Selenium is an essential trace element that the body cannot produce itself. According to the EFSA, it is officially involved in normal thyroid function, normal immune system function, and the protection of cells from oxidative stress. In Germany, average intake is often below recommended levels because the soil in this country is comparatively selenium-poor – yet a clinical deficiency remains rare in healthy adults. This article evaluates what is actually proven by DGE reference values, EFSA claims, and current studies, addresses the much-touted connection to Hashimoto's thyroiditis, and explains at what dosage selenium becomes risky.
TL;DR
According to the EFSA, selenium contributes to normal thyroid function, normal immune system function, and the protection of cells from oxidative stress. The DGE recommends 60 µg per day for women, 70 µg for men, and 75 µg for breastfeeding mothers. A Cochrane review on selenium for Hashimoto's thyroiditis reaches a cautious conclusion: antibody levels decrease measurably in some studies, but the clinical significance of this change is unclear, and no usable data on quality of life exists. According to the EFSA, the safe upper limit is 255 µg per day from all sources combined; the Federal Institute for Risk Assessment (BfR) recommends a maximum daily portion of 45 µg for dietary supplements.
What is selenium and what does the body need it for?
Selenium is a trace element that the body strictly requires in small amounts but cannot form itself. It is incorporated into so-called selenoproteins, which include glutathione peroxidases (important endogenous antioxidants) and enzymes of thyroid metabolism (deiodinases). Through these selenoproteins, selenium is involved in regulating thyroid hormones, protecting cells from oxidative stress, and maintaining normal immune system function. The amount of selenium in plant-based foods depends heavily on the selenium content of the respective soil – and that is lower in large parts of Europe, including Germany, than in North America, for example.
The 6 EFSA-approved functions of selenium at a glance
The European Food Safety Authority (EFSA) has established a list of permitted health claims based on Regulation (EU) No. 432/2012. A total of six claims are approved for selenium. The following table shows them in their exact wording.
| Area | EFSA-approved claim (wording) |
|---|---|
| Thyroid | "Selenium contributes to normal thyroid function" |
| Immune system | "Selenium contributes to the normal function of the immune system" |
| Cell protection | "Selenium contributes to the protection of cells from oxidative stress" |
| Hair | "Selenium contributes to the maintenance of normal hair" |
| Nails | "Selenium contributes to the maintenance of normal nails" |
| Spermatogenesis | "Selenium contributes to normal spermatogenesis" |
These statements are legally permitted, EFSA-verified statements regarding normal function – not claims of healing or statements regarding the treatment or prevention of diseases.
Selenium and the thyroid: What studies really show about Hashimoto's
Hardly any nutrient is as intensely linked to Hashimoto's thyroiditis (an autoimmune disease of the thyroid) online as selenium – but caution is rightly advised here. A systematic Cochrane review that evaluated the available randomized studies on selenium for Hashimoto's thyroiditis reaches a cautious conclusion: in the included studies, selenomethionine supplementation measurably reduced the concentration of thyroid peroxidase antibodies (TPO antibodies). However, the authors of the review explicitly emphasize that the clinical significance of this change remains unclear – a lower lab value is not automatically equivalent to perceptible health benefits. Regarding quality of life, one of the most important patient-relevant endpoints, no usable data were found in any of the included studies. The overall assessment of the review: current evidence is not sufficient to make a confident recommendation for or against selenium supplementation for Hashimoto's thyroiditis; further, methodologically more robust studies are necessary.
For practice, this means: Anyone with a diagnosed thyroid disease such as Hashimoto's thyroiditis should discuss the question of selenium supplementation exclusively with their treating physician instead of dosing themselves with high amounts. Outside of a diagnosed disease, the officially approved EFSA claim "Selenium contributes to normal thyroid function" applies – a statement about normal function when supply is sufficient, not a promise of therapy for an existing condition.
Daily selenium requirement: DGE reference values at a glance
The German Nutrition Society (DGE) provides estimated values for an adequate intake of selenium, which are set at the same level for all age groups starting at 19 years of age.
| Group | Recommended intake |
|---|---|
| Women (19+ years) | 60 µg/day |
| Men (19+ years) | 70 µg/day |
| Pregnant women | 60 µg/day |
| Breastfeeding mothers | 75 µg/day |
These values apply to healthy adults without a diagnosed disease. In the case of existing thyroid or autoimmune diseases, during pregnancy, or when taking medication, individual needs should be clarified by a doctor instead of taking higher doses across the board.
Selenium deficiency in Germany: How big is the risk really?
