The Role of Selenium in Cellular Health and Cancer Prevention


Micronutrients are incredibly important and vital to your health, but are you getting enough, and perhaps even more importantly, the right form? Mark Whitacre, Ph.D., is a leading expert on one of the most important micronutrients, selenium.

Story at-a-glance

  • At the cellular level, selenium is an active component of glutathione peroxidase, which has potent antioxidant properties and serves as a first line of defense against build-up of harmful free radicals in your cells
  • By reducing free radicals, selenium also helps reduce your risk of cancer. Studies show higher selenium levels can cut your risk of prostate cancer by as much as 63 percent, and lung and colon cancer by about 50 percent
  • For cancer prevention, the recommended dosage is 200 mcg of SelenoExcell® high selenium yeast per day. Avoid exceeding 400 mcg per day as toxicity may be an issue

Selenium is a trace element a Swedish chemist, Baron Jöns Jacob Berzelius, discovered almost 200 years ago. Today, modern scientists recognize it as an essential mineral for human health, with potent anti-inflammatory, antiviral and anti-cancer activity.

There are fewer than 100 selenium Ph.D. biochemists in the world. Whitacre received his master’s degree in nutrition at Ohio State University in Columbus, Ohio, in the late 1970s — a time when selenium was quickly becoming a hot topic.

“After I finished my master’s degree at Ohio State, I went to Cornell University to get my Ph.D. in nutritional biochemistry and to study under Gerald F. Combs Jr.[,Ph.D., who] was probably the leading authority in selenium research, and probably still is,” Whitacre says.

During his Ph.D. research at Cornell in selenium biochemistry, Whitacre researched the biochemical role of selenium in pancreatic cells. At the time, researchers were just starting to discover the biological necessities for selenium.

Selenium in Health and Disease Prevention

Selenium serves two very important and interrelated roles:

  1. At the cellular level, selenium is an active component of glutathione peroxidase, an enzyme that converts hydrogen peroxide to water. Glutathione peroxidase has potent antioxidant properties, and serves as a first line of defense against build-up of harmful free radicals in your cells.
  2. Selenium also plays an important role in the prevention of cancer. One of the reasons people get cancer is because of excessive free radical production. By reducing free radicals, selenium helps reduce your risk of cancer.

Excessive Iron + Selenium Deficiency = Bad News

Excessive iron can throw a wrench in the works here. By causing a Fenton reaction in the inner mitochondria, iron then reacts with hydrogen peroxide to form hydroxyl free radicals — the most dangerous type of free radicals known.

These excess free radicals can damage mitochondrial DNA, proteins and cell membranes and lead to dysfunction and ultimately premature death of the mitochondria.

This is why I recommend getting your iron level tested once a year, and to maintain a level between 20 and 80 nanograms per milliliter (ng/mL), and ideally between 40 and 60 ng/mL.

While anemia (low iron) can be a serious problem it is easily treated with iron supplementation. The vast majority of people actually have too much iron. The only people who typically do not are premenopausal women and children.

As a result of that excess iron, hydroxyl free radicals are catalyzed, and the situation is further worsened if you’re selenium deficient. A great example of the danger of high iron is thalassemia, a genetic condition that causes intrinsically high levels of iron.

I inherited this from my dad, who also has it. He developed hemochromatosis, (iron overload), which led to bronze diabetes — a specific subset of type 1 diabetes that results when high iron oxidizes your pancreatic islet cells.

Check Your Iron Levels Annually

As noted by Whitacre:

“Excessive iron does create some challenges. Actually, my Ph.D. thesis, looking at the biochemical role of selenium in the pancreatic cell … [showed that] chicks with selenium deficiency get pancreatic fibrosis …

Basically, once [the chicks were] 21 to 28 days [old], when they were selenium deficient on a purified diet, they wouldn’t survive at all … Most of that damage we saw early on — the earliest damage we can detect — was mitochondrial membrane [damage].

We could see the degeneration of that mitochondrial membrane … basically, the peroxide oxidizing and attacking those lipids … [The mitochondrial membrane] is really one of the areas that’s impacted first … because of the generation of free radicals inside the mitochondria.”

It’s important to realize that while selenium deficiency can worsen the situation, selenium will not optimize glutathione peroxidase production to the point of actually protecting you against excessive iron. So, you really need to check your iron levels and donate blood (phlebotomy), should your levels be elevated.

