Selenium: The “Protector” Trace Mineral

Selenium is named after the Greek word for moon, “selene”.

Selenium’s namesake is more poetic than descriptive though because it can be found naturally right here on Earth. In fact, selenium is everywhere: in the air, water, land, and in all living things.

And it’s critical for the health of all living things— human beings included! Selenium is an essential trace mineral with incredible antioxidant properties. It protects cells from damage, and as you’ll see in just a moment, this has some big implications for bone health.

What’s more, getting the right amount of selenium could be the difference between bone loss and bone gain. But don’t worry, because we’ll cover exactly how much selenium you need, where to get it, and more below. First though, let’s talk benefits!

How Selenium Benefits Your Bones

Slows Bone Loss and Supports Bone-Building

Selenium plays a powerful dual role when it comes to bone health. It both lessens the activation of osteoclasts (cells that break down bone), and supports the creation and activity of osteoblasts (your bone-building cells)!

So how does it work? Well, selenium is what we call a co-factor, a substance that activates an enzyme. And in simplest terms, enzymes bring about changes in the body.

Now, selenium is a co-factor for some of the body’s most important antioxidant enzymes. As you may know, antioxidants protect cells from oxidative stress. And oxidative stress is when uncharged molecules called free radicals attack the body’s cells.

So selenium is required for a group of 25 antioxidant enzymes to work. These enzymes are called selenoenzymes, and they perform many critical functions.

Here, we’ll cover how selenoenzymes both slow bone loss and support bone-building:


  • Your bone-building cells make their own selenoenzymes which they use to protect themselves from attack by free radicals. Now, it’s important to note that even healthy cells are constantly fending off free radical attacks.

    This is because all cells need to produce energy within themselves to function. But when cells create energy, they also produce free radicals. So, it falls to selenoenzymes to fend off these naturally occurring attacks!

    In other words, selenoenzymes neutralize free radicals, and prevent them from damaging your bone-building cells.

  • When free radical attacks aren’t stopped, the damage they cause results in the production of more free radicals. It’s a vicious cycle, and it promotes bone loss in several ways.

    One of these ways is that free radicals mess with the development of new osteoblasts from their precursor cells. Precursor cells are one step away from becoming bone building cells. But they can only take that final step if they protect themselves from free radicals.

    Once again, these cells need selenoenzymes to raise their defenses. And the only way for them to produce selenoenzymes is if they have enough selenium. So, without adequate selenium these cells will never turn into osteoblasts.

    The result? The bone remodeling process becomes unbalanced, and you begin to lose more bone than you build.

  • Perhaps the most critical antioxidants for our bones require selenium to work. So, that makes them selenoenzymes! These particular selenoenzymes are called glutathione peroxidases. But to keep things simple, we’ll just call them GPs.

    Now, GPs protect your bones in two ways:

    What’s more, GPs are responsible for neutralizing a dangerous free radical called hydrogren peroxide. And hydrogen peroxide releases a highly destructive free radical that triggers your osteoclasts (cells that break down bone)!  

    This mechanism is of particular interest because it– in part– explains why women are at risk of bone loss during menopause. You see, estrogen increases our production of a certain kind of GP. So when women lose estrogen, that GP drops, leading to increased osteoclast production and ultimately bone loss.

We’ve established how important selenoenzymes are for your bone health. Now, let’s look at some proof!

Several studies have confirmed that blood levels of selenium are related to bone health. These studies show that insufficient selenium levels equal increased bone loss and low bone mineral density (BMD). On the other hand, healthy selenium levels equal decreased bone loss and higher BMD!

The largest of these studies confirmed that selenium impacts bone loss and BMD and is highly likely to affect fracture risk!*

*Note that this was an observational study, meaning there was no active intervention. So, we can’t say for sure that other factors like lifestyle choices didn’t impact the results. More research will be needed to come to a definitive conclusion!

