The trace element selenium and its effects
Selenium is an essential trace element that is extremely important for humans, as it plays a key role in the function and action of various enzymes. It is also an important component of many antioxidants that help to neutralise free radicals in the body.
What are trace elements?
Trace elements are chemical elements that only occur in very low concentrations in the body of living organisms - but they fulfil a very important function, as they are required for various bodily functions. In contrast to macronutrients such as carbohydrates, proteins and fats, which are required in larger quantities, only traces of trace elements are present in the body, but they are nevertheless essential.
Some other examples of trace elements are iron, zinc, copper, manganese, iodine and chromium. These elements are important for numerous bodily processes, including immune function, hormone regulation and metabolism. An inadequate intake of trace elements can lead to various deficiencies and health problems.
Most trace elements are absorbed through food, although some can also be obtained through the environment or supplements. It is important to ensure a balanced diet with an adequate intake of trace elements to prevent deficiencies.
What role does selenium play in the human body?
The trace element fulfils many different functions in the human body. On the one hand, it plays a key role in the function of many enzymes that are required for metabolism and regular cell function. It is able to increase the catalytic activity of certain enzymes and thus accelerate the breakdown of various substances. Some enzymes contain the essential trace element as a structural or activation factor, including glutathione peroxidase, thioredoxin reductase and catalase.
In addition, it is also an important component of many antioxidants that help to neutralise free radicals, which in turn slows down ageing processes and can protect against various diseases triggered by free radicals, such as cardiovascular diseases.
It plays an important role in controlling blood sugar levels by helping with the production of insulin. It also supports the functioning of the cells responsible for absorbing and processing glucose [2].
It is also an important component of healthy thyroid function. This is because it supports the production and breakdown of thyroid hormones and thus contributes to the normal function of the thyroid gland. It is also involved in the synthesis of triiodothyronine (T3) and thyroxine (T4), which are important for metabolic control. It also has antioxidant properties that fight harmful free radicals that can cause damage to thyroid cells.
What role does selenium play specifically for the immune system?
It plays an important role in supporting the immune system due to its involvement in numerous processes. On the one hand, it acts as an antioxidant and protects cells from oxidative stress and harmful free radicals that can be caused by pollution, stress, infections and other factors. Secondly, it regulates inflammation, which is a natural response of the immune system to infection and injury, by controlling the release of inflammatory mediators and cytokines in the body.
It is also involved in the production and activation of immune cells such as T cells, B cells and natural killer cells [3]. It can improve the ability of these cells to recognise and fight infections - thus supporting the immune system's response.
Which foods are particularly high in selenium?
Examples of foods that are high in selenium include fish, seafood, eggs, poultry, nuts, wholemeal products and pulses. A boiled egg contains around 16 µg (micrograms), while a fish fillet (e.g. salmon) contains around 47 µg.
However, of all foods, Brazil nuts in particular are probably one of the best sources of selenium in the diet. However, the selenium content in Brazil nuts can vary. On average, 100 grams of Brazil nuts contain around 1917 µg (micrograms). This corresponds to about 3485% of the recommended daily intake for adults. It is important to note that eating too many Brazil nuts can lead to excessive selenium intake, which can lead to health problems. However, a handful of Brazil nuts (around 30 grams) a day can be a safe and effective source in the diet to avoid a deficiency.
What is the daily requirement of selenium?
The daily requirement depends on various factors such as age, gender or health condition. According to the German Nutrition Society (DGE), the recommended amount for adults is between 60 and 70 µg of selenium per day [4]. However, according to the EFSA (European Food Safety Authority), the Tolerable Upper Intake Level (UL), i.e. the long-term daily intake level at which no negative effects on health are to be expected, is 300 µg/day for adults, pregnant women and breastfeeding mothers. For this reason, many food supplements contain higher doses.
What can be done to improve the body's selenium intake?
In order to optimise the body's selenium intake and avoid a deficiency, you should avoid so-called antinutrients, as some substances, such as phytic acid, can inhibit selenium absorption. Various heavy metals, which are repeatedly detected in small quantities in many foods, can also block selenium absorption.
The best way to guarantee sufficient absorption is to have healthy intestinal flora - because only then will it really be absorbed by the body. A high-fibre diet and probiotic supplements can help to promote healthy intestinal flora.
It is important to note that excessive selenium intake can also have negative effects. It is therefore important not to exceed the recommended daily dose and to speak to a doctor if necessary.
With which vitamins does selenium work together?
The essential trace element works closely with certain vitamins and supports them in their effect in the body: vitamin E and selenium complement each other in their antioxidant effect. Together they protect the cells from oxidative stress and can thus reduce inflammation in the body. Vitamin A and selenium work together to strengthen the immune system and support the health of the skin and eyes. Together with vitamin D, selenium reduces inflammation and strengthens the immune system.
What symptoms can occur with a selenium deficiency?
The symptoms of a deficiency can be varied. A selenium deficiency can manifest itself in tiredness, weakness, concentration problems, memory problems, depression and mood swings, but also in hair loss, muscle cramps and weakness, increased susceptibility to infections, reduced sense of taste, joint pain, brittle nails, infertility and also underweight.
What can cause a selenium deficiency?
The cause of a selenium deficiency could be insufficient intake through the diet, insufficient absorption in the body due to poor functioning of the thyroid gland or other organs or even excessive consumption, e.g. due to taking certain medications. However, chronic illnesses such as liver or kidney disease can also cause a selenium deficiency, as can a disease of the intestine, which generally impairs the absorption of nutrients.
What effects can selenium deficiency have on the psyche?
There is some evidence that the trace element may play a role in the regulation of the psyche and emotional well-being.
A number of studies have shown that selenium deficiency is associated with an increased risk of depressive symptoms and poorer mood states [5]. In particular, selenium may also reduce the risk of developing postnatal depression [6].
However, research on the effects of selenium deficiency is still limited and further studies are needed to understand the exact effects of selenium deficiency on the psyche. It is also important to note that too much selenium can be harmful and it is important not to exceed the recommended daily intake. It is therefore advisable to take dietary supplements only under medical supervision.
When not to take selenium supplements
There are certain situations in which taking them is not recommended or should be avoided: If you are allergic to the trace element, you should not take supplements containing selenium. It also greatly affects thyroid function and can also interact with certain medications, including chemotherapy drugs and blood thinners.
It is important to emphasise that supplements should only be taken under medical supervision to avoid adverse effects. This is because excessive intake can also be toxic and, in the worst case, cause illness.
What effects can excess selenium have?
Excessive selenium intake can lead to so-called selenium poisoning. The symptoms of selenium poisoning can vary from mild to severe and depend on the level of selenium intake. Possible effects include gastrointestinal problems associated with nausea, vomiting, diarrhoea and abdominal pain; hair loss, discolouration and deformation of the nails; neurological symptoms may also occur, including seizures, muscle twitching and paralysis. Excessive selenium intake can also damage the liver and lead to respiratory problems - both of which can even be fatal in the worst cases.
Sources:
[1] https://www.hsph.harvard.edu/nutritionsource/selenium/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5188427/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3169015/
[4] https://www.dge.de/wissenschaft/referenzwerte/selen/? L=0
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986464/
[6] https://pubmed.ncbi.nlm.nih.gov/35058530/
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