Exactly one year ago, it began – the Corona pandemic. It presented humanity with unprecedented challenges, bringing not only a great deal of uncertainty but also immense information chaos and a great deal of misinformation. There was much speculation about which measures would reduce the probability of infection with Covid-19 or prevent severe cases. And in this discussion, one vitamin frequently came up – vitamin D. To this day, this vitamin is on everyone's lips. The sunshine vitamin is important for the health of bones and muscles. It also contributes to the normal function of the immune system. And that is precisely the topic that is very relevant for 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 produced by the body when the skin is exposed to sunlight. The human body is highly dependent on the sun, as between 75% and 90% of the body's vitamin D is produced in response to sunlight, specifically UV-B radiation. An additional 10-20% of the vitamin can also be obtained through food. However, it's important to note that the concentration of vitamin D in foods is very low and therefore insufficient to meet the body's needs. Especially in Central European latitudes, a lack of sunlight can quickly lead to a vitamin D deficiency, particularly during the winter months. Strong sunscreens can also reduce the body's vitamin D production.
It is crucial for the body to maintain sufficient vitamin D levels, and if necessary, supplementation may be required. This is because vitamin D is responsible for a multitude of functions in the body. Perhaps its best-known function is supporting bone metabolism. Vitamin D promotes the absorption of calcium and phosphate from the intestines and is also responsible for incorporating these substances into bones. This means that vitamin D plays a vital role in bone mineralization! Furthermore, vitamin D 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. The vitamin may also play a role in the body's immune response to respiratory viruses (such as Covid-19), but the evidence in this area is still insufficient and therefore not conclusive.
Are there differences in the D vitamins?
Vitamin D belongs to a group of fat-soluble vitamins called... Calciferols, which includes vitamins D1 to D5. However, there are significant differences in effectiveness between these subtypes. Vitamin D3 differs from the other D vitamins in that it is the only one naturally produced by the body – the other D vitamins are synthetically produced. Vitamin D3 is advantageous because, unlike the other D vitamins, it has a higher bioavailability, meaning it is more easily absorbed by the body and therefore more effective. When buying vitamin D supplements, you should therefore make sure to choose vitamin D3 supplements.
What are the symptoms of a vitamin D deficiency?
Factors that can contribute to vitamin D deficiency include climatic conditions. This means that unfavorable weather conditions and consequently low UV-B radiation can lead to reduced vitamin absorption – even in the summer months. Altitude, daily sunshine duration, ozone levels, and air pollution also play a role.
But vitamin D absorption depends not only on the external environment but also on internal factors. These include, for example, age, skin color, weight, and lifestyle. Especially under the current circumstances, where people are leaving their homes as little as possible, a vitamin D deficiency can quickly develop because the body receives less sunlight than under normal conditions. This also means that the time you spend indoors and your leisure activities can influence the vitamin D levels in your body.
Vitamin D plays a crucial role in bone health; a deficiency can therefore lead to bone demineralization (although this is more common in severe cases). Other symptoms of a deficiency include decreased bone density, bone pain, and impaired calcium and phosphate metabolism. Furthermore, low vitamin D levels can contribute to poorly healing bone fractures, respiratory infections, depression, and mood swings.
Generally, when measuring vitamin D levels, it's important to remember that these levels are subject to strong seasonal fluctuations. Therefore, if you have your vitamin D levels tested once and a low value is found, this doesn't necessarily mean you're 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 physician and author Dr. Michael Greger writes in his bestseller "How Not to Die" about foods that keep the body healthy in the long term and prevent disease. He recommends vitamin D supplementation for people living at latitudes above 50°C (for example, in Moscow, London, and Berlin). This is because the "vitamin D winter" can last up to six months of the year in these latitudes, and natural absorption of the vitamin through sunlight is therefore insufficient.
The NRV (Nutrient 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.
The British government, meanwhile, recommends taking a daily vitamin D supplement of 10 micrograms between October and early March to ensure healthy vitamin D levels in the body. For some subgroups, particularly older people, this recommendation applies year-round.
Vitamin D and the immune system
As previously explained, vitamin D not only affects bone health but also metabolism and the immune system. Especially during periods of low sunlight and lockdowns, a vitamin D deficiency can occur. This, in turn, can have consequences for our immune system and impair its effectiveness. Older people are particularly affected, as the skin's ability to produce vitamin D decreases with age.
In their 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 their name suggests, these cells are responsible for fighting pathogens and toxins in the body.
Consequently, this means that if there is too little vitamin D in the body, the body's killer cells are less effectively activated, and therefore the immune system is less efficient. A weakened immune system, in turn, makes it easier for pathogens to enter the body, and you become ill more quickly.