Here are the highlights from the study:

The Osteoporosis and Ultrasound Study (OPUS)

  • A 6-year prospective study (this kind of study follows a group of people over a long period of time).
  • 2,374 healthy postmenopausal women participated.
  • Researchers tested hip BMD and blood levels of selenium at the beginning of the study and at the 6-year follow-up.
  • Selenium levels on the upper end of normal were associated with higher hip BMD at the beginning and the end of the study.
  • Lower selenium levels were associated with higher bone turnover and lower BMD.
  • Researchers concluded that the data showed adequate selenium is required to maintain bone.

It’s important to mention that too much selenium can be toxic. But don’t worry, we’ll go over how much selenium you need for optimal health a little further down the page.


Supports Healthy Thyroid Function

You may know your thyroid gland is essential for bone health. It produces the thyroid hormones thyroxine (T4) and triiodothyronine (T3), and these hormones play a vital role in all sorts of functions including bone maintenance.

Now, your thyroid gland primarily produces T4 which is much less active than T3. In fact, it’s considered a “prohormone”. In other words, it’s the inactive form of a hormone that comes before the active version.

So, our active T3 is made from T4! But to do this, T4 needs the help of the deiodinase enzymes. Once again, selenium is required to activate these enzymes. Which means that insufficient selenium leads to low production of thyroid hormones or an “underactive” thyroid (a condition called hypothyroidism).

On the other side of this equation, selenium deficiency can also contribute to an overactive thyroid (hyperthyroidism)!

Let’s have a look at how too little selenium triggers these conditions, and how this affects your bone health.


  • Without selenium your thyroid gland can’t produce T3. This is a problem because our thyroid hormones regulate the rate at which our cells break down old bone and build new bone (the bone remodeling process).

    Now, your body breaks down old bone a lot faster than it builds new bone. To give you perspective, each bone remodeling cycle involves three to five weeks of bone breakdown. But it takes three months for osteoblasts to lay down new bone to replace the bone that was removed!

    So, when your thyroid hormones aren’t working properly, the whole remodeling process slows down. This means it takes a little longer to break down old bone, but it also takes a lot longer to build new bone. And unfortunately, this imbalance favors bone loss.

    As you can see, it’s a delicate balance when it comes to thyroid hormones. Too little activity (hypothyroidism) causes bone loss, but too much activity (hyperthyroidism) does too! So, let’s look at how selenium relates to hyperthyroidism as well.

  • It’s well known that hyperthyroidism causes bone loss. When thyroid hormone levels are too high (T3, in particular), the body goes into overdrive. And as we’ve seen, thyroid hormones regulate the bone remodeling process.

    Selenium deficiency can cause hyperthyroidism because of its relationship with the deiodinase enzymes. Remember, these enzymes regulate how much T3 is circulating in our bodies— not too much or too little.

    In other words, the deiodinase enzymes both activate AND deactivate thyroid hormones. So, if you already have too much T3, then not getting enough selenium means you won’t be able to regulate this excess.

    This sets off a negative chain of events for your bones. When your T3 levels are too high (hyperthyroidism), the bone remodeling process speeds up. And since it’s so much faster to break down old bone than it is to build new bone, the result is a net loss of bone.

    In fact, increased bone break down due to hyperthyroidism can cause a loss of around 10% bone mass per remodeling cycle. And your average bone remodeling cycle takes 24 weeks… So, that means you could lose as much as 20% bone mass in one year!

    You can see how this would quickly lead to reduced bone mineral density (BMD). So, maintaining the right level of selenium is crucial for healthy thyroid function and bone health.

    But don’t worry, we’ll cover what the right level of selenium is a little further down the page!


Helps Your Body Clear Toxic Metals That Cause Bone Loss

It used to be the term “heavy metal” conjured images of long hair, black eye makeup, and crowded music halls. Nowadays though, heavy metal has some more negative associations.

You may have heard of environmental toxins. These kinds of toxins can be found in our food, our cleaning products, our water supply… and they wreak all sorts of havoc on our bones.

What’s more, metals are some of the most harmful toxins out there! The good news is selenium can help protect you from these metals.

Now, many metals do damage by producing free radicals in the body. If you recall, free radicals are the perpetrators of oxidative stress. They attack the body’s cells and disrupt all sorts of bodily functions in the process— including the bone remodeling cycle.

