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The Healf Source
Selenium Supplements Or Brazil Nuts: Which Is Better?
Written by: Pippa Thackeray
Written on: July 20, 2025
Is your selenium supplement making the grade? Or could we be overlooking the power of the humble Brazil nut?
Selenium is a much talked about nutrient. Its fame built upon tantalising health claims such as its capacity to boost the immune system, the thyroid, and antioxidant defences, as well as its involvement in many other vital functions in the body.
Approximately 18% of the UK population is thought to be deficient in this mineral. But is supplementation always necessary? Could Brazil nuts be a better source of this precious and elusive nutrient?
New research reveals surprising evidence.
Selenium and the body: why do we need this essential nutrient?
Thyroid tissue contains the highest selenium concentration per gram in the body, which is necessary for producing the active thyroid hormone T3 and for selenoproteins that protect thyroid cells from oxidative damage.
A large study found that people with low selenium levels were more likely to develop thyroid issues, including hypothyroidism, thyroid inflammation and swelling. In addition to supporting normal thyroid function, selenium may also help ease symptoms in those already affected.
Selenium is also required for proper immune function and other processes such as cell growth. Better outcomes for conditions such as infections, heart disease and mood disorders have also been observed in patients with higher selenium levels.
Animal studies point toward a link between selenium and breast cancer risk reduction, whilst in human studies, moderate selenium intake is linked to a lower cancer risk relating to the stomach, colon, lung, and other sites.
In terms of reproductive health, selenium is also important for males, as it helps to create sperm. Additionally, fewer complications are seen in pregnant individuals with adequate serum selenium.
Is selenium deficiency a widespread issue?
Selenium is a trace element that plants absorb from the soil.
Around the UK and much of Europe, soil is naturally lower in selenium than other locations globally, largely due to underlying geology and historical glaciation that stripped away mineral-rich topsoil.
In England, Scotland and Wales, on land where acidic igneous rocks are present, the soil is more likely to be lower in selenium. Other factors, such as heavy rainfall, evaporation and pH levels also affect the selenium concentration of soil.
Unlike countries such as Finland, the UK does not routinely enrich fertilisers with selenium, meaning locally grown produce often contains very little.
Are plant-based diets lower in selenium?
Again, the answer lies in the soil.
Unlike livestock, crops show greater variability in selenium content.
And since plant-based diets are more heavily reliant on crops, they are more likely to be lower in selenium.
Is meat high in selenium?
Organ meats are generally higher in selenium because they contain more of the selenium-rich enzyme glutathione peroxidase (GPx), compared to muscle meat.
In liver and kidney organ meats, higher concentrations of trace elements like selenium can accumulate.
That said, in general, animal-derived food products are still relatively low in selenium. In locations where soil is depleted, supplementation of the mineral may be advised for omnivores, as well as those on plant-based diets.
“90% of UK soil is deficient in selenium, however, soil near the sea tends to have a higher level of selenium due to compounds released from seawater. So, if you can buy produce from a farm near the sea, you’re onto a winner! In addition to Brazil nuts, other plant-based sources of selenium include seaweed, kelp in particular.” – Sam Hamrebtan, NT, Founder of The Life Larder
What does the research say about selenium in Brazil nuts?
A recent study has received some media coverage relating to Brazil nuts and their capacity to effectively increase blood selenium levels.
Plant-based dieters and omnivores were randomly assigned to groups. One group consumed 15 g of Brazil nut butter per day, the second received an equivalent 55-microgram dose in supplement form, while another received a placebo.
After two weeks, both the Brazil nut and the supplement groups saw similar increases in selenium.
Looking at this study, several intriguing insights can be drawn.
Authors of the study found that plant-based dieters saw the greatest improvement from both Brazil nut butter and selenium supplements.
The results confirmed that Brazil nuts can be an effective short-term way to raise selenium levels in people on a plant-based diet.
In some ways, selenium supplementation came out as a better option.
Selenoprotein P, as a key biomarker in the study, was about 20% higher with the supplement in both dietary patterns, indicating the possibility of superior bioavailability in supplemental selenium.
Is there still a case for Brazil nuts?
Another study presents opposing evidence suggesting that Brazil nuts possess an edge of higher bioavailability over popular supplement forms like selenomethionine.
Two Brazil nuts a day (averaging 53 micrograms of selenium) increased selenium in subjects by 64.2%, which was comparable to the 61% increase seen with a selenomethionine supplement.
