Do We Need Vitamin D Tablets?

We need vitamin D above all for healthy bones. It is also said to help against various other diseases. That’s what science says.

What is vitamin D?

When we talk about vitamin D, we don’t mean a specific substance or vitamin. Scientists use the term as a generic term for a group of fat-soluble vitamins – the so-called calciferols. The most important forms include vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

The human body can only produce vitamin D under the influence of light, i.e. UV-B radiation. That is why vitamin D is often referred to in advertising as “the sun hormone”.

Why is vitamin D important for the body?

We need it primarily for our bones. Because thanks to vitamin D, our body can absorb calcium from food. This hardens bones and teeth, for example. It also influences muscle strength and is important for metabolic processes. In adults, deficiency can cause bones to deform, cause pain, and muscles to lose strength.

According to Stiftung Warentest, a deficiency also increases the risk of developing osteoporosis – a weakening of the bones. Deficiency in infants and children puts them at risk of developing rickets , which is a serious disorder of bone growth that can cause permanent skeletal deformity.

What is a vitamin D deficiency?

Strictly speaking, one does not measure vitamin D, but a precursor of the vitamin: 25(OH)D. A value of less than 12 nanograms per milliliter (ng/ml) or less than 30 nanomoles per liter (nmol/l) indicates an inadequate supply with an increased risk of diseases such as rickets, osteoporosis and softening of the bones. A value of 50 nanomoles per liter is optimal .

In a survey by the Robert Koch Institute (RKI), almost 60 percent of adults in Germany remain below this optimal value – but mostly only slightly. The RKI writes that around 15 percent in this country have a value of less than 30 nanomoles per liter. However, there are different measurement methods that lead to different values, which makes it difficult to compare data from different studies or surveys.

No widespread deficiency

It is very controversial whether a large part of the population in Germany suffers from a vitamin D deficiency. The RKI, for example, states: A vitamin D deficiency is present if vitamin D is missing in the body over a longer period of time and if this leads to symptoms.

So if it is measured once that the vitamin D content in the blood is low or even below the recommended values, this does not mean that you actually suffer from a deficiency and should therefore take vitamin D tablets (see “Why does the vitamin D balance fluctuate?”). The Federal Institute for Risk Assessment (BfR) also sees no widespread vitamin D deficiency in Germany , as does the professional association of internists.

Why does the vitamin D balance fluctuate?

Since our vitamin D content in the body depends, among other things, on the season , it can fluctuate. Sometimes it’s low, sometimes it’s higher. The body produces more vitamin D, especially in the warm summer months, because the sun shines frequently and we are exposed to a lot of UV-B radiation.

The Federal Office for Consumer Protection and Food Safety writes that in Germany, an estimated 80 to 90 percent of vitamin D supply comes from endogenous synthesis in the skin – if we are regularly out in the fresh air with enough uncovered skin. In the winter months, however, things look a little different: Our body can only produce vitamin D to a very limited extent.

The UV-B rays required for self-synthesis only reach regions below the 35th degree of latitude all year round. At higher latitudes, the intensity and duration of sufficient radiation decrease and vitamin D production becomes dependent on the season. This also applies to Germany, as it lies between the 47th and 55th degree of latitude.

Body stores vitamin D

The body stores the vitamin D produced in summer in adipose tissue and skeletal muscles, which helps to maintain vitamin D serum concentrations in winter. A study from Sweden showed that low vitamin D levels can occur more frequently in the winter months .  For this purpose, the blood of 540 test persons was examined. In addition, they had to provide regular information about their smoking behavior, physical activity and possible vitamin D supplements.

The result: the average vitamin D level was lower in the winter months than in the summer months. Around 50 percent of the test subjects had a concentration of less than 50 nanomoles per liter for half of the year. In the summer months, the concentration for over 80 percent of the test subjects was over 50 nanomoles per liter, and for 41 percent of these people it was even over 75 nanomoles per liter.

How well does vitamin D protect against serious diseases – and corona?

We already know that vitamin D is particularly important for our bone health. But it is also repeatedly touted as a miracle cure for various diseases. But what exactly is behind these promises is often not scientifically clear. An overview:

Can vitamin D protect against respiratory infections?

In fact, the German Society for Nutrition (DGE) came to the conclusion in a review that a good vitamin D supply can definitely protect against respiratory infections such as a cold. In addition, vitamin D treatment had a positive effect on asthma or COPD sufferers – if they were already suffering from a deficiency. The DGE found an inverse relationship between the vitamin D status and the risk of acute respiratory infections . This means that the lower the vitamin D status, the higher the risk of respiratory infections.

According to the DGE, if the vitamin D supply is insufficient, supplementation (i.e. intake) with vitamin D could have a positive effect on the prevention of acute respiratory infections.