The Selenium-Cancer Connection

Since the 1980s, most of the selenium research has been in the area of cancer prevention. The first study was conducted by Combs, Whitacre’s thesis adviser at Cornell University.

The late Larry C. Clark, Ph.D., and former director of the Arizona Cancer Center’s epidemiology program at the University of Arizona, was another Cornell researcher.

“In 1983, which was my last year at Cornell, [Combs and Clark] started a 10-year study looking at 200 micrograms (mcg) per day of selenium supplementation using high selenium yeast compared to no supplementation …

They found … there was a 50 to 63 percent reduction in cancer rates in colon, lung and prostate, with the highest number of 63 percent rate reduction in prostate cancer …  

That was probably the first study that really looked at the impact of selenium supplementation on cancer reduction. Since that point, there’s been dozens of studies verifying that work,” Whitacre says.

“That work really emphasized … the thought that the glutathione peroxidase reducing free radical production was the biological role. There is some newer work that looks like there may possibly be another function … beyond the antioxidant role of glutathione peroxidase …

Most of the works since [then] has really been looking more at selenium form. That study used SelenoExcell high-selenium yeast, and there’s been several studies that have looked at sodium selenite [and] selenomethionine, and have not seen the same effect …  [F]orm does make a difference.

The SelenoExcell high-selenium yeast has been the most effective form. Matter of fact, selenomethionine had no effect in a very long term cancer research study published in 2011 called the SELECT trial …”

The Form of Selenium You Use Is Very Important

Interestingly, there does not appear to be a significant difference between selenium forms in regard to the amount of glutathione being produced. However, it makes a big difference when you’re looking at cancer incidence. Selenomethionine is a single amino acid where the selenium has replaced the sulfur in methionine. SelenoExcell high selenium yeast is the full protein form, and a more natural food form.

The selenium yeast gives you not just selenomethionine but also methylselenocysteine and selenocysteine. Research suggests methylselenocysteine may be the most active form in reducing cancer, and that’s the form found in high-selenium yeast. It’s not found in selenate, selenite or selenomethionine.

“When you look at the selenium bounty yeast, it does match with the selenium that you see in tuna, for example, or that you see in natural plant forms. It does match more the natural food form, which is in the complete protein form. We don’t know [whether] the protection of the protein makes it more effective, or [if it’s] the form itself that’s in the selenium yeast beyond selenomethionine.

The selenium in selenium yeast has been shown to be about 70 percent selenomethionine. But these other forms that are in the yeast form — and also in Brazil nuts — does have the methylselenocysteine and also selenocysteine that you don’t have in these other selenium forms.

It’s really thought at this stage that the mixture of these forms … like selenomethionine together with methylselenocysteine and selenocysteine, could possibly be the reason why it’s more effective than selenomethionine by itself at … 200 mcg.”

People With Higher Selenium Levels Have Lower Rates of Cancer

When it comes to food, Brazil nuts are an excellent source of selenium, and all you need is two to three per day to meet your daily requirement. Sadly, there have been no comparison studies done to assess the difference between Brazil nuts and selenium from bounty or extracted from yeast. That said:

“There have been studies showing that the lower the blood level of selenium — looking at individuals who consume foods that are higher in selenium compared to individuals who consume foods that are lower in selenium and therefore have very low selenium blood levels — [the] higher the rates of cancer. Those studies do exist,” Whitacre says.

If you use a supplement, you’ll typically find selenium combined with other antioxidants such as vitamin E. According to Whitacre, this is likely because they serve similar antioxidant functions, not because there’s any type of beneficial interactions between them, such as enhancing the absorption. For example, the SELECT trial looked at both vitamin E and selenium on cancer incidence.

That particular trial looked at the alpha form of vitamin E (alpha-tocopherol) and selenomethionine as the selenium source. Neither of these forms had an effect on cancer rates. This does not mean vitamin E and selenium are useless. It simply confirms that the devil’s in the details, so to speak. When it comes to selenium, you really should strive to get it from your whole food in order to reap maximum benefit.

