Selenium: Benefits, dosage, and the best sources
ca. 11 Minuten
Selenium is one of the trace elements that many people know little about, even though the body needs it every day. There are surprisingly many misconceptions surrounding this mineral: some people take high-dose supplements without a second thought, while others wonder whether their diet provides enough. As is often the case, the truth lies somewhere in the middle. This article explains how selenium works in the body, how much you really need, which foods provide a reliable supply, and when supplementation is useful—and when it is not.
Table of contents
- Key takeaways
- Selenium in the body: How the trace element really works
- How much selenium per day? Reference values and limits
- Selenium-rich foods: Animal-based, plant-based, and regional
- Using selenium wisely: Diet and supplementation
- My take on selenium in everyday life
- Optimize your selenium intake with mybody x
- FAQ
Key takeaways
| Point | Details |
|---|---|
| Selenium is not a cure-all | It works as a building block of selenoproteins, not as a general health booster. |
| Dosage determines benefit or harm | Too little is harmful, but so is too much: the range between the required amount and an overdose is narrow. |
| Animal sources provide the most reliable supply | Fish, meat, and eggs provide readily available selenium, regardless of the soil. |
| Brazil nuts are not an everyday snack | As few as two or three nuts can exceed the daily requirement. |
| Supplements only when truly needed | In most cases, people who eat a balanced diet do not need an additional supplement. |
Selenium in the body: How the trace element really works
Selenium is neither a vitamin nor a mineral in the traditional sense. It is a trace element that the body cannot produce itself, so it must be regularly obtained through food. What makes it so special is that selenium is incorporated directly into proteins as an amino acid called selenocysteine. This incorporation occurs through a unique, genetically encoded mechanism not found with any other amino acid.
The result is what are known as selenoproteins. The body produces at least 25 of these proteins, which have antioxidant and thyroid-regulating functions. The best-known include glutathione peroxidases, which protect cells from oxidative stress, as well as thioredoxin reductases and iodothyronine deiodinases. The latter are essential for converting thyroid hormones.
Anyone who wants to learn more about the connection between selenium and the thyroid can find a more detailed overview there. This connection is often underestimated: a poorly nourished thyroid can function like an engine without oil, even when iodine levels are normal.
The benefits of selenium stem mainly from its availability for incorporation into functional selenoproteins, not from a simple antioxidant effect. This is an important distinction. Selenium is not a miracle supplement that you can simply take in high doses to get more benefits. Beyond a certain level, all selenoproteins are saturated. Taking more then no longer helps and may cause harm.
Pro tip: Serum selenium levels alone do not always show whether you have optimal levels. Functional markers such as selenoprotein P are considered more informative in research because they directly reflect tissue levels.
The link between selenium and the immune system is also well established. Selenoproteins regulate inflammatory responses and support immune cell activity. This makes the trace element a relevant factor in fighting infections, but that should not be taken as a free pass to use high doses.
How much selenium per day? Reference values and limits
This is where things get specific, and where most people make mistakes. The question “How much selenium per day?” has a clear answer, but it has two sides: a target value and an upper limit.
The D-A-CH reference values recommend the following daily selenium amounts for healthy adults:
- Men: 70 micrograms per day
- Women: 60 micrograms per day
- Breastfeeding mothers: 75 micrograms per day
These reference values are considered target values for healthy people and reflect the average requirement. They are not a minimum that you absolutely have to meet exactly every day, but they do provide a useful guideline.
The other side is the safety limit. The EFSA sets the maximum total intake for adults at 255 micrograms per day, including all sources from food and supplements. This limit also applies during pregnancy and breastfeeding.
What happens if you consistently take in too much? The answer is unpleasant. A chronically high selenium intake can cause symptoms such as hair loss, brittle nails, garlic-like breath, and neurological problems. This condition is called selenosis and is almost always caused by uncontrolled supplementation, not diet alone.
Important: The gap between the recommended daily intake (60 to 70 µg) and the safe upper limit (255 µg) sounds large. But if you take a 200 µg supplement and also eat selenium-rich foods, you can exceed this limit faster than you might think.
Selenium deficiency is relatively rare in Europe. It occurs more frequently with a vegan diet, certain illnesses, or malabsorption. Typical symptoms of selenium deficiency include fatigue, muscle weakness, a weakened immune system, and, in the worst cases, heart problems. If you notice these symptoms, you should consult a doctor first before starting supplements on your own.
Pro tip: Before buying a selenium supplement, add up the amount from your diet and the planned supplement. High-dose supplements containing 200 µg should only be taken after consulting a doctor or nutrition professional.
Selenium-rich foods: Animal-based, plant-based, and regional
Selenium levels in foods are anything but uniform. The selenium content of a food depends greatly on how much selenium was present in the soil where a plant grew or an animal lived. Central Europe is among the regions with relatively selenium-poor soils, making plant sources less reliable than animal sources.
