A New Discovery About Selenium

A New Discovery About Selenium

By now, most of you are familiar with the importance of having adequate selenium in the diet, not just for its current value as an antiviral agent, but also for its other critical functions in the body.

Benefits of Selenium

It has been well established, scientifically, that selenium is essential for supporting the immune system, regulating thyroid hormone metabolism, and for protecting us from the harmful effects of heavy metals, radiation, and chemical toxins (via its ability to help produce glutathione in the body).  Furthermore, due to its anti-inflammatory and antioxidant properties, studies have determined that low selenium (Se) status contributes to ailments characterized by inflammation and oxidative stress, which includes cancer, cardiovascular disease, diabetes, liver disease, metabolic syndrome, and neurodegenerative conditions.

Inadequate serum selenium levels may also increase the risk for the development of “arthropathies”. “Arthropathy is a joint disease, of which arthritis is a type. Arthropathies can be associated with a hematologic (blood) disorder or an infection, such as Lyme disease.”  (Source)  Thus, even those with arthritic conditions need to ensure they are receiving adequate selenium from their diet, and/or supplements.  Of course, every trace mineral, like selenium, in excess becomes a toxic heavy metal. And, selenium overdose “can cause liver and kidney necrosis, neurological disorders and might compromise the reproductive and immune systems”. Therefore, we never want to overdo it when supplementing selenium (nor from eating too many brazil nuts on a consistent basis).

Dietary Selenium

Our best food sources of selenium are cereal grains (if grown in selenium-rich soil), fish, meat, milk, nutritional yeast, and nuts (Brazil nuts containing the highest amount of any food). (Nutritional yeast is not as high as I would have thought, providing only 10% of the Daily Value of selenium in one tablespoon.)  As far as fish and seafood goes, if they contain mercury the bioavailability of the selenium they contain is severely restricted. As well, the amount of fat, protein and heavy metals we ingest will also influence the bioavailability of the selenium we consume.

Okay, now let’s assume we have just consumed some bioavailable selenium. What happens now is that the selenium “is absorbed in the gastrointestinal tract and subsequently transported to the liver, where it is metabolized and used for producing selenoproteins, followed by its distribution to other tissues of the body. Selenoamino acids are actively transported in the duodenum, cecum, and colon through various membrane transport mechanisms”.  This transportation of selenium through the intestines is where things get interesting.

Selenium and Microflora

Earlier studies discovered that diets which included high consumption of selenium-rich nuts, “regulates gut microbiota and promotes the expression of selenoproteins”.

Add to this a mouse study, which found that selenium supplementation “can optimize the gut microbiota for protection against intestinal dysfunction”.

It turns out that dietary selenium affects the gut microbial colonization, “which in turn influences the host’s selenium status and expression of selenoproteins” (selenium bound to amino acids, which facilitates utilization by the body).  None of which is all that surprising to scientists since it has already been determined that  “about 1/4 of all bacteria have genes that encode selenoproteins”.

When selenocompounds from foods are metabolized and incorporated by gut bacteria, these compounds become much more bioavailable to the body. So, the selenium compounds nourish the microflora, but the microflora also make the selenium ultimately more useful to the body. Thus, “selenium deficiency may result in a phenotype of gut microbiota that is more susceptible to cancer, thyroid dysfunctions, inflammatory bowel disease, and cardiovascular disorders”.

Mouse Study

One mouse study looked at how different levels of selenium in the diet (adequate, deficient, or “supranutritional”) affected the mouse microbiome

Providing sufficient or more than sufficient amounts of selenium in the mouse diet did not in fact significantly alter the mice’s intestinal microbiota. However, it did induce significant changes in the composition of the gut microbiota.  Compared to the mice with a selenium-deficient diet, those given more than the basic amount of selenium required for good health, “significantly decreased the abundance of Dorea sp. and increased the levels of microbes with potential protective effects against colitis and intestinal barrier dysfunction, such as Turicibacter and Akkermansi”.

To these researchers there was no doubt that dietary selenium (from food and/or supplementation) affected the composition of the gut microflora and the colonization of the intestinal tract.

Selenium Tug-of-War

While it has been clearly established that there is a symbiotic relationship between us and our microbiome, it appears that there can also be competition when the supply of an essential micronutrient becomes limited.  This was discovered to hold true with selenium (Se): “The Se uptake by intestinal bacteria can negatively influence the expression of selenoproteins in the host, which results in a two to three times lower levels of selenoproteins under Se limiting conditions.”

