There is hardly any other medical subject that is discussed as controversially as vitamin D: some see it as a panacea that can even cure cancer, others have long dismissed vitamin D as a hype that has flown away. What is it now?
We reviewed the latest research results, spoke to the experts and analyzed the federal government’s recommendations. Here you will find out, among other things, what tasks vitamin B has at all, how serious a deficiency can actually be and why taking it prophylactically is pointless for most people.
Vitamin D is the umbrella term for a group of fat-soluble vitamins. The most important of these are vitamin D3 and vitamin D2. Strictly speaking, it is actually not a vitamin at all. These are defined as substances that cannot be produced by the body itself and must be ingested through the diet. However, our body itself produces the precursors of the so-called vitamin D.
For this reason, it is the only “vitamin” that is manufactured, more precisely synthesized, in our body. Correct, vitamin D is a so-called prohormone, also known as a hormone precursor. According to the University Hospital Zurich, the D-hormone is also increasingly being talked about.
The majority (80 to 90 percent) of our vitamin D needs – let’s call it that – is produced in the skin. This requires sunlight, more specifically UV-B radiation. Incidentally, the tanning bed is not a good solution for the production of vitamin D, because almost only UV-A radiation reaches the skin there.
If we constantly slathered on sunscreen, we wouldn’t absorb enough vitamin D, reducing vitamin D formation. However, the Federal Food Safety and Veterinary Office (FSVO) says:
We can absorb the remaining percentage through the diet. However, there are not many foods that contain vitamin D in its natural form.
To this end, foodstuffs are increasingly enriched with vitamin D, for example milk substitutes such as oat or soy milk and margarine, but also meat substitutes. In some countries, such as the US, such systematic reinforcements have been shown to contribute to the reduction of vitamin D deficiencies. In Switzerland, too, vitamins D2 and D3 may be added voluntarily to foods, provided that the consumer is informed of this.
Not all people need the same amount of vitamin D. Older people need a little more, especially because older people can metabolize vitamin D less well than young people. The FSVO recommends the following daily amounts of vitamin D – from the sun, diet or supplements:
By way of comparison: a large portion of oily fish (100 grams) – which contains a relatively large amount of vitamin D – contains about 10 to 20 micrograms. Theoretically, this means that on a day without sunlight, such a portion is already enough to cover the daily dose. It’s important to note that these are just estimates, bearing in mind that infants and the elderly have less sun exposure. A maximum of 5 micrograms per daily dose may be added to fortified foods.
Vitamin D has several important jobs. First of all, it plays a decisive role in calcium metabolism: it regulates calcium absorption in the intestine, regulates the calcium level in the blood and thus helps with bone formation.
However, vitamin D receptors are also present in other places in our body, which is why the vitamin has been shown to play a role in other complex metabolic processes. For example, it helps to strengthen muscles, build proteins and regulate hormones. Last but not least, it affects various immune cells and thus contributes to the normal functioning of the immune system.
“Because vitamin D is involved in so many processes in the body, for a long time it was felt that it was a kind of ‘super hormone’,” says metabolism expert Philipp Schütz. This is also one of the reasons why so many people take the vitamin even without a known deficiency – and why an extra intake has so many positive effects. However, according to Schütz, much of this is no longer confirmed today.
“Actually, the same applies to all vitamins: taking them only helps if you have a corresponding deficiency,” says the metabolism expert. If someone has a normal vitamin D level, the additional supplementation usually does not yield much.
In infants and young children, severe vitamin D deficiency can lead to bone growth disorders (rickets). Rickets manifests itself in the form of deformations of the skeleton, because the mineralization (absorption of calcium and phosphate) of the bones is disturbed.
In adulthood, the consequence of a serious deficiency is bone softening (osteomalacia). Even a small deficiency carries the risk of brittle bones (osteoporosis).
According to the BLV, vitamin D deficiency in adults can also lead to the following symptoms: diffuse bone or muscle pain, muscle weakness and general fatigue.
In recent years, observational studies have also found links between vitamin D deficiency and other diseases such as high blood pressure, type 2 diabetes mellitus and cardiovascular disease or cancer. It has not yet been possible to prove whether this relationship is causal, ie whether these diseases are caused by vitamin D deficiency.
According to the BLV if the concentration in the blood serum falls below a certain value in the long term (more precisely below a value of 50 nanomoles per liter of blood serum). As the BLV writes, a distinction is made between undersupply (25-49 nmol/l) and serious deficiency (below 25 nmol/l).