Best Food Sources of Selenium

As a general rule, eating a variety of whole, unprocessed foods will naturally optimize your selenium levels (along with other important nutrients). Good food sources of selenium include:

Brazil nuts (which average about 70 to 90 micrograms per nut) Sardines Wild-caught Alaskan salmon
Pastured organic eggs Sunflower seeds Pasture-raised organic chicken and turkey
Liver (lamb or beef) Chia seeds Mushrooms

In most parts of the U.S., selenium levels in soil tend to be relatively high (northern Nebraska and the Dakotas have soil that is especially high in selenium). However, in other areas such as China, Russia, Australia, New Zealand and Europe, soil levels of selenium tend to be much lower, and if you eat food primarily grown in these areas, a high-quality selenium supplement may be beneficial. Even parts of the U.S. have been identified as selenium-deficient regions, including:

  • The Pacific Northwest
  • Parts of the Great Lakes region and east of it toward New England
  • Parts of the Atlantic Coast

If you live in one of these areas and focus your diet on locally grown foods, you may be low in selenium. You may also have low levels of selenium if you smoke cigarettes, drink alcohol, have had weight loss surgery or have Crohn’s disease or ulcerative colitis.

Dosage and Supplement Recommendations

Selenium is needed in very small, microgram amounts, which is a fraction of a milligram. More is not better here, as toxicity can become an issue. For cancer prevention, the recommended level is 200 mcg per day. Many studies have used as much as 400 mcg per day without ill effect. However, since most of the research supports the use of 200 mcg per day, and shows no significant benefits at higher amounts, I don’t recommend exceeding 200 mcg per day.

If you like Brazil nuts, eating about two to three of them per day will typically be sufficient. If you opt for a supplement, make sure to get the correct form. What you’re looking for is the high-selenium yeast form. SelenoExcell is the scientifically tested and most recommended version.

“There’s been a lot of research looking at other high-selenium yeast forms. The National Cancer Institute [NCI] required high selenium yeast — before it could be used in clinical trials — to be standardized. They … found that some of the high selenium yeast forms in the marketplace were really just taking yeast and supplementing sodium selenite. They were adulterated.

In 1998, the [NCI] signed a clinical trial agreement … with Cypress … that any cancer prevention trial that was going to use high-selenium yeast had to use the standardized form, which is SelenoExcell high-selenium yeast …

The trials that you see since that first trial published in 1996 by Clark and Combs … all the work since then, supported by the NCI, has been the SelenoExcell high-selenium yeast form. Not only does form make a difference — even [among] the high-selenium yeast forms there are some differences. I really want to emphasize that,” Whitacre says.

Selenium Is Important for Optimal Health and Cancer Prevention

The research is quite clear on this point: Making sure you’re getting enough selenium in your diet on a regular basis will help you achieve biological health and reduce your risk of cancer. Considering the fact that heart disease and cancer are both at epidemic levels in the Western world, cutting your risk by eating a few Brazil nuts or taking a high-selenium yeast supplement like SelenoExcell seems like a no-brainer.

As noted by Whitacre, many of the trials show higher blood selenium levels as a result of high selenium yeast supplementation can cut your risk of prostate cancer by as much as 63 percent, and lung and colon cancer by approximately 50 percent. Avoiding toxins and optimizing your vitamin D level, iron level and diet (reducing your net carbs and avoiding processed foods) will provide additional protection.

The Role of Selenium in Cellular Health and Cancer Prevention


Micronutrients are incredibly important and vital to your health, but are you getting enough, and perhaps even more importantly, the right form? Mark Whitacre, Ph.D., is a leading expert on one of the most important micronutrients, selenium.

Story at-a-glance

  • At the cellular level, selenium is an active component of glutathione peroxidase, which has potent antioxidant properties and serves as a first line of defense against build-up of harmful free radicals in your cells
  • By reducing free radicals, selenium also helps reduce your risk of cancer. Studies show higher selenium levels can cut your risk of prostate cancer by as much as 63 percent, and lung and colon cancer by about 50 percent
  • For cancer prevention, the recommended dosage is 200 mcg of SelenoExcell® high selenium yeast per day. Avoid exceeding 400 mcg per day as toxicity may be an issue

Watch the video. URL:https://youtu.be/3ctCH_0t_1M

Selenium is a trace element a Swedish chemist, Baron Jöns Jacob Berzelius, discovered almost 200 years ago. Today, modern scientists recognize it as an essential mineral for human health, with potent anti-inflammatory, antiviral and anti-cancer activity.