But: With regard to preventive aspects of vitamin D status for asthma, MS and type 1 diabetes mellitus, the available data from observational studies were not clear. The DGE concludes that no data from controlled studies show an association between vitamin D and the prevention of asthma, COPD, MS and type 1 diabetes mellitus.

Is there a link between vitamin D and depression?

We don’t know that yet. According to the DGE, there is evidence of a connection between vitamin D status and depression. However, controlled studies have not yet been able to confirm this. A meta-study from Cambridge University concludes that depression is often associated with a lower vitamin D level .

However, it is unclear whether the low vitamin D is the cause or a side effect . Depression often goes hand in hand with a lack of drive. Affected people go out less often and also do less sport – so they don’t get into the sun as often and cannot replenish their vitamin D balance.

Does Vitamin D Protect Against Cancer and Cardiovascular Disease?

Whether vitamin D can protect us from these diseases is still not proven . In the past, however, numerous studies have dealt with this question. For a study from 2017, over 5,000 healthy participants were given vitamin D and placebos. Result: This had no effect on the risk of cardiovascular diseases.

Another 2018 study also looked at over 5,000 healthy people. They were given high monthly doses of vitamin D for four years. Here, too, the scientists could not find any effect on the prevention of cancer. The DGE writes that there is still a need for research .

Do vitamin D (and other vitamins) help against corona?

Especially on the Internet, many people recommend high-dose vitamin C against a corona infection. In China, patients have been treated with it in experiments, and vitamin C is also used as an additional option in other countries. Studies are currently underway in China. It is currently not possible to estimate whether the majority of Covid-19 patients will ultimately benefit from this, for example because they recover more quickly or die less frequently .

Results so far suggest it could help critically ill patients with pneumonia. There is often a deficiency in the high-risk group. In this respect, it is not clear whether high-dose vitamin C also protects against infection or only corrects an existing deficiency. Similar relationships also exist with vitamin D, which also plays a role in other lung diseases. To what extent a dose can protect against an infection, whether it prevents severe courses or only alleviates the severity of the disease, studies must first prove.

The administration of vitamins or zinc and other minerals, as is customary in some places, should only be a supplementary measure and not a substitute for medical therapy. A preventive effect of the vitamins for non-infected people has not been scientifically proven . Nevertheless, an adequate supply of vitamins and minerals through a healthy diet and a responsible stay in the sun together with exercise lead to a better physical starting point in the face of an infection.

Who Should Take Vitamin D Supplements?

Vitamin D tablets can be advisable for certain people or risk groups such as the elderly over 65 years of age . With increasing age, the skin is often less able to produce vitamin D. According to the recommendation of the Stiftung Warentest, vitamin D preparations are also often useful for chronically ill, immobile and people in need of care.

There is also a recommendation for infants , as they should be protected from direct sunlight in their first year of life. People who cover up their skin for religious or cultural reasons should also consider supplementing with vitamin D tablets.

The consumer center found in a paper that advertising suggests that vitamin D would bring people a health benefit. Influenced by this, many people take vitamin D tablets without even having their blood serum levels checked. Since vitamin D tablets are freely available, many people take them regularly, although very few of them are deficient.

The professional association of German internists advises against taking vitamin D as long as there is no answer to the question of whether the vitamin D level is a consequence or cause of diseases. If you still want to take vitamin D tablets, you should always do so in consultation with a doctor . They can determine the vitamin D content with a blood test. Those with statutory health insurance are reimbursed for this test if there is reasonable suspicion of a deficiency.

Vitamin D can also be overdosed

Vitamin D can accumulate in fat and muscle tissue, which means it can be overdosed. This can cause nausea, vomiting, and abdominal cramps , and in severe cases can also damage the kidneys, disrupt heart rhythms, and lead to unconsciousness or death . Overdosing through natural nutrition and lots of sun exposure alone is not possible – but certain medications, too many vitamin D tablets and foods fortified with vitamin D can.

The BfR recommends a maximum daily amount of 20 micrograms (µg) of vitamin D (= 800 international units iU) in food supplements. Under no circumstances should you consume more than 4000 international units a day.

How much money do manufacturers make with vitamin D tablets?

The dietary supplement business has been booming for years. According to a market research report, sales in pharmacies alone have increased by around 5.8 percent per year over the past five years. In 2019, pharmacies made a total turnover of 2.2 billion euros with food supplements, half of them from the popular minerals and vitamins alone.

In this group, 210 million euros were sold with magnesium preparations. Second place went to vitamins A and D with sales of almost 109 million euros – in pharmacies alone.

Drugstores and companies specializing in dietary supplements are not included in these statistics.