Because German and many Central European soils are naturally lower in selenium than, for example, North American soils, average selenium intake through diet in Germany is often below the DGE recommendation; studies estimate an average intake in the range of about 30 to 70 µg per day. Nevertheless, most healthy adults do not develop a clinically detectable deficiency as a result – a true selenium deficiency remains rare in healthy people in Germany and Europe. One reason for this: animal products like meat, fish, and eggs are considered more reliable sources of selenium, partly because animal feed in the EU can be enriched with selenium, which partially compensates for the lack of selenium in the soil.
Long-term, severe selenium deficiency can affect immune function, muscle function, and sperm production, among other things. In regions of Asia that are extremely low in selenium, two distinct deficiency diseases are also known: Keshan disease (a heart muscle disease) and Kashin-Beck disease (a joint disease) – both are practically irrelevant in Germany, as no such extreme deficiency occurs here.
How is a selenium deficiency detected?
A selenium deficiency cannot be reliably identified by individual symptoms, as signs such as increased susceptibility to infection or hair loss are non-specific and can have many other causes. A reliable statement is only provided by a blood test that determines the selenium concentration in the serum or plasma. If there is reasonable suspicion – for example, due to a vegan diet, chronic inflammatory bowel diseases, or persistent, unclear complaints – testing via a general practitioner is the most sensible first step before supplementing with high doses on your own.
The best sources of selenium: Foods in comparison
The following overview shows the selenium content of selected foods per 100 grams.
| Food | Selenium content per 100g | Source |
|---|---|---|
| Porcini mushrooms | 187 µg | plant |
| Brazil nuts | 103 µg | plant |
| Tuna (raw) | 82 µg | animal |
| Ocean perch (raw) | 44 µg | animal |
| Mackerel | 39 µg | animal |
An important practical note on Brazil nuts: although they are among the richest selenium foods of all, they also contain small amounts of radioactive substances from the soil, depending on their origin. The Federal Institute for Risk Assessment (BfR) therefore recommends not consuming Brazil nuts in large quantities daily, but only occasionally – two to three kernels already provide a significant portion of the daily requirement. Those who follow a vegan or vegetarian diet should be aware that the selenium content of plant sources fluctuates more strongly than that of animal sources, as it depends directly on the selenium content of the respective soil.
Can you overdose on selenium? Selenosis symptoms and safe upper limit
Yes, it is possible to overdose on selenium – unlike many water-soluble vitamins, excess selenium is not simply excreted. The EFSA has set the total safe upper intake level for adults at 255 µg per day from all sources combined; an older assessment by the Scientific Committee on Food (SCF) from 2000 suggested 300 µg. For dietary supplements, the Federal Institute for Risk Assessment (BfR) recommends, much more cautiously, a maximum daily portion of 45 µg of selenium, in order to maintain a sufficient safety margin from the upper limit when simultaneous intake from a normal diet is considered.
Chronically excessive selenium intake, usually well above 300 to 400 µg per day over a long period, can lead to so-called selenosis. Typical signs include a characteristic garlic-like breath and sweat odor, hair loss, brittle or peeling nails, gastrointestinal complaints, and joint pain. Anyone wishing to supplement selenium should therefore not dose high amounts on their own initiative, but rather stick to the recommended daily portion and, if in doubt, consider the total intake from food and supplements together.
Comparing Selenium Compounds: Sodium Selenite, Selenomethionine, and Selenium Yeast
Dietary supplements use different selenium compounds that differ significantly in their absorption and metabolism—it is worth taking a nuanced look here rather than assuming a blanket "organic is always better." An assessment by the German Federal Institute for Risk Assessment (BfR) classifies the common forms as follows:
- Sodium selenite (inorganic): Is incorporated into selenoproteins via specific, strictly regulated metabolic pathways. This internal bodily regulation counteracts excessive accumulation once the requirement is met. The BfR sees no evidence of an increased health risk with selenite-containing preparations.
- Selenomethionine (organic): Can additionally be incorporated non-specifically and unregulated into normal body proteins that have no selenium function at all. As a result, with continuous intake above normal dietary levels, more selenium can accumulate in the body than with sodium selenite. The BfR considers the chronic tolerability at high dosages to be comparable or even more critical and has so far seen no sufficient basis for classifying selenomethionine as superior to sodium selenite.
- Selenium yeast: According to the BfR, the actual content of organically bound selenium varies greatly depending on the product, from practically 0 to 97 percent of the total selenium content, as uniform purity and identity tests are currently lacking. The BfR therefore recommends caution until standardization is in place.