There are fewer than 100 selenium Ph.D. biochemists in the world. Whitacre received his master’s degree in nutrition at Ohio State University in Columbus, Ohio, in the late 1970s — a time when selenium was quickly becoming a hot topic.

“After I finished my master’s degree at Ohio State, I went to Cornell University to get my Ph.D. in nutritional biochemistry and to study under Gerald F. Combs Jr.[,Ph.D., who] was probably the leading authority in selenium research, and probably still is,” Whitacre says.

During his Ph.D. research at Cornell in selenium biochemistry, Whitacre researched the biochemical role of selenium in pancreatic cells. At the time, researchers were just starting to discover the biological necessities for selenium.

Selenium in Health and Disease Prevention

Selenium serves two very important and interrelated roles:

  1. At the cellular level, selenium is an active component of glutathione peroxidase, an enzyme that converts hydrogen peroxide to water. Glutathione peroxidase has potent antioxidant properties, and serves as a first line of defense against build-up of harmful free radicals in your cells.
  2. Selenium also plays an important role in the prevention of cancer. One of the reasons people get cancer is because of excessive free radical production. By reducing free radicals, selenium helps reduce your risk of cancer.

Excessive Iron + Selenium Deficiency = Bad News

Excessive iron can throw a wrench in the works here. By causing a Fenton reaction in the inner mitochondria, iron then reacts with hydrogen peroxide to form hydroxyl free radicals — the most dangerous type of free radicals known.

These excess free radicals can damage mitochondrial DNA, proteins and cell membranes and lead to dysfunction and ultimately premature death of the mitochondria.

This is why I recommend getting your iron level tested once a year, and to maintain a level between 20 and 80 nanograms per milliliter (ng/mL), and ideally between 40 and 60 ng/mL.

While anemia (low iron) can be a serious problem it is easily treated with iron supplementation. The vast majority of people actually have too much iron. The only people who typically do not are premenopausal women and children.

As a result of that excess iron, hydroxyl free radicals are catalyzed, and the situation is further worsened if you’re selenium deficient. A great example of the danger of high iron is thalassemia, a genetic condition that causes intrinsically high levels of iron.

I inherited this from my dad, who also has it. He developed hemochromatosis, (iron overload), which led to bronze diabetes — a specific subset of type 1 diabetes that results when high iron oxidizes your pancreatic islet cells.

Check Your Iron Levels Annually

As noted by Whitacre:

“Excessive iron does create some challenges. Actually, my Ph.D. thesis, looking at the biochemical role of selenium in the pancreatic cell … [showed that] chicks with selenium deficiency get pancreatic fibrosis …

Basically, once [the chicks were] 21 to 28 days [old], when they were selenium deficient on a purified diet, they wouldn’t survive at all … Most of that damage we saw early on — the earliest damage we can detect — was mitochondrial membrane [damage].

We could see the degeneration of that mitochondrial membrane … basically, the peroxide oxidizing and attacking those lipids … [The mitochondrial membrane] is really one of the areas that’s impacted first … because of the generation of free radicals inside the mitochondria.”

It’s important to realize that while selenium deficiency can worsen the situation, selenium will not optimize glutathione peroxidase production to the point of actually protecting you against excessive iron. So, you really need to check your iron levels and donate blood (phlebotomy), should your levels be elevated.

The Selenium-Cancer Connection

Since the 1980s, most of the selenium research has been in the area of cancer prevention. The first study was conducted by Combs, Whitacre’s thesis adviser at Cornell University.

The late Larry C. Clark, Ph.D., and former director of the Arizona Cancer Center’s epidemiology program at the University of Arizona, was another Cornell researcher.

“In 1983, which was my last year at Cornell, [Combs and Clark] started a 10-year study looking at 200 micrograms (mcg) per day of selenium supplementation using high selenium yeast compared to no supplementation …

They found … there was a 50 to 63 percent reduction in cancer rates in colon, lung and prostate, with the highest number of 63 percent rate reduction in prostate cancer …  

That was probably the first study that really looked at the impact of selenium supplementation on cancer reduction. Since that point, there’s been dozens of studies verifying that work,” Whitacre says.

