It started exactly one year ago - the corona pandemic. It presented humanity with previously unknown challenges and brought with it not only a great deal of uncertainty, but also a huge information chaos and a lot of misinformation. There was often speculation about which measures would reduce the likelihood of infection with Covid-19 or prevent serious courses of the disease. And it was precisely in this discussion that a vitamin often came up - vitamin D. To this day, this vitamin is on everyone's lips. On the one hand, the sunshine vitamin is important for the health of bones and muscles. On the other hand, it contributes to the normal functioning of the immune system. And that is exactly the topic that is very relevant for all of us, especially in these times. This blog post is intended to give you the opportunity to acquire basic knowledge about this vitamin.
What exactly is vitamin D and what is it good for?
Vitamin D is a fat-soluble vitamin that is produced by the body when the skin comes into contact with sunlight. The human body is heavily dependent on the sun, as between 75% and 90% of the body's vitamin D is produced in response to sunlight, or more precisely, UV-B radiation. A further 10-20% of the vitamin can also be absorbed through food. However, it should be noted that the concentration in foods containing vitamin D is very low and therefore not sufficient to completely supply the organism! In central Europe in particular, a lack of sunlight can quickly lead to a vitamin D deficiency, especially in winter. Strong sun protection can also reduce vitamin D production in the body.
However, it is really important for the organism that there is a sufficient level of vitamin D in the organism and that the need - if this is not the case - is covered by supplements if necessary. This is because the vitamin is responsible for a variety of functions in the body. The most well-known function is supporting bone metabolism. Among other things, vitamin D promotes the absorption - i.e. the uptake - of calcium and phosphate from the intestine and is also responsible for the incorporation of these substances into the bones. This means that the vitamin plays a crucial role in bone mineralization! The vitamin is also involved in a number of metabolic processes and in the formation of various proteins, as well as the control of certain genes.
But that's not all, because vitamin D also contributes to the normal functioning of the immune system. The vitamin may also play a role in the body's immune response to respiratory viruses (such as Covid-19), but the evidence here is still insufficient and therefore not clear.
Are there differences in vitamin D?
Vitamin D belongs to a group of fat-soluble vitamins, the calciferols , which includes vitamins D1 to D5. However, there are significant differences in effectiveness between these subtypes. Vitamin D3 differs from the rest of the D vitamins in that it is the only vitamin produced naturally in the body - the other D vitamins are therefore artificially produced vitamins. Vitamin D3 is advantageous in that, in contrast to the other D vitamins, it has a higher bioavailability, which means it can be absorbed more easily by the body and thus works better. When buying vitamin D preparations, you should therefore make sure to choose vitamin D3 supplements.
What are the symptoms of a vitamin D deficiency?
Factors that contribute to a vitamin D deficiency include climatic conditions. This means that unfavorable weather conditions and thus low UV-B radiation can be the reason for reduced absorption of the vitamin - even in the summer months. In addition, the altitude, the daily amount of sunshine, the ozone content in the air and also air pollution play a role.
But the absorption of vitamin D depends not only on the outside world, but also on the body's own factors. These include, for example, age, skin color, weight and lifestyle. Especially under the current circumstances in which people leave their homes as little as possible, a vitamin D deficiency can quickly occur because the body receives less sunlight than under normal conditions. This also means that the time you spend indoors or your leisure activities have an influence on the vitamin D levels in your body.
Vitamin D plays an important role in bone health - a deficiency can therefore lead to decalcification of the bones (although this tends to happen in severe cases). Other symptoms of a deficiency include a decrease in bone density, bone pain and disruption of calcium and phosphate metabolism. In addition, a low vitamin D level can lead to poorly healing bone fractures, respiratory infections, depression and mood swings.
In general, when measuring vitamin D levels, it is important to remember that these are subject to strong seasonal fluctuations. So if you have your vitamin D levels measured once and the reading is low, this does not necessarily mean that you are suffering from a long-term vitamin D deficiency.
How much vitamin D does the body need?
Among other things, vitamin D saturation in the blood is highly dependent on location. The American doctor and author Dr. Michael Greger writes in his bestseller “How not to die” about foods that keep the body healthy and prevent disease in the long term. Here he recommends vitamin D supplementation for people who live at a latitude above 50 degrees (e.g. Moscow, London and Berlin). This is because the “vitamin D winter” can last up to six months of the year here and the natural absorption of the vitamin through the sun is therefore too low.
The NRV - Nutrients Reference Value - for vitamin D in the body is 5 micrograms for daily intake. The NRV is a guideline for the recommended daily intake of nutrients.
Meanwhile, the British government recommends taking a daily vitamin D supplement of 10 micrograms between October and early March to ensure a healthy vitamin D level in the body. For some subgroups, especially older people, this recommendation even applies all year round.
Vitamin D and the Immune System
As already explained, vitamin D not only affects bone health, but also metabolism and the immune system. This can lead to a vitamin D deficiency, especially in times of little sun and during periods of lockdown. This in turn can have consequences for our immune system and impair the performance of the immune system. Older people are particularly affected by this, as the skin's ability to produce vitamin D decreases with age.
In the study “the vitamin D receptor and T cell function”, a Danish research team explains the interactions between vitamin D and the human immune system. They come to the conclusion that the vitamin activates important cells of the immune system - so-called killer cells. As the name suggests, these have the task of fighting pathogens and toxins in the organism.
This means that if there is too little vitamin D in the body, the killer cells in the body are less activated and the immune system is therefore less effective. A weaker immune system in turn means that pathogens can penetrate the organism more easily and you get sick more quickly.
