Vitamin D (Cholecalciferol)

Vitamin D is a fat-soluble vitamin that our bodies can synthesize themselves under the influence of sunlight. Nevertheless, recent studies indicate that more and more people have too little vitamin D in their blood. However, vitamin D deficiency can have devastating consequences: Since vitamin D is significantly involved in the regulation of calcium balance, a deficiency can lead to instability of the bone skeleton. However, not only a vitamin D deficiency but also an overdose has a negative effect on our body. What is the function of vitamin D in the body and in which foods is its occurrence particularly high? 10 foods with vitamin power

Vitamin D regulates the calcium balance

Vitamin D (cholecalciferol) is a collective term that includes several compounds of fat-soluble vitamins. Of these, vitamin D2, found in plants and fungi, and vitamin D3, found only in animal foods, are particularly important to us humans. In the body, vitamin D is primarily involved in the regulation of calcium and phosphate balance. Vitamin D ensures that calcium from food, or the intestine, can be better absorbed and supports the incorporation of calcium into the bones. It thus plays an important role in bone mineralization. In addition, vitamin D is also involved in regulating the calcium level in the blood: If the calcium level drops, calcitriol can be produced from an inactive vitamin D precursor. Calcitriol then ensures that calcium is released from the bones and that the calcium level in the blood rises again. This ensures that calcium is available for vital metabolic functions such as nerve cell conduction or muscle work.

Vitamin D strengthens the immune system

In addition to regulating calcium balance, vitamin D also plays a significant role in strengthening the immune system. However, exactly how vitamin D contributes to the defense against pathogens has not yet been clarified. It is assumed, however, that vitamin D is instructed by certain cells of the immune system – the T-lymphocytes – to initiate the defense against pathogens. If there is not enough vitamin D in the body, the T-lymphocytes cannot respond to the pathogens and they can settle in the body and multiply without much resistance.

Can vitamin D protect against corona infection?

In the wake of the Corona pandemic, several studies were published linking severe courses of COVID-19 to vitamin D deficiency. Word quickly spread that taking vitamin D supplements could protect against Corona infection. However, experts warn against jumping to conclusions, as the available studies have so far been unable to provide any serious evidence of a causal relationship. Thus, vitamin D deficiency could also be a consequence of COVID-19 or simply a coincidence, since the deficiency is quite common in the population. In addition, scientists point out that vitamin D overdose can have significant health consequences such as organ damage. For at-risk patients who do not get enough exposure to sunlight, it might be advisable to turn to vitamin D supplements after consulting a doctor. However, it is not advisable to take supplements containing vitamin D in high amounts to protect against corona infection without consulting a physician.

Does vitamin D protect against cancer?

However, vitamin D is said to be able not only to strengthen the body’s defenses against typical infectious diseases such as colds, flu or pneumonia, but also to have an anti-cancer effect: Recent studies suggest that with a sufficient vitamin D supply, the risk of certain types of cancer, such as breast cancer or colorectal cancer, could be lower than in people with a vitamin D deficiency. However, vitamin D could not only have a preventive effect, but also have a positive influence on the course of healing in the case of cancer that has already broken out. Vitamin D is thought to have an inhibitory effect on the formation of metastases and tumor growth. This hypothesis has so far been tested in studies for colorectal cancer, prostate cancer, breast cancer, lung cancer and skin cancer. The studies indicate that the chances of survival from one of these cancers are significantly increased by high vitamin D levels.A meta-analysis by the German Cancer Research Center even suggests that ei all cancers, mortality could be reduced by about 13 percent with vitamin D supplementation.

Vitamin D prevents cardiovascular disease

The risk of cardiovascular disease is also thought to be significantly reduced by having enough vitamin D in the blood. For example, one study showed that people over the age of 50 who suffered from a vitamin D deficiency had a significantly increased risk of cardiovascular disease. Further studies are still pending here, however. Similar findings apply to the thesis that an adequate supply of vitamin D can reduce the risk of diseases such as diabetes or multiple sclerosis.