“That work really emphasized … the thought that the glutathione peroxidase reducing free radical production was the biological role. There is some newer work that looks like there may possibly be another function … beyond the antioxidant role of glutathione peroxidase …

Most of the works since [then] has really been looking more at selenium form. That study used SelenoExcell high-selenium yeast, and there’s been several studies that have looked at sodium selenite [and] selenomethionine, and have not seen the same effect …  [F]orm does make a difference.

The SelenoExcell high-selenium yeast has been the most effective form. Matter of fact, selenomethionine had no effect in a very long term cancer research study published in 2011 called the SELECT trial …”

The Form of Selenium You Use Is Very Important

Interestingly, there does not appear to be a significant difference between selenium forms in regard to the amount of glutathione being produced. However, it makes a big difference when you’re looking at cancer incidence. Selenomethionine is a single amino acid where the selenium has replaced the sulfur in methionine. SelenoExcell high selenium yeast is the full protein form, and a more natural food form.

The selenium yeast gives you not just selenomethionine but also methylselenocysteine and selenocysteine. Research suggests methylselenocysteine may be the most active form in reducing cancer, and that’s the form found in high-selenium yeast. It’s not found in selenate, selenite or selenomethionine.

“When you look at the selenium bounty yeast, it does match with the selenium that you see in tuna, for example, or that you see in natural plant forms. It does match more the natural food form, which is in the complete protein form. We don’t know [whether] the protection of the protein makes it more effective, or [if it’s] the form itself that’s in the selenium yeast beyond selenomethionine.

The selenium in selenium yeast has been shown to be about 70 percent selenomethionine. But these other forms that are in the yeast form — and also in Brazil nuts — does have the methylselenocysteine and also selenocysteine that you don’t have in these other selenium forms.

It’s really thought at this stage that the mixture of these forms … like selenomethionine together with methylselenocysteine and selenocysteine, could possibly be the reason why it’s more effective than selenomethionine by itself at … 200 mcg.”

People With Higher Selenium Levels Have Lower Rates of Cancer

When it comes to food, Brazil nuts are an excellent source of selenium, and all you need is two to three per day to meet your daily requirement. Sadly, there have been no comparison studies done to assess the difference between Brazil nuts and selenium from bounty or extracted from yeast. That said:

“There have been studies showing that the lower the blood level of selenium — looking at individuals who consume foods that are higher in selenium compared to individuals who consume foods that are lower in selenium and therefore have very low selenium blood levels — [the] higher the rates of cancer. Those studies do exist,” Whitacre says.

If you use a supplement, you’ll typically find selenium combined with other antioxidants such as vitamin E. According to Whitacre, this is likely because they serve similar antioxidant functions, not because there’s any type of beneficial interactions between them, such as enhancing the absorption. For example, the SELECT trial looked at both vitamin E and selenium on cancer incidence.

That particular trial looked at the alpha form of vitamin E (alpha-tocopherol) and selenomethionine as the selenium source. Neither of these forms had an effect on cancer rates. This does not mean vitamin E and selenium are useless. It simply confirms that the devil’s in the details, so to speak. When it comes to selenium, you really should strive to get it from your whole food in order to reap maximum benefit.

Best Food Sources of Selenium

As a general rule, eating a variety of whole, unprocessed foods will naturally optimize your selenium levels (along with other important nutrients). Good food sources of selenium include:

Brazil nuts (which average about 70 to 90 micrograms per nut) Sardines Wild-caught Alaskan salmon
Pastured organic eggs Sunflower seeds Pasture-raised organic chicken and turkey
Liver (lamb or beef) Chia seeds Mushrooms

In most parts of the U.S., selenium levels in soil tend to be relatively high (northern Nebraska and the Dakotas have soil that is especially high in selenium). However, in other areas such as China, Russia, Australia, New Zealand and Europe, soil levels of selenium tend to be much lower, and if you eat food primarily grown in these areas, a high-quality selenium supplement may be beneficial. Even parts of the U.S. have been identified as selenium-deficient regions, including:

  • The Pacific Northwest
  • Parts of the Great Lakes region and east of it toward New England
  • Parts of the Atlantic Coast

If you live in one of these areas and focus your diet on locally grown foods, you may be low in selenium. You may also have low levels of selenium if you smoke cigarettes, drink alcohol, have had weight loss surgery or have Crohn’s disease or ulcerative colitis.