Which essentially means that, in a tug-of-war over limited supplies of selenium in the body, the microbiome wins. Unfortunately, that win for the gut is a loss for the rest of the body which will remain in a selenium-deficient state, lacking adequate amounts of this critical antioxidant required for immune and detoxification functions.

Here is where the study reveals a new and interesting idea: perhaps taking copious amounts of probiotics (supplements with billions and billions of bacteria), is actually depleting us of selenium as these bacteria are wont to feed on it.

“In view of the high propagated intake of probiotics, the metabolism of Se in these organisms should be investigated in order to assess whether a higher Se intake is recommended.

Irritable Bowel Diseases

It has been noted that selenium deficiency and “inadequate selenoprotein expression impair innate and adaptive immune responses, especially at the colonic level where an increase in inflammatory cytokines is observed. In addition, low intake of Se might result in a phenotype of the gut microbiota that is more susceptible to colitis and infection by Salmonella typhimurium”.

Which means, in turn, that a diet with a good amount of selenium can improve the gut microflora to the point where it can protect against intestinal dysfunctions.  This concept is further proven by the fact that around 31% of people with IBD are found to be deficient in selenium. (It is believed that adequate selenium improves symptoms of IBD due to the ability of selenoproteins to reduce inflammatory responses in the body.)

Other Gut-Related Benefits

Aside from its benefits to IBD, the enhancement of microflora by selenium is also linked to improving thyroid function. It is even possible that the thyroid gland’s requirement for selenium may ultimately be due to its positive effect upon the microbiome.  Now let’s see what this study had to say about cardiovascular disease (CV) since an imbalance in microflora has already been identified as a contributing factor for the development of CV: “Despite multiple human clinical studies revealing associations between gut microbiota composition with the development of cardiovascular diseases, few studies have provided mechanistic or causal evidence of a direct role of Se in gut microbiota in this context.

One other ailment addressed in this study was Alzheimer’s disease (AD). Here, the researchers pointed to another study in which “long-term dietary supplementation (3 months) with Se enriched yeast in triple transgenic mouse model of Alzheimer disease significantly improved spatial learning, retention of neuronal memory and activity”.

This study is backed up by another, done on humans, where patients with AD were given a probiotic formula (Lactobacillus acidophilus, Bifidobacterium bifidum and Bifidobacterium longum), along with a selenium supplement (200 mcg/day). This “resulted in improved cognitive function and enhanced metabolic profile”.  (Study: Selenium in Human Health and Gut Microflora)

The Best Selenium Supplement

My research over the past few years has led me to conclude that yeast-derived selenium is the best form of selenium to supplement with (something Dr. Mercola also believes).

There are a variety of forms of selenium to supplement with, the worst being sodium selenite (essentially gypsum), an inorganic form found in cheap supplements. Currently the two most common forms found in supplements are yeast-derived and selenomethionine (SeMet).

In a study comparing selenomethionine with selenium-enriched yeast the winner was clear: “Results from clinical trials suggest that selenium-enriched yeast (SY) but not selenomethionine (SeMet) may be effective at reducing prostate cancer risk. Overall, we showed for the first time, reductions in biomarkers of oxidative stress following supplementation with SY but not SeMet in healthy men.”   (Study)

Fortunately for consumers of NutriStart products, we came to this conclusion on the superiority of yeast-derived selenium many years ago. Thus our NutriPods  (100 mcg per packet), and Mineral Mix (100 mcg per 2 caps) products have always used the trademarked SelenoExcell form of selenium.


As consumer awareness of the importance of a healthy microbiome grows, it is also important that this requirement of the gut for selenium does not get overlooked in the rush to purchase more probiotics. As with the idea that prebiotics may be more important than probiotics, so too we must remember to provide our microbiome with adequate selenium. Rather than just dumping huge amounts of probiotic bacteria into the gut, we need to ensure that our resident colonies are getting the food that they require to thrive, and selenium is clearly one of the most important foods for our friendly flora.

Sign Up For Our Newsletter

* indicates required
  • Contact

  • NutriStart Vitamin Company

  • 14-755 Vanalman Avenue

  • Victoria, BC

  • 1-800-813-4233

Scroll to Top