Selenium: levels in plant-based foods vary from region to region A balanced diet provides a sufficient amount of this essential trace element

Selenium is an essential trace element. It must be obtained from food, as the body cannot produce selenium itself. In food, selenium is typically present as a component of amino acids which contain selenium, i. e. mainly as elenomethionine in plant-based foods and as selenocysteine in animal-based foods.

As a component of selenoproteins (proteins containing selenium), selenium has many different functions in the human body. For example, together with other micronutrients, it helps protect human cells from oxidative damage. As a component of enzymes, selenium also regulates cell proliferation (cell reproduction through cell division) and, together with iodine, is essential for normal thyroid function.

The External Link:German Nutrition Society (DGE) estimates that a daily intake of 60 micrograms (μg) of selenium for female persons aged 15 and over and 70 μg for male persons aged 15 and over is appropriate to meet the requirements of this trace element and ensure essential functions of the body. These amounts can be achieved through a balanced diet.

Breastfeeding women pass selenium on to their babies through their milk and therefore have a slightly higher selenium requirement, which, according to the DGE, can be covered by an intake of 75 μg per day.

Although selenium deficiency is very rare in a mixed and varied diet, people who follow a vegan diet are considered a potential risk group for an insufficient intake (see also the following question).

The selenium content in foods mainly depends on the origin of the food. Plants absorb selenium from the soil through their roots. Since the concentration of selenium in soil can vary greatly from region to region, selenium contents in plant-based foods also vary. In animal-based foods, the selenium content depends on the concentration of selenium in animal feed, to which selenium may be added in the European Union. In fish, the selenium content depends on the selenium concentration in the water.

Among plant-based foods, various cruciferous vegetables, such as broccoli and white cabbage, as well as bulb vegetables (garlic, onion), mushrooms, asparagus, pulses (e. g. lentils) and Brazil nuts are considered good sources of selenium. In general, animal-based foods such as eggs, meat and fish are higher in selenium than plant-based foods.

Some plants have a strong ability to accumulate selenium, including certain types of cabbage, bulb vegetables (garlic, onion), pulses (such as lentils) and Brazil nuts (see question: "Which foods are good sources of selenium?"). When following a normal diet, an excess of selenium from food is generally not to be expected in Germany.

It is important to know that, depending on where they are grown, Brazil nuts can sometimes contain such high levels of selenium that excessive selenium intake cannot be ruled out if they are consumed excessively. They should therefore be eaten in moderation.

Finally, selenium may be added to food supplements or other foods for nutritional purposes. As no maximum amounts have been set for this purpose so far, high-dose food supplements, for example, could also contribute to an excessive intake.

The Federal Office for Radiation Protection (BfS) provides information on the consumption of Brazil nuts: External Link:https://www.bfs.de/EN/topics/ion/environment/foodstuffs/brazil-nuts/brazil-nuts_node.html

Selenium is not only an essential nutrient for humans, but also very important for animal health. Since feed crops - just like plant-based foods - naturally contain only small amounts of selenium in Germany and the EU, sufficient supply of selenium for animals cannot be ensured by these sources alone. For this reason, selenium is added to feed, e. g. for cattle or pigs, as a feed additive.

Organic and inorganic selenium compounds are available for this purpose. Organic selenium compounds are generally more readily available in the organism and also accumulate in tissues. In order to ensure consumer safety of animal-based food products, lower maximum levels have been set for the use of organic selenium compounds in feed than for inorganic selenium compounds (see also: Implementing Regulation (EU) 2019/804).

Thanks to the addition of selenium to feed, animal-based food products such as meat and eggs are a more reliable sources of selenium for humans than plant-based foods.

In Europe, animal-based food products are the most reliable sources of selenium. Since the selenium content in plant-based foods depends heavily on the selenium concentration in the soil, vegans who avoid animal products have an increased risk of insufficient selenium intake. For this reason, people who follow a vegan diet should consciously include selenium-rich plant-based foods such as cabbage, bulb vegetables, asparagus and pulses in their diet.

Selenium is an essential nutrient for humans. If too little or no selenium is consumed over a long period of time, or if selenium metabolism is disrupted due to illness, this can have negative consequences for the synthesis of selenoproteins and impair, for example, the immune system, muscle function or sperm production.

Selenium deficiency due to insufficient intake is rare in Germany and Europe and there is currently no scientific evidence that additional selenium intake, for example through food supplements, has a positive effect on the development of chronic diseases in healthy individuals with a balanced diet.

However, there is an increased risk of selenium deficiency in people suffering from diseases associated with reduced uptake or increased loss of selenium, such as chronic inflammatory bowel disease, cystic fibrosis (a congenital metabolic disorder) or renal insufficiency.

Selenium excess is generally not expected in Germany when following a normal diet.

Acute selenium poisoning can occur through the intake of food supplements with extremely high selenium content or if improperly dosed due to misuse. Symptoms may include vomiting, shortness of breath, cardiovascular problems and, in rare cases, even organ failure.

Acute selenium poisoning from ingesting several grams of selenium can lead to ventricular fibrillation and heart failure, resulting in death.

Chronically high selenium intake (e. g. through high dose food supplements) can lead to selenosis or selenium poisoning. This can also cause hair loss, impaired nail formation and garlic-like breath, as well as gastrointestinal complaints (such as nausea and diarrhoea) and neurological problems such as irritability or fatigue.

Hair loss is considered an early and well-established symptom of excessive selenium intake. Based on this endpoint, the European Food Safety Authority (EFSAshort forEuropean Food Safety Authority) revised the tolerable upper intake level (ULshort forTolerable Upper Intake Level) for selenium in 2023. The ULshort forTolerable Upper Intake Level for adults, including pregnant and breastfeeding women, has been reduced from 300 µgshort formicrogram to 255 µgshort formicrogram per day.

Healthy people generally obtain sufficient amounts of selenium from a balanced and varied diet. For this reason, it is not usually necessary to take additional selenium via food supplements.

In order to ensure that consumers have access to a significant amount of selenium through food supplements when needed, while protecting people with adequate supply from excessive intake, the German Federal Institute for Risk Assessment (BfRshort forGerman Federal Institute for Risk Assessment) recommends for food supplements a maximum amount of 40 micrograms (μg) of selenium per daily dose of a product for people over 15 years of age.