Exactly one year ago, it began – the coronavirus pandemic. It presented humanity with unprecedented challenges and brought not only a great deal of uncertainty but also massive information chaos and a lot of misinformation. There was frequent speculation about which measures would reduce the likelihood of Covid-19 infection or prevent severe courses of the disease. And in this discussion, one vitamin often came up – vitamin D. To this day, this vitamin is widely talked about. The sunshine vitamin is important for bone and muscle health on the one hand. On the other hand, it contributes to the normal function of the immune system. And that is exactly the topic that is very relevant to all of us right now. This blog post aims 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 the body produces when the skin comes into contact with sunlight. The human body is highly dependent on the sun because between 75% and 90% of the vitamin D in the body is produced in response to sunlight, specifically UV-B radiation. Another 10-20% of the vitamin can also be obtained through food. However, it should be noted that the concentration of vitamin D in foods is very low and therefore not sufficient to fully supply the body! Especially in Central European latitudes, vitamin D deficiency can occur quite quickly in winter due to a lack of sunlight. Strong sun protection can also reduce vitamin D production in the body.
It is really important for the body to have an adequate vitamin D level, and if this is not the case, the requirement should be met through supplements if necessary. This vitamin is responsible for a variety of functions in the body. The best-known function is supporting bone metabolism. Vitamin D promotes the absorption of calcium and phosphate from the intestine and is also responsible for incorporating these substances into the bones. This means that vitamin D plays a crucial role in bone mineralization! Additionally, the vitamin is involved in a number of metabolic processes, the formation of various proteins, and the regulation of certain genes.
But that’s not all, because vitamin D also contributes to the normal function of the immune system. It 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 conclusive.
Are there differences among the D vitamins?
Vitamin D belongs to a group of fat-soluble vitamins called calciferols, which include vitamins D1 through D5. However, there are significant differences in effectiveness among these subtypes. Vitamin D3 differs from the other D vitamins in that it is the only vitamin naturally produced in the body – the other D vitamins are artificially made. Vitamin D3 is advantageous because, unlike the other D vitamins, it has higher bioavailability, meaning it is more easily absorbed by the body and thus works better. When buying vitamin D supplements, you should definitely make sure to choose vitamin D3 supplements.
What are the symptoms of a vitamin D deficiency?
Factors that contribute to vitamin D deficiency include climatic conditions. This means unfavorable weather conditions and thus low UV-B radiation can be the reason for reduced vitamin D uptake – even in summer months. Altitude, daily sunshine duration, ozone content in the air, and air pollution also play a role.
But vitamin D uptake depends not only on external factors but also on internal factors such as age, skin color, weight, and lifestyle. Especially under current circumstances, where people leave their homes as little as possible, vitamin D deficiency can occur quickly because the body receives less sunlight than under normal conditions. This means that the time you spend indoors or how you spend your free time can influence your vitamin D levels.
Vitamin D plays an important role in bone health – a deficiency can lead to bone demineralization (though this usually happens only in severe cases). Other symptoms of deficiency include decreased bone density, bone pain, and disruption of calcium and phosphate metabolism. Additionally, low vitamin D levels can lead to poorly healing bone fractures, respiratory infections, depression, and mood swings.
In general, when measuring vitamin D levels, it should be noted that these are subject to strong seasonal fluctuations. So if you have your vitamin D level measured once and it is low, this does not necessarily mean you have 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 location-dependent. American doctor and author Dr. Michael Greger writes in his bestseller “How Not to Die” about foods that keep the body sustainably healthy and prevent diseases. He recommends vitamin D supplementation for people living above the 50th parallel (for example, Moscow, London, and Berlin). This is because the “vitamin D winter” can last up to six months a year in these regions, making natural vitamin D production from sunlight too low.
The NRV – Nutrient Reference Value – for vitamin D is 5 micrograms for daily intake. The NRV is a guideline for the recommended daily intake of nutrients.
Meanwhile, the British government advises 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 applies year-round.
Vitamin D and the immune system
As already explained, vitamin D affects not only bone health but also metabolism and immune defense. Especially in times with little sun and during lockdowns, vitamin D deficiency can occur. This, in turn, can affect our immune defense and reduce the immune system’s performance. Older people are particularly affected because 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 conclude that the vitamin activates important immune cells – so-called killer cells. As the name suggests, these cells are responsible for fighting pathogens and toxins in the body.
The implication is: if there is too little vitamin D in the body, the killer cells are less effectively activated, and thus the immune system is less efficient. A weaker immune defense means pathogens can more easily enter the body, and you become ill more quickly.
