Vitamin D is one of the few vitamins that we know quite clearly that most of us have low levels of. The reason for the widespread deficit is also clear (I almost wrote clear as day): we don’t get enough sun.

What this means for our health has become increasingly clear in recent years. The findings are not only fascinating, but also of practical relevance. As if that weren’t enough, the solution is extremely simple, largely safe and can demonstrably help prevent illness. Let’s look at all of this in turn.

A good 60 percent of us have a vitamin D blood level that represents a deficit even by conservative standards, which specifically means that the value is below 50 nanomoles per liter (more on the values ​​and units in a moment).

In short, vitamin D blood levels in our country, as in many neighboring countries, are on average low, sometimes shockingly low, because many of us don’t spend enough time outdoors. Vitamin D is hardly found in food, the very few exceptions include fatty fish, such as salmon, and sun-dried mushrooms, especially shiitake mushrooms. Although avocado is very healthy, contrary to a popular internet myth, it does not contain vitamin D.

When the body can produce vitamin D

Vitamin D is actually not a vitamin in the strict sense because our body can produce it itself – but we need the sun for that. But it is precisely at this point that there are a lot of misunderstandings.

In Germany and Europe in general, we live quite far from the equator, which means that the sun only rises so high in the sky in and around the summer months that enough radiation reaches our skin to stimulate it to produce vitamin D.

In fact, our skin only produces vitamin D between March and October, and roughly speaking only between 10 a.m. and 3 p.m. (and of course only when our body is not completely covered by clothes, as usual).

Rule of thumb: pay attention to the position of the sun

There is a rule of thumb that can be used to estimate whether the sun is high enough in the sky for vitamin D production: If the shadow your body casts on the ground is longer than you are, then the sun is too low in the sky and your skin is not producing vitamin D.

Only when the shadow of your body on the ground becomes shorter than your body does the body produce vitamin D. There is one Free appwith which you can check in real time how much vitamin D production you can expect in the place where you are currently staying. The app is called “dminder” (based on the English “reminder”) and was co-developed by a prominent vitamin D researcher. (…)

From bone mineralization to cancer protection

Why do we even need vitamin D? The “classic” function of vitamin D, which was discovered decades ago, is to transport the calcium that we consume through drinking water or food – for example in the form of yogurt, kale or legumes – and which strengthens our bones, from the small intestine into the bloodstream.

Without vitamin D, no matter how much calcium we eat, there simply isn’t enough reaching the bones to “mineralize” them, i.e. build them up. What can then develop in extreme cases is a disease called “rickets”. (…)

Vitamin D doesn’t just strengthen bones

However, recent findings suggest that vitamin D is not only important for bone health, but also plays a role in numerous processes in the body – and this may require higher vitamin D blood levels and correspondingly higher supplement doses.

A large study that recently appeared in the New England Journal of Medicine is particularly interesting. In this study, a team of Harvard researchers divided more than 25,000 test subjects into two groups.

Some received 2,000 units of vitamin D3 supplementation every day for a good five years, while others received a placebo (vitamin D is available as a supplement in two forms, D2 and D3; D3 is generally considered the preferred, more effective variant). The participants in the experiment were on average 67 years old.

What the units are all about

It is noteworthy that the test subjects had picture-perfect vitamin D blood levels at the start of the experiment, before supplementation was given: their values ​​were on average 77 nanomoles per liter and thus far above the German average – from the Robert Koch study mentioned at the beginning – of almost 46 nanomoles per liter. (…)

When it comes to supplements, the dose is sometimes given in international units, sometimes in micrograms. Here too, the conversion is simple: 100 international units of vitamin D correspond to 2.5 micrograms (1 microgram therefore corresponds to 40 IU). For example, 1000 IU would be 25 micrograms of vitamin D.

Why Germans have lower vitamin D levels than Americans

Back to the Harvard experiment and the question: Why do Americans have so much higher vitamin D blood levels than we do? This is because there is already a kind of basic supplementation in the USA: precisely because vitamin D is often lacking, it is also added to frequently consumed foods, such as milk and orange juice.

The test subjects in the Harvard experiment therefore had significantly higher vitamin D levels at the beginning of the experiment than the vast majority of Germans, and this at the middle age of 67, when there is often a pronounced deficiency in us and elsewhere.

In addition, precisely because vitamin D is so important, the participants were allowed to consume another 800 units of vitamin D daily on their own, even outside of the experiment. In other words, the control group was also allowed to supplement vitamin D, and in a decent dose. Under these circumstances, one would actually hardly expect a difference between the test and placebo groups!

On the surface, this didn’t exist either: the additional 2,000 units of vitamin D3 daily didn’t seem to have any effect on the participants on average (they already had high blood values). In any case, there were initially no differences compared to the control group.

Daily vitamin D3 reduced the risk of cancer

However, upon closer inspection, an interesting difference in the data could be seen. When the researchers looked at the body weight of the test subjects, they discovered the following:

However, overweight people in particular tend to need more vitamin D, partly because vitamin D is a fat-soluble vitamin that is stored in fat cells. The fatty tissue “swallows” part of the vitamin, so to speak, so that less vitamin D is left for the bloodstream and the various organs to develop its healing effects.

Higher supplementation doses may be necessary

Overall, this result suggests that vitamin D is not only essential for bone health, but could also play a role in other diseases, such as cancer, although this may require higher blood levels or supplement doses than those the body needs for healthy bones.

Basic studies confirm this assumption. Let’s assume we have a group of mice that get enough vitamin D from their food for healthy, strong bones – so the animals don’t suffer from mouse rickets. On the surface, one might think that these mice do not need additional vitamin D.

Harvard data: Vitamin could also protect against rheumatism

But that may not be true. Even in these mice, for example, cancer growth can still be significantly inhibited if they are provided with additional vitamin D. In a series of experiments, it was observed how existing tumors literally began to shrink just one week after the start of supplementation with the help of vitamin D supplementation.

Now, from a medical point of view, it is a long way from mice to humans – but the animal experiments could be viewed as further evidence that slightly higher doses of vitamin D could offer a certain degree of protection against cancer, which, by the way, seems to apply above all to the common forms of breast, prostate and colon cancer.

In addition, vitamin D could have a beneficial protective effect on other diseases. Further analysis of the Harvard data shows that supplementation of 2,000 IU daily, for example, also reduced the risk of autoimmune diseases, such as rheumatism, in the test subjects.