However, such information is more of a guideline, says metabolism expert Philipp Schütz. Exactly when you are clinically deficient is always the subject of discussions about vitamin D – but a “cut-off” has to be defined somewhere. But: “There may also be phases in which you need more than usual,” says Schütz. And further: “If someone is going through an infection, for example, it may well be that this person has a slightly increased need.”
Several cross-sectional studies have shown that certain groups of people have relatively low levels of vitamin D and are therefore more at risk of deficiency, explains Philipp Schütz. These are called risk groups, either because they need more than the rest of the population, or because they tend to get too little vitamin D.
The following persons belong to the risk group:
“A real deficiency does not occur in anyone else – provided that they regularly go out into the fresh air and eat normally,” says Philipp Schütz.
Not even in winter? “As a young, healthy person who goes outside and eats normally, you definitely have a high level in the summer and a lower level in the winter,” says Schütz. But: even if this decreases slightly in winter, it is very unlikely to fall below a certain critical threshold – “so much that it would cause problems”.
In winter, the solar radiation at our latitudes is usually not enough to produce enough vitamin D. Since the vitamin is fat soluble, our body can store it in fat. However, this reminder lasts up to three to four months. So if you sampled in February or March, many of us would tend to have low readings. Still, a routine test without obvious symptoms is not recommended by the FSVO.
“Now you could say: ‘I’ll just go to the doctor and measure my mirror, then I’ll know,'” says EEK chairman Schütz. However, because vitamin D levels are so seasonally dependent, a one-time value is uncertain. And: “Vitamin D testing is very expensive. From a societal point of view, we spend a huge amount of money on the measurement.”
In fact, a survey by the Swiss Medical Council found that about 20 percent of the population had been tested in 2018 – 50 percent more than three years earlier. This percentage increased especially among younger people. According to the authors of the study, this costs CHF 90 million per year.
The FSVO writes: “Regular blood tests can be helpful for people with risk factors. That is for the treating physician to decide.”
The BLV expressly recommends supplementation for all infants, pregnant and breastfeeding women, and for all people over the age of 60 – regardless of the season. In other risk groups, vitamin D preparations are recommended after consultation with the doctor if an undersupply has been established.
Nevertheless, according to Schütz, many people, even people without risk factors, opt for a switch instead of a test to be on the safe side in winter. How does he think? “If you don’t exceed the recommended daily amount, it’s certainly not a bad idea.” So according to the motto: “It’s no use, it can’t hurt.”
In fact, the BLV also writes somewhat vaguely on its website: even in people between the ages of 3 and 60, the body’s own production of vitamin D in winter is not sufficient to meet the need. “Vitamin D supply must therefore be ensured through diet or nutritional preparations.”
As Philipp Schütz explains, these federal recommendations are pragmatic in nature. In particular, when there is an explicit recommendation for supplementation for the over-60s, a prophylactic measure is chosen: “Providing vitamin D preparations costs practically nothing – about 10 centimes per person and day – and actually has zero risk if you takes the recommended dose.”
In this way it can be achieved that the whole of Switzerland – according to studies more than 90 percent – has a vitamin D level in the normal range. Because: just as an excess of vitamin D is not useful for a healthy body, a deficiency can be just as harmful – and ultimately cost a lot. “So it’s a normal prevention strategy with the goal of not having people with vitamin D deficiency,” says Philipp Schütz.
Unlike, for example, vitamin C, which is simply excreted in excessive amounts, vitamin D can lead to overdose. This is because it can be stored in the body due to its fat solubility. However, a lot has to be absorbed to get to this point. This is not possible through the body’s own vitamin D production or natural food, but only through excessive intake of high-dose supplements or medicines.
In Germany, it became known at the end of 2022 that emergency calls for poison had increased sharply in at least one area (Erfurt) due to a vitamin D surplus. Vitamin D rose from 69th place in 2021 to 17th place in the list of drugs most often affected by emergency calls. A single overdose is not yet alarming, a pharmacist tells AWP news agency: “It becomes a problem if you do every day.” If possible, stick to the recommended daily dose of 800 IU (international units).
Metabolism expert Schütz is not surprised by the increase: vitamin D received more attention during and after Corona because of its supposed protection against infection. However, he is not aware of any accumulation in Switzerland.
However, regarding overdoses, the BLV also writes, “To avoid vitamin D overdose, vitamin D from different sources (fortified foods, dietary supplements, medications) should not be consumed at the same time.”
source: watson
I’m Maxine Reitz, a journalist and news writer at 24 Instant News. I specialize in health-related topics and have written hundreds of articles on the subject. My work has been featured in leading publications such as The New York Times, The Guardian, and Healthline. As an experienced professional in the industry, I have consistently demonstrated an ability to develop compelling stories that engage readers.