In practice, this means: The choice of selenium compound is less a question of "better" or "worse," but rather one of adjustability and product quality. More important than the exact compound is that the total dose remains within the recommended range and comes from a source with traceable quality control.
Who benefits from selenium supplementation – and who should be cautious?
For the broad, healthy population in Germany, a balanced diet with regular consumption of fish, meat, and eggs is generally sufficient to cover selenium requirements. Targeted supplementation can be useful for:
- Vegans: without animal sources of selenium and with highly fluctuating selenium levels in plant-based foods, intake may fall below the recommendation.
- People with chronic inflammatory bowel diseases: such as Crohn's disease or ulcerative colitis, as absorption in the intestine can be impaired.
- Dialysis patients: selenium loss via treatment can be increased here, but supplementation should only take place under medical supervision.
- People with diagnosed eating disorders: due to an overall insufficient intake of nutrients.
Independent, high-dose selenium supplementation is not suitable for children under 10 years of age, nor generally for people without a justified additional need. Anyone with a diagnosed thyroid condition, who regularly takes medication, or is pregnant or breastfeeding should consult a doctor or pharmacist before taking selenium supplements.
Sensibly supplementing selenium in everyday life
Unlike some other micronutrients, VEYT currently does not offer an isolated selenium mono-preparation. Those who wish to supplement their selenium intake as part of a more comprehensive daily routine will find selenium combined with zinc and vitamin D3 in the immune system module of the Bloom Woman Complete System, a multi-part nutrient system for different areas of women's health.
Frequently Asked Questions about Selenium
What does selenium do in the body exactly?
Selenium is a component of selenoproteins and, according to the EFSA, contributes, among other things, to normal thyroid function, normal immune system function, protection of cells from oxidative stress, and the maintenance of normal hair and nails.
Does selenium help with Hashimoto's thyroiditis?
A Cochrane review shows that selenium can reduce TPO antibody concentration in studies, but the clinical significance of this change remains unclear, and no usable data is available regarding quality of life. With diagnosed Hashimoto's thyroiditis, supplementation should be coordinated exclusively with a doctor.
How much selenium per day is reasonable?
The German Nutrition Society (DGE) recommends 60 µg for women, 70 µg for men, and 75 µg for breastfeeding women per day. These values apply to healthy adults without diagnosed conditions.
Do I have a high risk of selenium deficiency in Germany?
Average intake in Germany is often below the recommendation, as the soil is lower in selenium than in North America, for example. However, a clinically detectable deficiency remains rare in healthy adults, as animal-based foods represent a comparatively reliable source of selenium.
Can you overdose on selenium?
Yes. The EFSA sets the safe upper limit for adults at 255 µg per day from all sources. Chronically high intake amounts, usually above 300 to 400 µg daily, can lead to selenosis with symptoms such as hair loss, brittle nails, garlic breath, and gastrointestinal complaints.
How much selenium may dietary supplements contain at maximum?
The BfR recommends a maximum daily portion of 45 µg of selenium for dietary supplements so that, in combination with intake through a normal diet, a sufficient safety margin to the upper limit remains.
Are Brazil nuts a good source of selenium?
With approximately 103 µg of selenium per 100 g, Brazil nuts are among the most selenium-rich foods, but depending on their origin, they also contain small amounts of radioactive substances. The BfR therefore recommends eating them only occasionally and not in large daily quantities.
Who should supplement selenium?
Targeted supplementation can be useful for vegans, people with chronic inflammatory bowel diseases, dialysis patients, and in cases of diagnosed eating disorders. In these cases, as well as with thyroid conditions, pregnancy, or breastfeeding, intake should be discussed with a doctor.
Relevant guides at Veyt
- Zinc effects: What studies really show about the immune system, hair, skin, and nails, the other central immune trace element besides selenium.
- Vitamin D3 dosage: How many IU per day really make sense, another central building block for the immune system.
- Biotin effects: What studies really show about hair, skin, and nails, for classifying other beauty micronutrients.
- Multivitamin: Who really benefits and when it is superfluous, for classifying combination products.
- Vitamin B12 deficiency: What studies really show about symptoms, causes, and the right dosage, another common deficiency with an impact on energy and the nervous system.
Sources: German Nutrition Society (DGE) – Selenium Reference Values, Regulation (EU) No. 432/2012 – List of permitted health claims, Cochrane – Selenium supplementation for Hashimoto's thyroiditis, Federal Institute for Risk Assessment (BfR) – Maximum level proposals for selenium, Federal Institute for Risk Assessment (BfR) – Selenium compounds in dietary supplements, Consumer Association – Selenium, a good protection for our body. This article does not replace individual medical advice.