This is where selenium comes in. Human studies show that selenium helps protect against free radical damage caused by metals. It does this through selenoenzymes that combine with toxic metals and basically deactivate them.

So, selenium protects against bone loss by getting rid of toxic metals that cause it!


Lowers Risk of Hip Fracture— Even in Smokers!

By now, you’re likely starting to see just how important selenium is for your bones. And when you consider 20-24% of people pass away within a year of suffering an osteoporotic hip fracture… this last benefit drives the point home.

Recent research shows that selenium helps lower the risk of hip fracture— even in smokers!

Now, we know that smoking is bad for your bone health (not to mention your overall health). So the fact that selenium reduces the risk of fracture in smokers says a lot.

Let’s take a look at some proof:

Selenoproteins and Selenium Status in Bone Physiology and Pathology

  • Researchers conducted a case-control study to find out whether there’s a link between antioxidants and osteoporotic hip fracture risk.
  • They also looked at whether smoking affected this link (note that smoking is known to increase fracture risk).
  • Smokers were divided into five groups based on how much selenium they received.
  • The group that received the most selenium had a 73% lower risk of hip fracture compared to the group that received the least selenium.

As you can see, there were significant positive effects of selenium intake on hip fracture risk.

And these results line up with what we’ve covered on selenium’s role in bone maintenance and protection!

How much selenium do you need?

So we’ve seen how crucial selenium is for your bones. But how much do you need?

Well, for healthy men and women aged 19 and older, the recommended daily allowance (RDA) for selenium is 55 mcg per day. But keep in mind that when the Institute of Medicine set this allowance, their goal was to prevent deficiency, not promote optimal health.

The Food and Nutrition Board of the Institute of Medicine also set a “No-Observed-Adverse-Effect-Level” (NOAEL) for selenium of 800 mcg per day for adults. But to account for sensitive individuals, they set the Tolerable Upper Intake Level (UL) at 400 mcg per day (half the NOAEL).

The dosage you’ll want to pay attention to though is 200 mcg per day. This is the typical dose used in clinical trials that show selenium’s health benefits, and that many nutritional supplements follow.

So, for optimal health (bone health included), 200 mcg a day is the intake you should aim for!

Best Food Sources of Selenium

As we’ve seen, selenium is a trace mineral… so, you’ll only find traces of it in food! That said, there are certain foods that contain more selenium than others. So here are some of the top “selenium-rich” foods to include in your bone-healthy diet.

Note: If you’re deficient in selenium, you may want to consider supplementation in addition to implementing some of these foods. We’ll explain what factors may cause a selenium deficiency after this table!

 

Best Food Sources of Selenium

Food Serving Size Amount in Micrograms
Brazil nuts 1 ounce (6-8 nuts) 544
Tuna, yellowfin, cooked dry heat 3 ounces 92
Halibut, cooked dry heat 3 ounces 47
Sardines, canned in oil, drained 3 ounces 45
Ham, roasted 3 ounces 42
Shrimp, canned 3 ounces 40
Beef steak, bottom round, roasted 3 ounces 33
Turkey, roasted 3 ounces 31
Chicken, light meat, roasted 3 ounces 22
Cottage cheese, 4% milkfat 1 cup 20
Rice, brown, long-grain, cooked 1 cup 19
Beef, ground, 25% fat, broiled 3 ounces 18
Bread, whole-wheat 1 slice 13
Bread, white 1 slice 6
Baked beans, canned, vegetarian 1 cup 13
Oatmeal, regular or quick, cooked with water 1 cup 13
Spinach, frozen, cooked 1 cup 11
Milk, whole 1 cup 8
Yogurt, plain, whole 1 cup 8
Lentils, cooked 1 cup 6
Spaghetti sauce, marinara 1 cup 4
Cashew nuts, dry roasted 1 ounce 3

Table source: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/

*Note that the selenium content of foods varies depending on the amount of selenium in the soil and a few other factors such as soil pH levels. So these values are general guidelines, and may vary slightly by geographic location.

Factors that May Affect Your Selenium Intake

As you can see, there’s very little selenium in food. Even so, most people do get adequate selenium from their diet. But adequate selenium, and optimal selenium are two different things!

