It’s winter – so there are fewer hours of sunshine every day. And because it’s lockdown time again, many people spend even more time at home than in the uncomfortable time of the year. This also triggers a discussion among medical professionals and scientists about “that some people may not get the physiological vitamin D levels they need from sunlight,” like this week, for example in an editorial in the journal “The Lancet” was noted.
The influence of vitamin D on the body is much debated. It has been proven that good vitamin D status has beneficial effects on bone health – and a deficiency could therefore have problematic effects. But does taking additional preparations in the case of a vitamin D deficiency also have a preventive effect on other diseases? There are numerous observational studies on this, but little conclusive evidence. Since the beginning of the pandemic, researchers have also been looking for possible connections between a vitamin D deficiency and the severity of a Covid 19 infection. The problem: So far there is no clear data situation.
Reduce Covid-19 risk with vitamin D?
The German Nutrition Society has now differentiated its knowledge of vitamin D more strongly. According to this, there is still no evidence that vitamin D protects against cancer, cardiovascular diseases and type 2 diabetes mellitus, “said Prof. Jakob Linseisen, President of the German Nutrition Society quoted in a December communication. These are also risk factors for a more severe course of Covid-19. Only connections are observed.
With a view to the study situation, “an inverse relationship” has so far been observed between the vitamin D status and the risk of acute respiratory infections. In other words, researchers have observed that the lower the vitamin D status, the higher the risk of respiratory infections. So far, however, there is no evidence of a causal relationship between the findings here either. The same was found in dementia and depression, but not in asthma, MS and type 1 diabetes mellitus.
So it is not surprising that after a year of pandemic the connection with Covid-19 has not yet been adequately explored. “Conclusions for the prevention of Covid-19 cannot currently be drawn from the data, however, since all of the studies assessed were carried out before the pandemic occurred,” according to the specialist society.
The Federal Institute for Risk Assessment also made it explicitly clear at the end of October 2020 that no studies are known that prove that taking vitamin D protects against infection with the coronavirus. Only in the case of a deficiency could a supplementary intake of vitamin D have a positive influence on the prevention of acute respiratory infections, summarizes the German Nutrition Society.
Lockdown: UK recommends daily vitamin D intake for citizens
As a rule, the body produces 80 to 90 percent of the vitamin itself in the skin – with the help of sunlight, or more precisely: UV-B radiation. It is necessary to stay outdoors. “It is not enough to stay in a bright room, because the UV-B components in sunlight cannot penetrate through the glass in window panes,” it says in one Profile of the Robert Koch Institute. Most countries now have lockdowns, exit restrictions, home offices and closed schools – which is why a lot of time is spent at home.
Great Britain’s health authorities are therefore giving new recommendations in view of the pandemic conditions – and have started a vitamin D offensive. “During the fall and winter months, everyone in the UK is advised to take vitamin D supplements every day to support general health, and particularly bone and muscle health,” it said in the UK Department of Health’s amended guidelines. “Many of us were inside more than usual this year and may not have made enough vitamin D from sunlight.” The UK government is also offering 2.7 million particularly vulnerable people, for example from nursing homes, a free 10 microgram daily dose this winter Vitamin D as a dietary supplement.
According to the RKI, diet contributes only a relatively small proportion to the vitamin D supply with an estimated proportion of around ten to 20 percent. Few foods contain significant amounts of vitamin D – for example fatty sea fish, certain offal, certain edible mushrooms and eggs. In addition to natural sources, vitamin D can therefore also be supplied through food supplements – so-called supplements – and fortified foods. The Federal Institute for Risk Assessment but recommends no more than 20 micrograms of vitamin D per day.
Too much vitamin D intake through dietary supplements is unhealthy
In addition to a deficiency, vitamin D poisoning can also occur. According to the RKI, this cannot happen through the body’s own vitamin D production and natural nutrition. However, it can become problematic with “excessively high intake of supplements (food supplements), high-dose medication, high consumption of fortified foods”.
Then increased calcium levels develop in the body, which can acutely lead to nausea, loss of appetite, abdominal cramps, vomiting or in severe cases to kidney damage, cardiac arrhythmias, unconsciousness and death. “Since vitamin D can be stored in the body, a gradual overdose is possible in addition to an acute one,” explains the RKI. In other words, if at all possible, the best thing to do is to take a short walk to the front door.