Selenium is an important micronutrient in our diet which plays a key role in our metabolism as well as boosting the immune system. Selenium has many other functions in the body and comes in different forms. In this article, I’ll discuss the different forms of selenium and supplements.
Although a selenium deficiency is not very common, low levels of selenium may increase the risk of diseases such as cancer and heart disease according to some studies.
There are a few foods like brazil nuts, sunflower seeds, and animal products which contain selenium, but its also quite unstable and easily destroyed in processing and cooking. And for people with absorption problems, supplementing selenium might be a good idea.
What is Selenium?
Selenium is found in small amounts in all animals and has many functions in keeping the body healthy. It’s an important component of antioxidant enzymes which are created in the body such as glutathione, which protects against free radical damage.
Selenium plays a very important role in keeping our immune system functioning at an optimal level and lowering inflammation in the body.
It also plays an important role in thyroid metabolism and DNA synthesis. And there have been 25 identified selenoprotein genes in humans.
Did you know that Se was named after a Greek term “Selene” In Greek mythology, she was the “goddess of the moon”.
Which form of selenium is better?
Selenium can be found in two different forms: inorganic and organic. Both can be absorbed by the body and used to increase selenium in our body, but studies appear when it comes to organic vs inorganic selenium, organic may be more bioavailable.
There hasn’t been a lot of study in human with regards to comparing the bioavailability and assimilation of selenium from inorganic and organic selenium, but there has been a lot of animal research conducted.
In one study on cows, Se-enriched yeast was found to be much more effective in raising the concentration of selenium in the blood, colostrum, and milk. It also significantly boosted glutathione activity which is important to reduce oxidative stress. 
In another study on sheep, supranutritional supplementation of Se-yeast (organic selenium) was found to be more effective than Na-selenite at raising whole blood concentration in a dose-dependent manner. Whereas there was no difference between increasing doses for the inorganic selenium group. 
These supplements contain the best forms of selenium.
Forms of selenium supplements
- Selenite – Usually found in pet foods and supplements
- Selenate – Normally found in allium and brassica vegetables. Will be found in green superfood powder supplements
- L-Selenomethionine – Found in brazil nuts, cereals, legumes, some selenium and multivitamin supplements
- Se-methyl, L-Selenocysteine – Found in foods like garlic and broccoli, but also sold as a supplemental selenium
- Selenium-enriched yeast – The yeast is grown within a medium which contains inorganic selenium like selenite. It becomes bound and incorporated into yeast proteins and you end up with mostly selenomethionine, which is an organic and highly bioavailable form of selenium
You can normally each of these supplements available in health shops and on places like Amazon.
Research suggests that organic selenium is better, so you should choose either L-Selenomethionine, L-Selenocysteine (also available together), or Selenium-enriched yeast and add to your food or smoothies to boost selenium intake.
Benefits of taking selenium
There are several benefits of selenium which I’ve already talked about, but I will mention a few more just briefly below.
- May improve longevity – Increases levels of intracellular antioxidant enzymes which fight free radical damage and reduces oxidative stress.
- Boosts immune system – Helps prevent infections from infections, including boosting immune function and resistance to HIV
- Reduces the symptoms of asthma – shown to work especially in patients who were low in selenium before given a supplement
- Protects against thyroid dysfunction – regulates the immune system and antibodies which may cause problems with the production of thyroid hormones especially as one gets older
- Protects against cancer – Selenium in high doses (200 micrograms) may be protective against certain types of cancer by reducing DNA damage and helping with DNA repair in the cells
Recommended daily intake for selenium
We don’t need much selenium to remain healthy. The upper tolerable limit has been set at around 400 micrograms per day. However, the daily allowance that you need to prevent a deficiency depends on your age.
- Children who are between 1-3 years old need 20 micrograms per day
- Children who between 4-8 years old need 30 micrograms per day
- Children who are between 9-13 need 40 micrograms per day
- Adults needs around 55 micrograms per day
- Pregnant and breastfeeding women need up to 70 micrograms per day
Main signs of selenium deficiency
Although deficiency of selenium is quite uncommon. But one should be on the lookout for several signs.
- Persistent muscle weakness that isn’t caused by injury or tiredness from activity
- General fatigue which doesn’t go away on its own after rest
- Mental fog and confusion. Feeling like you’re in a daze
- Diffuse hair loss for both men and women
- Poor immune system function and are frequently catching viruses and developing bacterial infections
Who is at risk of developing a deficiency?
Studies have shown that the vast majority of people have enough selenium to avoid frank deficiency and any complications which can arise from it. However, all individuals are different in their ability to absorb and genotype and have different circumstances whereby they may be at a higher risk of developing a selenium deficiency.
Risks factors include the following:
- Being a vegan or vegetarian may decrease your selenium intake if you don’t include certain selenium-rich foods like seeds and brazil nuts in the diet
- Smoking has been identified as a risk factor
- People who have restrictive diets due to the poor economic status
- Where the food is sourced from that you’re eating. For example, one study showed that people in New Zealand had low levels of selenium due to the soil
- Patients with severe burns can have low selenium levels
- Some research suggests that vitamin C may interfere with the uptake of selenium by the tissues
Most people appear to have sufficient levels of selenium from many studies conducted in recent years. However, does that mean they have optimal levels of selenium for disease prevention? I’ll go into more of that later.
Vegan food sources of selenium
Here are a few foods where you can obtain selenium if you’re on a vegetarian or vegan diet.
- Brazil nuts – 1 one cup = 607 mcg
- Sunflower seeds – 1/2 cup = 19 mcg
- Flax seeds – 2 tsp = 4 mcg
- Mushrooms – 1/2 a cup of shiitake mushrooms gives you 18 mcg
- Cabbage – 1 cup = 3.5 mcg
- Spinach – 1 cup = 3 mcg
- Broccoli – 1 cup = 2.5 mcg
Selenium bioavailability: current knowledge and future research requirements https://academic.oup.com/ajcn/article/91/5/1484S/4597437
Toenail selenium concentration and lung cancer in male smokers (Finland).https://www.ncbi.nlm.nih.gov/pubmed/12588088
- Influence of organic versus inorganic dietary selenium supplementation on the concentration of selenium in colostrum, milk, and blood of beef cows https://actavetscand.biomedcentral.com/articles/10.1186/1751-0147-50-43
Organic and inorganic selenium: I. Oral bioavailability in ewes https://academic.oup.com/jas/article-abstract/90/2/568/4764486