Dosage and Supplement Recommendations

Selenium is needed in very small, microgram amounts, which is a fraction of a milligram. More is not better here, as toxicity can become an issue. For cancer prevention, the recommended level is 200 mcg per day. Many studies have used as much as 400 mcg per day without ill effect. However, since most of the research supports the use of 200 mcg per day, and shows no significant benefits at higher amounts, I don’t recommend exceeding 200 mcg per day.

If you like Brazil nuts, eating about two to three of them per day will typically be sufficient. If you opt for a supplement, make sure to get the correct form. What you’re looking for is the high-selenium yeast form. SelenoExcell is the scientifically tested and most recommended version.

“There’s been a lot of research looking at other high-selenium yeast forms. The National Cancer Institute [NCI] required high selenium yeast — before it could be used in clinical trials — to be standardized. They … found that some of the high selenium yeast forms in the marketplace were really just taking yeast and supplementing sodium selenite. They were adulterated.

In 1998, the [NCI] signed a clinical trial agreement … with Cypress … that any cancer prevention trial that was going to use high-selenium yeast had to use the standardized form, which is SelenoExcell high-selenium yeast …

The trials that you see since that first trial published in 1996 by Clark and Combs … all the work since then, supported by the NCI, has been the SelenoExcell high-selenium yeast form. Not only does form make a difference — even [among] the high-selenium yeast forms there are some differences. I really want to emphasize that,” Whitacre says.

Selenium Is Important for Optimal Health and Cancer Prevention

The research is quite clear on this point: Making sure you’re getting enough selenium in your diet on a regular basis will help you achieve biological health and reduce your risk of cancer. Considering the fact that heart disease and cancer are both at epidemic levels in the Western world, cutting your risk by eating a few Brazil nuts or taking a high-selenium yeast supplement like SelenoExcell seems like a no-brainer.

As noted by Whitacre, many of the trials show higher blood selenium levels as a result of high selenium yeast supplementation can cut your risk of prostate cancer by as much as 63 percent, and lung and colon cancer by approximately 50 percent. Avoiding toxins and optimizing your vitamin D level, iron level and diet (reducing your net carbs and avoiding processed foods) will provide additional protection.

Why Thyroid Health Is Completely Dependent on Selenium


The thyroid is essential to some of the body’s most critical processes, including the development of the nervous and skeletal systems.[1] For the thyroid to function normally, it must receive the right nutrition, and that means getting enough selenium. Selenium is an essential mineral[2] and being deficient can lead to serious health problems such as Keshan disease[3], myxoedematous cretinism[4], Graves’ disease[5], and even thyroid destruction.[6]

Why Thyroid Health Is Completely Dependent on Selenium

Although the body requires selenium, it does not produce selenium and you must get it through your diet. For most people, this isn’t a problem since many common foods are a good source of selenium. Additionally, selenium is available as a nutritional supplement.

Regardless of the source, selenium is a critical nutrient for the body and nowhere is this more evident than the thyroid. In fact, the thyroid has more selenium content per gram than any other organ. It’s also home to certain proteins called selenoproteins[7] which contain selenium-based amino acids.

Before I discuss why this is so important to thyroid health, let’s first understand exactly what the thyroid does.

The 5 Most Common Thyroid Disorders and What You Need To Know

What Is a Thyroid?

Your thyroid is part of your endocrine system and one of the most crucial glands in your body. Located at the base of your throat, the thyroid produces the hormones that play a major role in your body’s growth, maturation, and metabolic processes.[8, 9, 10]

The thyroid hormones produced by the thyroid are triiodothyronine (T3)[11],tetraiodothyronine (T4)[12], and calcitonin.[13]T3 and T4 are critical for a normal metabolism.[14] T4 also supports normal brain function[15], while calcitonin promotes normal bone growth.[16]

How to Support Thyroid Health

There are a few simple steps you can take to support your thyroid. It is imperative that you minimize your stress levels. Stress is actually a hormone response that may negatively impact thyroid function.[17] Exercise is a natural and extremely effective way to combat stress.[18] Exercise can also help stimulate the secretion of thyroid hormones.[19]

Getting enough sleep also helps support a healthy thyroid.[20] Thyroid hormones can directly impact sleep quality.[21]Avoiding toxins like BPA, fluoride, and pesticides is also a smart strategy as they can have a detrimental effect on the thyroid.[22, 23, 24]