Comparison: Selenium content in common foods
| Food | Selenium content (approx.) | Special feature |
|---|---|---|
| Brazil nuts (2 pieces) | 100 to 200 µg | Highly variable; overdose is possible |
| Haddock (100 g) | 30 to 50 µg | Reliable, readily available source |
| Tuna (100 g) | 80 to 100 µg | High content, but be mindful of heavy metal contamination |
| Chicken egg (1 piece) | 10 to 15 µg | Good everyday source, easy to combine |
| Beef (100 g) | 10 to 30 µg | Varies depending on feed |
| Lentils (100 g, cooked) | 2 to 5 µg | Highly dependent on soil |
Selenium in haddock is one of the most reliable sources of all. Marine fish absorb selenium directly from seawater, regardless of the soil. This makes them a dependable option, especially for people who eat little red meat. Those who regularly eat fish are generally well supplied.
Brazil nuts are a special case. They’re considered one of the richest natural sources of selenium in the world, but the selenium content varies enormously. Just two or three nuts can exceed the daily requirement. That makes them unsuitable as a daily snack. Two to three nuts per week is a more reasonable amount.
Anyone who wants to learn more about selenium-rich foods can find a detailed overview of the best sources for 2025 there.
For people who eat a plant-based diet, it’s worth checking where their food comes from. Grain from North America or Canada often contains significantly more selenium than European grain because the soil there is richer in selenium. Mineral content in plant-based foods also varies considerably depending on where and how they are grown.
- Animal-based sources: reliable, highly bioavailable, and less dependent on soil
- Fish and seafood: especially recommended; selenium in haddock and tuna is readily available
- Brazil nuts: high selenium content, but be careful about frequency and quantity
- Plant-based sources: highly variable; monitor intake closely on a vegan diet
Using selenium wisely: Diet and supplementation
When does a selenium supplement make sense? And what should you look for when buying one? Many people who want to improve their intake ask themselves these questions.
First, the honest answer: If you eat a varied diet, regularly eat fish, meat, or eggs, and have no underlying condition, you usually don’t need a supplement. Your diet provides enough. The following groups are different:
- People with a vegan or strongly plant-based diet
- People with gastrointestinal conditions that impair absorption
- People who have had certain surgeries or have malabsorption problems
- People with a deficiency confirmed by laboratory tests
If you want to buy selenium supplements, there are two main forms: selenomethionine (organic) and sodium selenite (inorganic). Selenomethionine is often more bioavailable than inorganic sodium selenite, but dosage and individual nutritional status are more important than the choice of form alone.
What to keep in mind when taking it:
- Never combine multiple supplements without checking the total amount
- Multivitamins often already contain selenium. Add this amount to your supplement
- Long-term high selenium intake can cause neurological symptoms and changes to organs
- Vitamin C can slightly affect the absorption of inorganic selenium; vitamin E works synergistically to protect cells
Nutrient deficiencies are easiest to spot when you watch for warning signs. If you’d like to learn more about recognizing nutrient deficiencies, you’ll find practical information there about various trace elements.
Pro tip: Think of nutrition as the foundation and supplements as a way to fill specific gaps. Taking supplements without lab results means you’re in the dark and risk doing more harm than good.
My take on selenium in everyday life
At mybody x, I regularly see how people approach selenium. And honestly, I’m always surprised by how often the pendulum swings in the wrong direction. Not toward deficiency, but toward overdose.
Many people turn to high-dose supplements containing 200 µg because they’ve read somewhere that selenium is good for the immune system. That’s generally true, but more is definitely not better here. The health benefits of selenium don’t come from taking the maximum amount, but from ensuring the selenoproteins have an adequate supply. Exceeding this threshold risks selenosis, which is no small matter.
What I’ve learned: Selenium deficiency is actually rare in Europe. People who regularly eat fish or meat are usually well covered. The real at-risk groups are people following a vegan diet or with malabsorption, not healthy people looking to optimize their bodies.
My advice: Get your selenium levels tested before taking supplements. And if you do take supplements, choose a dose that meets your actual needs—not one that sounds like it will help more.
— MYBODY X
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FAQ
What are typical symptoms of selenium deficiency?
Typical symptoms of selenium deficiency include persistent fatigue, muscle weakness, a weakened immune system, and thyroid problems. In severe cases, a deficiency can lead to heart problems, although this is rare in Europe.
How much selenium is recommended daily?
The D-A-CH reference values recommend 70 µg per day for men and 60 µg for women. The EFSA safe upper limit is 255 µg per day from all sources combined.
Which foods are particularly rich in selenium?
Foods rich in selenium include seafood such as haddock and tuna, meat, eggs, and Brazil nuts. Plant-based sources such as legumes and grains vary considerably depending on where they come from.
Is selenium good for the immune system?
Yes, selenium and the immune system are directly connected. Selenoproteins regulate inflammatory responses and support immune cells. Getting enough is important, but taking too much offers no additional benefits.
When should I buy selenium supplements?
Selenium supplements are useful in cases of a confirmed deficiency, a vegan diet, or malabsorption. People who eat a varied diet that includes animal products generally don't need a supplement.
