Minerals Part V: Fluorine and Selenium

A healthy lifestyle should sensibly include the two minerals fluorine and selenium. Fluorine is well known, we know the substance from a variety of toothpastes. Since fluorine shows a high chemical reactivity, it occurs almost exclusively bound as fluoride. Selenium is much less popular in comparison, but it has outstanding properties and is often unjustly underestimated.

Behind both elements are useful properties that we should make use of every day.

Selenium and fluoride at a glance:

• The German Society for Nutrition recommends 2.9 to 3.8 milligrams as an estimated daily intake of fluoride.
• Fluoride is supplied to the body through fluoridated salt, toothpaste, food and drinking water.
• Fluoride counteracts tooth decay and ensures strong bones in addition to dental health. However, high doses can have a toxic effect on the neuronal development of children.
• An undersupply of fluoride can lead to delayed growth during pregnancy and in the first year of a child’s life.
• The German Nutrition Society recommends a daily selenium intake of 60 to 70 micrograms. Brazil nuts in particular serve as important sources
• An undersupply of selenium can have negative consequences. The lowest threshold value for pathological symptoms is 20 micrograms daily.
• Regular selenium intake exceeding 10 times the recommended value can lead to intoxication with consequences such as hair loss and headaches.
• Selenium is an important building block of various endogenous proteins and is involved in the defence against oxidative stress, the building of DNA and the synthesis of highly active thyroid hormones.

Fluoride belongs to the trace elements: the usual food contains little of it

The German Nutrition Society considers a daily fluoride intake of 2.9 to 3.8 milligrams to be appropriate for adults and adolescents. The exact value is also determined by gender and age. In terms of quantity, fluoride belongs to the trace elements. Since fluoride is present in extremely small amounts in our food, we also get our daily dose in total from fluoridated table salt, toothpaste and drinking water. If you want to take in two milligrams of fluoride through food, you would have to consume, for example, 10 kilograms of vegetables or two kilograms of black tea. If, for example, fluoridated toothpaste and fluoridated salt are not consumed, the daily amount of fluoride is far below the recommendation at about 0.1 to 0.5 milligrams. However, even low daily amounts do not normally cause deficiency symptoms.

Fluoride is controversially discussed: the advantages and disadvantages

For a trace element to be called essential, the substance must have certain properties that are indispensable for our body and at the same time cannot be formed by the body itself. Experts’ opinions on whether fluoride can be dispensed with still differ from time to time. It is proven that fluoride strengthens our teeth and bones. The element undoubtedly supports dental health and can prevent dental damage if used regularly.

However, recent studies show that excessive fluoride intake can have a negative effect on neuronal development, especially that of children. The daily amount of fluoride should therefore always be consumed in consideration of caries prophylaxis and the avoidance of toxic effects on the child’s mental development. Toothpaste should not be overdosed under any circumstances, but used moderately, sensibly and defensively.

Another property again portrays the problematic nature of the trace element fluorine. It has been observed that a lack of fluoride during pregnancy and in the first year of the child’s life can lead to delayed growth. The mechanisms behind this are currently still unknown. In summary, it can be stated that a fluoride overdose can be harmful, but a fluoride deficiency is detrimental with regard to caries prophylaxis and bone strength.

Selenium only in extremely small quantities

Selenium is indisputably one of the essential trace elements. According to the German Nutrition Society, adolescents and adults should take in 60 to 70 micrograms of selenium daily. Various studies have shown that the majority of the population only consumes 40 micrograms daily.

The selenium content in food depends on the soil in which it is cultivated. German cultivated areas are mostly undersupplied; our domestic wheat, for example, contains significantly less selenium than that of North America.

An outstanding source of selenium is the Brazil nut. A single nut can contain up to 100 micrograms. Conversely, this also means that too much of it should not be consumed so that the daily guideline value is not significantly exceeded.

Too much selenium can be toxic

The guideline value given by the German Nutrition Society is only an estimate. To date, only very few clinical pictures are known that can be traced back to an undersupply of selenium. A daily limit of 20 micrograms is considered to be an undersupply with subsequent illnesses. If this value is regularly undershot, various symptoms such as cardiomyopathies can occur. A lowered thyroid hormone level can also indicate a selenium deficiency.

In the context of a selenium overdose, a toxic effect can only occur at very high levels. In this case, 10 times the recommended daily dose would have to be taken over several days. This would result in symptoms of poisoning, which can be very unspecific (for example, headaches or hair loss). Breath containing garlic could indicate intoxication with selenium.

Selenium acts as a radical scavenger, among other things.

It should be mentioned that all the functions of selenium have not yet been clarified. However, selenium is a component of so-called selenoproteins. These include numerous important enzymes. Selenium is thus a component of enzymes that are responsible for the protection against oxidative stress, the building of DNA and the synthesis of the highly active form of the thyroid hormone T3. In addition, it is assumed that selenium itself has an antioxidant effect.

Text sources:

(1) Grandjean, Developmental fluoride neurotoxicity: an updated review, 2019.

(2) Toumba et al, Guidelines on the use of fluoride for caries prevention in children: an updated EAPD policy document, 2019.

(3) Biesalski, Pocket atlas of nutrition, 8th edition, 2020

(4) Rassow et al, Biochemistry, 4th edition, 2016

(5) https://www.dge.de/wissenschaft/referenzwerte/selen/

(6) https://www.dge.de/wissenschaft/referenzwerte/fluorid/

Image sources:

(7) https://www.freepik.com/search?dates=any&format=search&page=1&query=tooth%20paste&sort=popular