useful though many doctors won’t run this.
Silica is a trace mineral. You can get this in a good trace mineral supplement – the soil is generally quite deficient in trace minerals as farmers don’t replace the minerals in the soil after each crop is done (organic farmers do as far as I know). Here is some more information: http://www.lef.org/magazine/mag2003/apr2003_report_silicon_01.html
Re B vitamins, try to find one that has the active forms of B vitamins included, as many people have trouble converting the forms in supplements into the form actually used by the body’s cells. AOR make a really good one: http://www.iherb.com/Advanced-Orthomolecular-Research-AOR-Advanced-Series-Advanced-B-Complex-90-Veggie-Caps/33062
I lost lots of hair on selenium, stopped that , took biotin & vit e, all is good!!
I have been eating one Brazil nut per day. Never diagnosed with low thyroid, but my mom has it and I have been very low on energy, low tolerance to cold, thinning hair. I bet it is border line. Ever since I have been eating this high selenium rich food, I have noticed my energy levels and body warming levels are UP! My mom swears by it too…no meds for either of us. Dont eat more than one or two nuts a day, you can overdose on selenium.
I have a tsh at .03 everything else is normal range, dx of discoid subacute contanieous lupus, ana tested under 1000, sx include racing heart, lethargy, weight gain, brain fog to name a few.
Julia,
You could be hyperthyroid or be in a hyper phase of Hasimoto’s. Did you and have your thyroid antidoies tested for TPO, TGB and TSI? They will help you determine if you have hyperthyroidism, or are in a hyper phase of Hasimoto’s thyroiditis.
I have thyroid antibodies for hypo at 161. I read a blog about selenium and have been taking it. I am extremely worried now because I have taken about 17,000 mcg within 2 weeks. Then I read about it being bad for thyrid if you arelow in iodine. I think I have taken way too much because I’m desperate to feel better! Pleaseeee help me. What do I do? Not take any for a few days and only take one a day from now on?? Please help. I really appreciate it!
Selenium can be toxic at high doses. Please do not exceed 200 mcg per day in the supplemental form. I would stop for at least a couple of weeks before continuing. Iodine can be problematic for people with Hashimoto’s if they are selenium deficient and/or they take too high of a dose too quickly. I would get back on selenium for a few weeks before attempting to take iodine, and if you do take iodine, start with a very small dose (i.e. 200 mcg) and build up very slowly.
How to get in touch with Paul Jaminet?
I started taking synthroid 25 mg and then upped by my doc to 50 over a 5 month period. I have Hashimotos. he always recommend high dose D, and I am taking that but then he recommended Selenium OTC and a week after starting it, I started havign severe headaches, and neck and joint pain.
My stomach was upset too. and several other negative side effects mentioned in articles about Selenium pills (not the stuff found in foods). I stopped taking the Selenium and called my endocrinologist !!!! I eat all the right foods for taking in Selenium, and will never take Selenium again!
Hi! Great information! I had a full hysterectomy 5 years ago and have been taking bio-identical hormones for the last 1.5 years. My pharmacist is in the process of eliminating all estrogen from my hormones and also from my diet. I do eat very clean and exercise regularly. I struggle with losing weight. Cannot budge a pound. My doctor mentioned that it could be my thyroid, and even though my levels may show normal it could still be presenting the problem. I am tired alot, and also have foggy brain. I was told that taking selenium and iodine may help reduce these problems. If that is the case, how much should I take daily and how long before I know that is helping or not???
Could you have poor absorption while taking Metformin. I take both synthyroid and Metformin for hypo and pcos. I know Metformin inhibits absorption of some fat and sugar but what about nutrients