Selenium: Why we need it and where to find it on a vegan diet

What is selenium?

Selenium(Se) is a trace mineral that is found in the soil. It is essential for the body for a variety of physiological processes but is only needed in small amounts.

In countries like America and Canada, where the soil tends to be rich in selenium, deficiency is rare and reaching the recommended daily allowance (RDA) should be easy to achieve in the diet¹.

In contrast, the UK, Europe (particularly Eastern Europe), and parts of China have fairly low levels of selenium in the soil^1,2.

This disparity between countries means the foods you consume will contain varying amounts depending on where they are grown.

What are the health benefits of selenium?

Selenium has numerous roles within the body and may even be effective in preventing and treating some diseases.

It is one of the main components of selenoproteIns, a unique protein, which helps the body perform daily functions, like DNA production and enzymatic processes³.

These selenoproteins are abundant in the thyroid gland and help with the production and metabolism of thyroid hormones⁴.

Other benefits range from immune health, maintaining good reproductive health, antioxidant properties⁴ to cell and tissue protection⁵.

Studies have found promising results for selenium supplementation in treating autoimmune thyroid disease⁶, and it may be beneficial in other autoimmune diseases, such as HIV.

Selenium supplementation may delay the progression from HIV to aids, and may also prevent secondary illnesses, such as tuberculosis, which have been associated with selenium deficiency^7,8.

Selenium and heart health

Not only does it have benefits for the immune system, but selenium may also prove beneficial in heart health.

Low selenium levels have been associated with cardiomyopathy (disease of the heart muscles).

Maintaining adequate levels of selenium may act as a protective factor for the heart.

This is because selenium is an antioxidant, anti-inflammatory and it may aid the prevention of cell death, and also autophagy (the body’s mechanism to destroy damaged cells)⁹.

Further research suggests that selenium, when added to antioxidant supplements, was associated with a reduced risk of cardiovascular disease and all-cause mortality risk in comparison to consuming standard antioxidant supplements or just selenium supplements on their own¹⁰.

Research into cancer has found that selenium may be protective against different sites, such as prostate, colorectal, breast and lung.

The mechanism behind this is thought to be the antioxidant properties selenium has.

Antioxidants help fight the free radicals, which can lead to cancer. However, at present, the results are mixed and more research is needed¹¹.

Brain health and selenium

Brain health is also an area that has been explored in relation to selenium. One study found significantly lower selenium levels in people with Alzheimer’s Disease compared with healthy controls¹².

Clinical trials are underway to examine whether selenium supplementation can slow down the neurodegenerative effects of Alzheimer’s Disease¹³.

However, researchers have to make sure the benefits to cognitive health outweighs the potential for selenosis, as trials often use higher dosages than the RDA.

Looking for more information on how to eat a healthy vegan diet? Read these next:

• Zinc – why we need it and how to get enough on a vegan diet
• Is a vegan diet healthy? What you need to know
• Top 10 vegan sources of iron: How to maximise your iron absorption

How much selenium do we need?

The RDA for males aged 19 and over is 75 micrograms (μg), and for females aged 19 and over this is  60 micrograms (μg)¹⁴.

There is a gradual increase in requirements across childhood and adolescence, and from 15+ males will have a slightly higher requirement due to their importance in male reproductive health.

RDA of children and adolescents;

• 2-3 years  – 15 micrograms
• 4-6 years  –  20 micrograms
• 7-10 years  – 30 micrograms
• 11-14  years –   45 micrograms
• 15-18  –  70 micrograms for males and 60 micrograms for females¹⁵

For people with autoimmune thyroid disease, supplementation may be beneficial to optimise health¹⁶.

But it’s important to consult with your GP or a registered dietitian first, as supplementation may not be suitable for all.

Which foods are high in selenium?

Brazil nuts are a really good source of selenium, but it is recommended to stick to a couple a day. This is because selenium levels can vary quite a lot in Brazil nuts.

What other vegan sources of selenium are there? The over-arching advice on selenium is to consume a balanced and varied selection of whole foods to achieve your daily requirements.

As a bonus, you’ll also be getting a broad range of other minerals, vitamins and macronutrients too.

Other selenium-rich foods include green and brown lentils, couscous, barley, mushrooms, wholemeal bread, pasta, basmati and brown rice, and cashew nuts¹⁷.

Other foods, that you are likely eating regularly, also have smaller amounts of selenium and will help you reach your RDA.

This includes kidney beans, baked beans, sunflower seeds, chia seeds, pecans, flax seeds and soya milk¹⁷.

What are the signs of selenium deficiency?

There are a number of symptoms that can occur with selenium deficiency.

As selenium plays a role in thyroid health, some symptoms of selenium deficiency are similar to that of an underactive thyroid, such as fatigue and brain fog, hair loss, nail discolouration, a compromised immune system, muscle weakness and male and female infertility issues¹⁸.

Severe cases of selenium deficiency, which is rare, have been associated with more serious side effects, such as cardiomyopathy¹⁹.

Symptoms of selenium deficiency can mirror that of other deficiencies and illnesses, so it’s important to get the relevant tests with your GP to confirm.

Can you have too much selenium?

As with anything, there can always be too much of a good thing. The safe upper limit for selenium is set at 450 micrograms (µg) per day. However, this is not advised, as the RDA is set at a  much lower limit²⁰.

Selenosis is the term used when toxic levels of selenium are present in the body. The symptoms will vary depending on the severity.

Less severe symptoms include; hair loss damaged fingernails,  a garlicy odour to the breath, a metallic taste in the mouth, nausea and vomiting and diarrhoea.

More serious symptoms can include; issues with the nervous system and potential respiratory and heart problems²¹.

Selenosis is rare but can occur in events such as industrial exposure and high dosage supplementation over a prolonged period of time.

Although it can be difficult, due to the varying levels of selenium in the soil, it is possible to get enough selenium on a well-planned vegan diet.

General guidance from the National Institute of Clinical Excellence (NICE) advises against a selenium supplement unless there is evidence of a deficiency ²².

However, if your diet does not include foods containing selenium, a supplement can ensure you reach your daily requirements.

Consult with your GP or a registered dietitian first, to see whether selenium supplementation is suitable for you.

Check the packaging to ensure the supplement does not exceed the RDA.

Maintaining heart health is key to leading a happy, healthy life. 

Thankfully a vegan diet is filled with heart healthy foods! 

References

1. https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/#en5
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4377864/
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7222958/
4. https://pubmed.ncbi.nlm.nih.gov/22381456/
5. https://www.nhs.uk/conditions/vitamins-and-minerals/others/
6. https://pubmed.ncbi.nlm.nih.gov/33894732/
7. https://pubmed.ncbi.nlm.nih.gov/31677697/
8. https://clinicalnutritionespen.com/article/S2405-4577(19)30461-9/fulltext
9. https://www.sciencedirect.com/science/article/pii/S075333222031318
10. https://www.researchgate.net/publication/346787324
11. https://assets.publishing.service.gov.uk/government/
12. https://pubmed.ncbi.nlm.nih.gov/33498452/
13. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6361071/
14. https://assets.publishing.service.gov.uk/government/
15. https://www.bda.uk.com/uploads/assets/
16. https://assets.publishing.service.gov.uk/government/
17. https://www.bda.uk.com/uploads/assets/
18. https://thyroiduk.org/about-selenium/
19. https://onlinelibrary.wiley.com/doi/full/10.1002/ejhf.1644
20. https://assets.publishing.service.gov.uk/government/
21. https://mft.nhs.uk/app/uploads/2020/01/Selenium.pdf
22. https://bnf.nice.org.uk/treatment-summary/selenium-deficiency.html