Selenium is crucial for normal thyroid function.
In fact, if you have undiagnosed selenium deficiency, it could be making your thyroid function worse.
If you have chronic digestive issues, there is a good chance that you have inadequate selenium levels.
Selenium is especially important if you have an autoimmune thyroid disease such as Hashimoto's or Grave's Disease.
In this article, I will discuss selenium deficiency and the thyroid, how to know if you are selenium deficient, give you some great food sources of selenium, and discuss how and when you should consider using a supplement.
Let's get started...
Bear with me as I quickly describe the science behind selenium and its important role in the body.
Selenium is required for the proper function of some proteins in our body called selenoproteins.
These proteins perform many important functions in the body including:
- Conversion of T4 to T3
- Production of antioxidants
- Energy productions and metabolism
Let's discuss some of these functions in a little more detail:
Selenium is required for the optimal conversion of T4 into T3 in the peripheral tissues.
Selenium is needed for the proper function of the deiodinase enzymes which perform the conversion process.
As a quick reminder, the thyroid gland produces primarly T4, which is a thyroglobulin molecule with 4 iodine molecules attached to it. This is the transport form of thyroid and is mostly inactive.
In order for the body to be able to use the thyroid hormone, an iodine molecule must be cleaved off of the T4 by the deiodinase enzyme, which converts it into T3. T3 is the active thyroid hormone.
Having a deficiency of selenium does not in itself cause illness.
It appears instead that being deficient in selenium just makes us more susceptible to illnesses due to its role in normal immune function.
In other words, having an optimal selenium level helps to ensure that our immune system is working at its maximal level.
This is because selenium plays a huge role in increasing antioxidant levels in the body.
In fact, selenium supplementation has been shown to improve immune function in patients that were deficient.
Iodine is a controversial issue in regards to thyroid health.
There is plenty of evidence that shows that low iodine is a huge cause of thyroid disease worldwide.
However, there is also evidence that excessive iodine can also damage the thyroid gland and may even increase the incidence of autoimmune thyroid disease such as Hashimoto's.
One study showed that taking iodine in the presence of LOW levels of selenium may actually increase your risk for thyroid tissue damage.
Conversely, if you supplement with selenium in the presence of low iodine levels, it can also worsen hypothyroidism.
It appears that iodine is dangerous to the thyroid ONLY when selenium levels are low or high.
Optimizing the selenium level allows the thyroid to tolerate a wide range of iodine levels.
The selenium appears to protect the thyroid from iodine at least in some part because it increases regulatory T cell levels.
What if you have Hashimoto's?
I believe the evidence shows that it is okay to take iodine if you have Hashimoto's as long as you are also supplementing with selenium.
Selenium deficiency doesn't necessarily cause any obvious symptoms, but there are some signs to look for that can indicate that you may be low.
Let's discuss some of the big ones below:
Selenium deficiency is common in patients that have chronic digestive issues such as Crohn's disease, Celiac disease, etc.
This is felt to be due to malabsorption caused by the inflammation that is occurring in the gut.
Selenium deficiency is commonly associated with vitamin B12 deficiency because they both are affected by poor gut absorption.
So if you have B12 deficiency or any type of chronic gut inflammation, there is a strong chance that you are deficient in selenium.
As I discussed earlier, selenium is important for the conversion of T4 to T3.
When that conversion process is reduced, the free T4 levels will begin to rise and the free T3 levels will begin to fall.
To make matters worse, if you go see your doctor and he or she only checks your TSH and T4 and not your free T3 level, it will look like your thyroid levels are "normal" or even "high."
Meanwhile, your hypothyroid symptoms continue to worsen because you are low in active thyroid hormone.
Not a good situation at all.
That's why it is critical that you find a doctor that will check a complete thyroid panel and will listen to you and your symptoms, and not solely depend on lab results to manage your thyroid problem.
Let me start with an obvious statement: Not all hair loss is caused by selenium deficiency (you've seen my photo and my selenium level is good!).
However, selenium deficiency has been shown to cause changes in hair.
It also can cause your nails to get brittle and crack easily.
Replacing low selenium levels has been shown to improve hair growth and nail growth.
If you suffer from unexplained hair loss or brittle nails, you should consider getting a further workup.
At a minimum, you should look at these micronutrients as possible culprits: iron, zinc, selenium, and biotin.
You should also get a complete thyroid panel.
There is a lab test to measure the selenium level in the body, specifically in the red blood cells.
It is called an RBC Selenium Level.
I do not routinely check this on patients. If I suspect a selenium deficiency, I start treatment.
However, if a patient continues to have signs or symptoms of selenium deficiency, it can be checked to make sure they are absorbing the selenium from their food or supplements.
So if you think you have a selenium deficiency, what should you do about it?
Selenium is a micronutrient, meaning only small amounts are needed.
It can be replaced in your body either through increasing your consumption of foods that are high in selenium and/or by taking a selenium supplement.
Without a doubt, it is always safest to use food to increase nutrient levels in our body.
Most Americans eat so poorly that simply improving their diet can do wonders for helping them to regain their health.
The food with the highest amount of selenium is brazil nuts.
Eating 2 brazil nuts per day will increase your selenium level as much as 100mcg of selenomethionine.
Other foods with good selenium content include:
It's always best to start with natural food sources such as these.
However, that is not always possible.
For instance, I am personally allergic to brazil nuts and I don't have a big fondness for fish (unfortunately). Therefore, I use a supplement periodically to keep my selenium level optimized.
When using supplements, it is always critical to use a good quality supplement from a respected company that uses quality control standards when making their products.
My preferred brand for supplementing selenium is below:
Why I Like It
May reduce antibodies in patients with Hashimoto's
Also acts as an anti-inflammatory
May help reduce anxiety symptoms
Helps boost T4 to T3 conversion (helpful in those with high reverse T3)
Who Should Use It
How to Use
My Recommended Brand and Product
I prefer selenomethionine because of it's high bioavailability.
I typically recommend supplementing for only a few months (3-6) which should restore the levels in the body to the optimal range.
Like most things, you can overdo selenium supplementation as well.
Excess selenium can cause a variety of symptoms, including GI upset, white blotchy nails, hair loss, fatigue, irritability, and mild nerve damage.
One study even showed a possible increased risk of prostate cancer in patients with excessive selenium.
Once you have repleted the tissues and changed your diet, continued supplementation should be unnecessary.
The only exceptions would be if you have poor absorption from chronic digestive tract conditions such as inflammatory bowel disease, IBS, Celiac diease, etc.
Selenium is a vital micronutrient for normal thyroid function, immune system function, energy production, and metabolism.
Selenium deficiency is common but can be difficult to diagnose.
It is always best to treat selenium deficiency by eating food rich in selenium.
If that isn't possible or if you have absorption issues due to chronic GI issues, adding a good quality selenium supplement may be necessary.
You should not take a selenium supplement indefinitely. Usually taking it for a few months is sufficient unless you have a chronic GI problem.
If you have a selenium deficiency, it is also important to look for other micronutrient deficiencies such as iron, zinc and iodine.
Now it's your turn...
Do you think you have a selenium deficiency?
What have you used to treat it. Has it helped?
Leave your comments below.
Dr. Whelchel is a family physician who specializes in functional medicine, especially hormone optimization. He has over 20 years experience in private practice managing patients with various medical issues. His passion is helping patients reach their full potential of wellness and quality of life. He grew up in the Texas Panhandle where he currently lives. He is married and has 3 awesome children.