Following a balanced diet is one of the easiest ways to support your thyroid. Eat selenium-rich foods, as well as iodine-rich foods, as both are necessary for the synthesis of thyroid hormones.[25] While you’re at it, don’t forget about vitamin A, which also helps support normal thyroid health.[26] When considering your diet, incorporate gluten-free grains since gluten has been associated with autoimmune thyroid diseases.[27]

What Selenium Does for the Thyroid

The importance of selenium for your thyroid cannot be overstated. Most people know that iodine is critical to thyroid health. Selenium is less famous but equally important. Along with iodine and vitamin A, selenium helps remove thyroid-harming substances and supports normal thyroid structure.[7]

Thyroid hormone metabolism is impaired without selenium because iodine-based enzymes, called iodothyronine deiodinases, cannot be synthesized.[28] Iodothyronine deiodinases exist in several forms and are not yet fully understood, but do seem to play a role in preventing hypothyroidism.[29] These enzymes are essential for the activation of thyroid hormones. So, while iodine tends to get most of the credit for thyroid health, it cannot actually carry out its function without help from selenium.

Your body does not produce its own selenium. All selenium must be obtained through food or supplements. Once ingested, the element is broken down into enzymes called selenoproteins.[30] These enzymes exist in many forms, but two of the best understood are glutathione peroxidase (GPx) and thioredoxin reductase (TRx). The GPx and TRxenzymes promote antioxidant abilities on a cellular level.[31] TRx also aids in cell growth and helps process dehydroascorbic acid into vitamin C.[32] None of these vital enzymes could exist without selenium.

Selenium has also been shown to combat several thyroid-debilitating conditions.

The 5 Most Common Thyroid Disorders and What You Need To Know
Also see: The 5 Most Common Thyroid Disorders and What You Need To Know

How the Thyroid Relies on Selenium to Ward Off Disease

Common thyroid maladies can be caused by low selenium intake, including Hashimoto’s thyroiditis.[33] With this condition, the thyroid first becomes inflamed and secretes excessive amounts of hormones. Then, over time, it starts producing far less than it needs.

Conditions like thyroiditis can lead to an imbalance of hormones and that can be the start of major disruptions in the body’s normal processes. Hypothyroidism, which is one such potential consequence, is a condition in which the thyroid fails to provide a sufficient level of thyroid hormones.[34] The outcome can be serious and include abnormal heartbeat[35], low body temperature[36], and nervous system disorders.[37] It can even disrupt the body’s ability to metabolize proteins, carbohydrates, and fats.[38] What can contribute to hypothyroidism? You guessed it, selenium deficiency

Role of Selenium in Nutrition

If thyroid health is important to you, you cannot overlook the importance of selenium. The body is made up of many parts that work together. Each part must be fueled with essential nutrients like selenium. In addition to supporting thyroid health, selenium also plays a role in combating free radicals. To learn more about how selenium supports your body, check out how selenium plays a role in human nutrition.

How Selenium, Vitamin E Increase Prostate Cancer Risk


New data from the much publicized Selenium and Vitamin E Cancer Prevention Trial (SELECT), which sought to determine whether these supplements could protect against the development of prostate cancer, confirm that both antioxidants can be risky business for men.

As previously reported, men receive no preventive benefit from either selenium or vitamin E supplements; in fact, for certain men, these supplements actually increased the risk for prostate cancer.

The new study, published online February 22 in the Journal of the National Cancer Institute, explored which men who take these supplements are most at risk for prostate cancer, and why.

However, the ongoing public health message from the trial remains the same, said a trial investigator.

“Men using these supplements should stop, period. Neither selenium nor vitamin E supplementation confer any known [health] benefits — only risks,” said lead author Alan Kristal, DrPH, from the Fred Hutchinson Cancer Research Center in Seattle, in a press statement.

“Many people think that dietary supplements are helpful or at the least innocuous. This is not true,” he added.

The cohort of 4856 men was culled from SELECT, the larger phase 3 placebo-controlled trial in which more than 35,000 men were randomized to high-dose vitamin E (400 IU/day) and/or selenium (200 µg/day) supplements.

SELECT began in 2001 and was expected to run for 12 years, but it was stopped early, in 2008, after participants had been on the supplements for an average of 5 years. The results demonstrated that there was no protective effect from selenium and suggested that vitamin E increased prostate cancer risk, as reported byMedscape Medical News.