What’s more, the Brazil nut group was likely receiving less selenium than the supplement group due to natural variability. And still this group showed equal or greater biological responses.
Therefore, overall, findings may suggest Brazil nut-derived selenium may offer superior bioavailability.
The study also acknowledges that Brazil nut concentrations of selenium can vary greatly.
In order to reliably boost antioxidant activity and support thyroid function, a selenium supplement from a trusted brand could be what you need to recreate predictable outcomes each time.
Brazil nuts: a closer look
If you’re going to opt for selenium from food sources, Brazil nuts are high on the list of recommendations. Why? They're known to have a high content of monounsaturated and polyunsaturated fats, making them a valuable source of phytochemicals and minerals, such as selenium, magnesium, copper and zinc.
But when it comes to Brazil nuts, what else do we need to consider?
As with the nutrient profiles across many food types, you get a broader spectrum of nutrients than you would from a single-ingredient supplement.
Depending upon personal preference, it may be a more pleasant experience to eat Brazil nut butter, or a small daily dose of Brazil nuts, as it would be to take a capsule or powder.
There is an upper limit established for selenium intake, said to be 255 micrograms per day. An average intake of 1-2 Brazil nuts a day (over a short duration) is the recommended amount recognised by experts in order to avoid excessive consumption.
But, generally speaking, it is notoriously difficult to account for variability in food sources. Brazil nuts harvested from different locations across the globe will contain varying amounts of selenium. Soil acidity, texture, and the overall concentration of selenium influence how much selenium the Brazil nut trees absorb.
Furthermore, Brazil nuts also contain unusually high and variable concentrations of barium and radium, which can pose health risks to humans, primarily through exposure to their radioactive isotopes.
The takeaways
Be it through food or supplement forms, improving your selenium status is linked to many key areas of wellbeing. From supporting antioxidant function and thyroid hormone activity, to improving immune resilience, it's certainly a nutrient not to be overlooked.
As more and more research is released regarding food sources of essential nutrients, it's important to keep your finger on the pulse, whilst recognising that nutrient-dense whole foods should be a focal point of your diet, regardless of what is trending in the headlines.
Shop EAT at Healf for our curated collection of functional foods, travel-ready snacks and nutritional basics for everyday nourishment.
Putting selenium in your supplement stack?
Chronic stress, inflammation or dietary insufficiency can put you at risk for selenium deficiency. Plus, being in a location where the soil is depleted (such as the UK) is yet another reason to prioritise this mighty mineral.
For many people, especially those on a plant-based diet, Brazil nuts offer a tasty and practical way to top up on selenium. But, if consistency, dosage accuracy or therapeutic benefit is the goal for you, then a high-quality selenium supplement may have more to offer.
For support you can rely on, Thorne’s Selenium delivers a highly absorbable selenium form, making it a dependable foundation for daily antioxidant, thyroid and immune support.
Sam Hamrebtan is a Nutritional Therapist and chef with a deep understanding of how healthy soil and quality food can nourish both the body and the planet. Founder of The Life Larder community and former Course Director at the College of Naturopathic Medicine’s Natural Chef School, Sam works to empower people with delicious, nutritious recipes and stories that benefit the environment.
Instagram: @thelifelarder Website & newsletter: www.thelifelarder.co.uk
This article is for informational purposes only, even if and regardless of whether it features the advice of physicians and medical practitioners. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. The views expressed in this article are the views of the expert and do not necessarily represent the views of Healf
Pippa is a content writer and qualified Nutritional Therapist (DipNT) creating research-based content with a passion for many areas of wellbeing, including hormonal health, mental health and digestive health.
As a contributor to The Healf Source, she regularly attends seminars and programmes on a plethora of contemporary health issues and modern research insights with a drive to never stop learning. In addition, interviewing experts and specialists across The Four Pillars: EAT, MOVE, MIND, SLEEP.
In her spare time, she is an avid swimmer, mindfulness and yoga lover, occasionally bringing a raw, honest approach to the topics she faces. You may also discover some personal accounts of eye-opening wellbeing experiences amidst the reality of a disorientating, and often conflicting, modern wellbeing space.
- 1. Selenium and the body: why do we need this essential nutrient?
- 2. Is selenium deficiency a widespread issue?
- 3. Are plant-based diets lower in selenium?
- 4. Is meat high in selenium?
- 5. What does the research say about selenium in Brazil nuts?
- 6. Is there still a case for Brazil nuts?
- 7. Brazil nuts: a closer look
- 8. The takeaways
- 9. Putting selenium in your supplement stack?
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