Plus, there are a few other factors that can affect your intake.

So, before you decide whether you need to supplement, consider the following:

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Where You Live

Selenium is a trace mineral present in soil. So depending where your food was grown, the amount of selenium it contains will vary.

In the U.S., selenium concentrations tend to be low in the Pacific Northwest and Northeast while selenium-rich soil can be found in South Dakota and surrounding areas. But with the transportation of food these days, even people who live in low-selenium areas should be able to get the RDA from their diet.

And it’s true, most Americans consume adequate selenium. According to the most recent National Health and Nutrition Examination Survey, the average selenium intake for Americans two and over is 111 mcg a day.

That said, this falls short of the recommended daily intake for optimal health. So if you live in a low-selenium area, you may want to get your blood levels of selenium checked just in case (we’ll explain how in just a moment).

Your Genetics

Your genes can also affect how much selenium you need. Studies show that there’s a certain genetic inheritance that disrupts your selenoenzyme system.

It’s called a single nucleotide polymorphism (SNP). Basically, this means that a different molecule is switched in for a certain gene pair. This switch affects the production of the key antioxidant selenoenzyme we discussed earlier: glutathione peroxidase (GP).

What happens is a slow version of GP is produced. Now, we saw earlier how GP prevents bone loss by fighting inflammation and neutralizing dangerous free radicals. So, individuals with the slow version of GP are more prone to bone loss and low bone mineral density (BMD).

This genetic twist of fate has also been associated with increased inflammation and risk of osteoarthritis.

All this to say that even if you live in a high selenium area, you may still need to supplement! To find out what your GPs are up to, you can take a blood test (we’ll explain what that looks like below).

Your Dietary Preference

Depending on your diet, you may be at risk of low selenium levels.

This is the case for vegetarians and vegans. Vegetarians typically have far lower blood levels of selenium than omnivores, and it’s even worse for vegans. Selenium levels are an issue for vegans for a couple reasons.

First off, the vegan diet is low in the amino acid methionine. This is of note because our bodies need methionine for optimal use of selenium. And dairy, beef, lamb, turkey, pork, and fish are all high in methionine! The good news is nuts and beans are also high in methionine, so vegans should make sure to eat these foods daily.

The second problem for vegans is that meat, seafood, eggs, and dairy products all contain selenium too! So, by default, the vegan diet rules out a lot of selenium-rich foods. If you’re an omnivore on the other hand, you may very well be getting your 200 mcg of selenium a day.

To find out whether you’re getting adequate selenium, try keeping a food diary for a week. At the end of the week, use the Best Food Sources of Selenium table above to calculate your average daily intake.

But if you want to be sure of your selenium levels, there’s only one thing to do…

Check Your Selenium Levels with a Lab Test

Remember when we talked about glutathione peroxidases or GPs a little earlier? They’re the most important antioxidant enzymes in our body, and they need selenium to activate them.

So, a blood test to check your GP activity is a good indicator of your selenium levels! If your blood test shows low GP activity, then it’s a sign you’re not getting adequate selenium. Or you could have the genetic condition we described above, but in that case, you still need to up your selenium intake.   

The good news is several labs now offer this test! If you’re concerned about your selenium levels, or you simply want to make sure, you can visit one of these labs:  

What to Look for in a Selenium Supplement

If you’re selenium deficient, you may want to consider supplementation in addition to incorporating selenium-rich foods in your diet.

There are a few factors to consider when choosing a supplement. Though selenium is available in multivitamins and as a stand-alone supplement, we’d recommend using high-selenium yeast. To understand why, we need to take a look at the different forms of selenium.

Selenium exists in two forms: inorganic (selenate and selenite) and organic (selenomethionine and selenocysteine). The inorganic form is found in soil, so plants accumulate this form and convert it to it’s organic form.

Most of the selenium in human tissue is in the organic form selenomethionine. A fact that suggests this is the preferred form for humans.

Now, you can find selenium supplements in all these forms: sodium selenite, sodium selenate, selenomethionine, selenocysteine, and high-selenium yeast.