Although the use of the supplements stopped, the study actually continued. After 2 years of follow-up, the men who took vitamin E had a statistically significant 17% increased risk for prostate cancer, as previously reported.

Notably, the rate of prostate cancer detection was higher in the groups that received either supplement alone or a combination of the 2 than in the placebo group (but the difference was significant only in the vitamin E group).

Selenium is a nonmetallic trace element found in plant in foods such as rice, wheat, and Brazil nuts, and in seafood and meat. In a previous large skin cancer prevention trial, it was associated with a reduced risk for prostate cancer. According to the National Cancer Institute, it is an antioxidant that might help control cell damage that can lead to cancer.

Vitamin E is found in a wide range of foods, especially vegetables, vegetable oils, nuts, and egg yolks. Like selenium, vitamin E is considered an antioxidant.

Key: Increased Risk Depends on Baseline Selenium

In this new case–cohort study, 1739 men diagnosed with prostate cancer during SELECT were compared with 3117 men who were not.

Dr. Kristal and colleagues found that baseline selenium status alone, in the absence of supplementation, was not associated with prostate cancer risk.

However, they also found that the effects of the supplements differed substantially between men with low levels at baseline and those with high levels.

Specifically, selenium supplementation increased the risk for prostate cancer in men who already had high selenium levels at baseline.

Before SELECT even began, there was evidence that selenium supplementation would not benefit men who already had an adequate intake of the nutrient.

For this reason, at baseline, the investigators measured the concentration of selenium in the toenails of participants. The plan was to test whether supplementation would benefit only the subset of men with low selenium levels at baseline, they explain.

Instead, they found that men with high selenium levels at baseline who took selenium supplements increased their risk for high-grade cancer by 91% (P = .007). In other words, the levels of selenium in these men became toxic.

The investigators also report that vitamin E increased prostate cancer risk in men, but only in those with low selenium levels at baseline.

Specifically, in the men with low levels of selenium randomized to receive vitamin E alone, the total risk for prostate cancer increased by 63% (P = .02) and the risk for high-grade cancer increased by 111% (P = .01).

This might explain why, in the 2008 SELECT results, only the men randomized to receive vitamin E alone, not those who received both vitamin E and selenium, had an increased risk for prostate cancer.

There is some evidence from basic science to support the idea of a meaningful dynamic. “An interaction between vitamin E and selenium has long been hypothesized because of their activities in preventing lipid peroxidation,” Dr. Kristal and colleagues write.

Selenium, whether from dietary sources or supplements, might protect men from the harmful effects of vitamin E, they suggest. So selenium, at low levels, is not necessarily harmful to men.

Nevertheless, these new results are consistent with the medical literature on supplements and cancer, the investigators report. The message is that nothing good is gained in healthy people.

The literature “suggests that effects of supplementation are dependent upon the nutrient status of the target population, such that supplementation of populations with adequate nutrient status, leading to supraphysiological exposure, has either no effect or increases cancer risk,” they write.

Dietary selenium fails to influence cigarette smoke-induced lung tumorigenesis in A/J mice.


Higher dietary sodium selenite did not inhibit the induction of lung tumors. • Higher dietary selenium increased selenium and GPx protein levels in the lung. • Dietary selenium did not affect lung SOD levels.

Abstract

The goal of the study was to determine if dietary selenium inhibited the induction of lung tumorigenesis by cigarette smoke in A/J mice. Purified diets containing 0.15, 0.5, or 2.0mg/kg selenium in the form of sodium selenite were fed to female A/J mice. Half of the mice in each dietary group were exposed to cigarette smoke 6h/day, 5days/week for five months followed by a four month recovery period in ambient air, while the other half were used as controls. After the recovery period, the mice were euthanized, and their lungs were removed for further analysis. Mice exposed to smoke had a higher tumor incidence and a higher tumor multiplicity, whereas dietary Se did not affect either the tumor incidence or tumor multiplicity. An increase in dietary selenium led to increased levels of selenium in the lung as well as GPx protein levels, but dietary Se did not affect lung SOD protein levels. In conclusion, these data confirm the carcinogenic activity of cigarette smoke in mice but show that dietary Se provided as sodium selenite does not affect smoke-induced carcinogenesis in this model.

Source: cancer letters