Vitamin D: Occurrence in food

Where is vitamin D found? Vitamin D is found in food, especially in cod liver oil and fish. Particularly rich in the vitamin are fatty fish species such as herring, sardine or salmon. Those who don’t like fish can also turn to dairy products and eggs, as well as various types of mushrooms. Here, especially porcini mushrooms as well as shiitake mushrooms are rich in vitamin D. However, their vitamin D content is far below that of fatty fish.

How much vitamin D a day is advisable?

How much vitamin D should be consumed by the body to protect it from disease is controversial among scientists. Currently, the recommended daily allowance of vitamin D for children and adults is 20 micrograms, according to the German Nutrition Society. Infants under one year of age should consume ten micrograms daily. 20 micrograms of vitamin D is found in the following foods, for example:

  • 80 grams of herring
  • 125 grams salmon
  • 6 to 7 grams cod liver oil
  • 100 grams eel
  • 645 grams porcini mushrooms
  • 600 gram avocado

Some oatmeal and muesli varieties are also enriched with vitamin D and are then also suitable as a vitamin D supplier. With half a cup of oatmeal can then be a content of 55 to 155 units of vitamin D.

Foods provide little vitamin D

In general, it should be noted that the intake of vitamin D through food plays only a minor role. Most of the need for vitamin D is already covered by the production of the body’s own vitamin D. In the case of a deficiency, relevant amounts of vitamin D can best be supplied via dietary supplements. In the case of dietary supplements, vitamin D is usually supplied to the body in the form of drops, capsules or tablets. As a guideline, a daily intake of 20 micrograms or 800 i. E. (international units) is classified as safe.

Sunlight for more vitamin D

Vitamin D can not only be supplied through food, but can also be synthesized by the body itself. Under the influence of sunlight (UV-B light), cholesterol is converted to a precursor of vitamin D. This process represents the significantly more important source of supply compared to intake via food: Up to 90 percent of the vitamin D present in our bodies is synthesized in this way. Since vitamin D is largely produced by the body itself, it does not represent a classic vitamin. This is because, according to the definition, vitamins are only substances that the body cannot produce itself. How much vitamin D is produced when spending time outdoors depends on various factors. These include:

  • Skin pigmentation
  • Age
  • Intensity of sunlight

Vitamin D: content in the blood

A vitamin D content of at least 20 to 30 nanograms of vitamin D per milliliter of blood is considered normal. However, exactly how high the level of vitamin D in the blood should ideally be, is controversial among experts. However, some studies also indicate that vitamin D can only counteract cancer at levels of 32 nanograms per milliliter of blood. Such levels can be achieved either by spending time outdoors regularly or by taking vitamin supplements. The need for vitamin D is increased in babies and small children and during pregnancy and lactation. During this time, special care should be taken to ensure that vitamin D levels do not drop too low. On the next page we inform you about the symptoms and consequences of vitamin D deficiency or overdose.

  • Online information from the German Nutrition Society: vitamin D (calciferols). (Retrieved: 02/2021)

  • Moll, D. / Deutsche ApothekerZeitung (2021): Cancer: possible gain in life years through vitamin D. (Retrieved: 02/2021)

  • Podlogar, J., Smollich, M. (2018): Vitamin D for all? In: Deutsche ApothekerZeitung, Vol. 35, p. 28. (Retrieved: 02/2021).

  • Rößler, A. / Pharmazeutische Zeitung (2021): Lieber raus ins Freie statt Vitamin D schlucken. (Retrieved: 02/2021)

  • Press release of the German Society for Nutrition (2021): Vitamin D and COVID-19. DGE gives overview of the current study situation – no blanket recommendation for vitamin D supplementation possible. Press release 02/2021 of 04.02.2021. (Retrieved: 02/2021).

  • Online information of the Robert Koch Institute (2019): Answers of the Robert Koch Institute to frequently asked questions about vitamin D. (Retrieved: 02/2021)