What’s interesting is that research comparing these different forms found that selenomethionine did increase blood and tissue concentrations of selenium more than the other forms. BUT, it wasn’t better at increasing GP activity. Remember, GP is the critical antioxidant enzyme that selenium activates.

So, high-selenium yeast may very well be the better option because it contains a mixture of organic selenium— including both selenomethionine and selenocysteine. And in the same study, researchers found that high-selenium yeast increased GP activity much more than inorganic selenium!

It’s worth noting that high-selenium yeast was also used in a clinical trial that showed reduced cancer incidence and cancer-related deaths¹.

To sum up, your best bet is to choose an organic form of selenium. And incidentally, because AlgaeCal Plus and AlgaeCal Basic are plant-based, they also contain organic selenium in small amounts.

So, your AlgaeCal is a nice compliment to your dietary selenium— along with all the other essential minerals and vitamins your bones crave. This multi-nutrient approach is why AlgaeCal is the only calcium supplement guaranteed to increase your bone density!

Selenium Safety Concerns

There’s a sweet spot with selenium. Either too much or too little isn’t good for you. It’s a “Goldilocks” nutrient that way.

It’s important to note that selenium can be toxic if consumed in excess (a condition called selenosis). By excess, we’re talking more than the No-Observed-Adverse-Effect-Level (NOAEL) of 800 mcg per day. But how can you tell if you’re getting too much selenium?

Well, in the early stages of selenium overload, you might notice a garlic odor in your breath and a metallic taste in your mouth. If you’ve been consuming too much selenium for a while, symptoms to look out for include hair loss, white spots on your nails, brittle nails, and nail loss.

Another concern to note is that if you’re pregnant, excessive selenium intake may cause birth defects.

But keep in mind that consuming more than 800 mcg of selenium a day is hard to accomplish. Selenium exists in minute amounts in most foods, so unless you’re eating brazil nuts by the handful, it’s unlikely you’d ever surpass this limit.

Brazil nuts are the exception because they contain a lot of selenium. The USDA tells us that an average one ounce serving (that’s 6-8 nuts) has around 543.3 mcg of selenium.

So, you shouldn’t eat more than two brazil nuts a day as each nut may contain 140 mcg of selenium. And if you recall, the daily selenium intake recommended for optimal bone health is 200 mcg!

Selenium Takeaways

Selenium is nothing short of essential for human beings.

It plays a critical role in many of the body’s functions from thyroid hormone production to protecting against oxidative stress and inflammation. And these functions happen to be critical for bone health!

In fact, a number of large human studies support selenium’s importance for bone health. The most authoritative of these studies shows a clear relationship between low blood levels of selenium and bone loss.

There are certain factors that might be affecting your selenium levels. Where you live, your diet, and your genes all play a role. If it turns out one or more of these factors is affecting your intake, you have options.

There are several selenium supplements to choose from. Just make sure you pick one that contains the organic form of selenium and delivers no more than 200 mcg per dose— the recommended intake for optimal bone health! As always, it’s a good idea to check with your healthcare professional before taking any new supplements.

And on days when you eat brazil nuts, don’t take additional selenium. Brazil nuts contain more than enough selenium to cover your daily intake. Just two brazil nuts contain around 280 mcg… and could contain more depending on factors like soil and growing season!

So you definitely don’t want to overdo it because too much selenium is toxic. Selenium toxicity, or selenosis, can cause a range of unpleasant side effects like hair loss, brittle nails, and nausea. All this to say, if you do decide to supplement, be mindful of how much selenium you’re consuming.

It’s worth noting that to reap selenium’s beneficial effects on your bones, you also need to consume at least 800 mg of calcium a day. Better yet, for optimal bone health, make sure you’re getting at least 1,200 mg of calcium a day from your diet and supplements.

If you take AlgaeCal Plus, you’ll easily meet this requirement, in addition to getting a little extra selenium (not to mention the 12 other essential minerals for bone health!). But you’ll still need more selenium to meet the optimal daily intake.

So, make sure you review the table above to get an idea of how much selenium you’re consuming. If you don’t think you’re getting enough from diet alone, you may want to consider taking a blood test to find out where you stand!