New research has found significant differences between the two types of vitamin D, with vitamin D2 having a questionable impact on human health. However, the study found that vitamin D3 could balance people’s immune systems and help strengthen defences against viral infections such as Covid-19. 

In a collaborative study by the Universities of Surrey and Brighton, researchers investigated the impact of vitamin D supplements – D2 and D3 – taken daily over a 12-week period on the activity of genes in people’s blood. 

Contrary to widely held views, the research team discovered that both types of vitamin D did not have the same effect. They found evidence that vitamin D3 had a modifying effect on the immune system that could fortify the body against viral and bacterial diseases.  

Professor Colin Smith, lead-author of the study from the University of Surrey, who began this work while at the University of Brighton, said: 

“We have shown that vitamin D3 appears to stimulate the type I interferon signalling system in the body – a key part of the immune system that provides a first line of defence against bacteria and viruses. Thus, a healthy vitamin D3 status may help prevent viruses and bacteria from gaining a foothold in the body.  

“Our study suggests that it is important that people take a vitamin D3 supplement, or suitably fortified foods, especially in the winter months.” 

Although some foods are fortified with vitamin D, like some breakfast cereals, yoghurts, and bread, few naturally contain the vitamin. Vitamin D3 is produced naturally in the skin from exposure to sunlight or artificial ultraviolet UVB light, while some plants and fungi produce vitamin D2.  

Many people have insufficient levels of vitamin D3 because they live in locations where sunlight is limited in the winter, like the UK. The Covid-19 pandemic has also limited people’s natural exposure to the sun due to people spending more time in their homes.  

Professor Susan Lanham-New, co-author of the study and Head of the Department of Nutritional Sciences at the University of Surrey, said: 

“While we found that vitamin D2 and vitamin D3 do not have the same effect on gene activity within humans, the lack of impact we found when looking at vitamin D2 means that a larger study is urgently required to clarify the differences in the effects. However, these results show that vitamin D3 should be the favoured form for fortified foods and supplements.”

In recent years, three meta-analyses of clinical studies have come to the conclusion that vitamin D supplementation was associated with a reduction in the mortality rate from cancer of around 13 percent. Scientists at the German Cancer Research Center (DKFZ) have now transferred these results to the situation in Germany and calculated: If all Germans over the age of 50 were to take vitamin D supplements, up to 30,000 cancer deaths per year could possibly be avoided and more than 300,000 years of life could be gained – in addition, health care costs could be saved.

For several years now, scientists have been investigating the influence of an adequate supply of vitamin D on the prognosis of numerous diseases. The focus is particularly on inflammatory diseases, diabetes, respiratory diseases and cancer.

Three meta-analyses of large clinical studies have been published in recent years on the question of how vitamin D supply affects cancer mortality rates. The studies* came to the same conclusion: cancer mortality is reduced by around 13 percent with vitamin D supplementation – across all cancers. Only methodologically high-quality randomized trials from all parts of the world were included in the meta-analyses. Exactly what biological mechanisms might underlie this is not yet clear.

“In many countries around the world, the age-adjusted rate of cancer mortality has fortunately declined over the past decade,” says Hermann Brenner, an epidemiologist at the German Cancer Research Center (DKFZ). “However, given the often considerable costs of many new cancer drugs, this success has often come at a high price. Vitamin D, on the other hand, is comparatively inexpensive in the usual daily doses.”

Vitamin D deficiency is common in the elderly population and especially among cancer patients. Brenner and colleagues now calculated what costs would be incurred by vitamin D supplementation of the entire population of Germany from the age of 50. They contrasted this sum with the potential savings for cancer therapies, which are often associated with costs in the range of several 10,000 euros, particularly in the case of advanced cancers during the last months of patients’ lives.

The scientists based this calculation on a daily administration of 1,000 international units of vitamin D at a cost of 25 euros per person per year. In 2016, approximately 36 million people over the age of 50 lived in Germany, resulting in annual supplementation costs of 900 million euros.

The researchers took the cost of cancer treatment from the scientific literature, assuming mean additional treatment costs of €40,000 for the last year of life. A 13 percent reduction in cancer mortality in Germany corresponded to approximately 30,000 fewer cancer-related deaths per year, the treatment costs of which amounted to €1.154 billion in the model calculation. Compared with the costs of vitamin supplementation, this model calculates an annual saving of €254 million.

The researchers determined the number of years of life lost at the time of cancer death using data from the German Federal Statistical Office. Brenner considers the costs and effort of a routine determination of the individual vitamin D level to be dispensable, since an overdose is not to be feared with a supplementation of 1000 international units. Such a prior testing had not been made in the clinical trials either.

“In view of the potentially significant positive effects on cancer mortality – additionally combined with a possible cost saving – we should look for new ways to reduce the widespread vitamin D deficiency in the elderly population in Germany. In some countries, foods have even been enriched with vitamin D for many years – for example, in Finland, where cancer mortality rates are about 20 percent lower than in Germany. Not to mention that there is mounting evidence of other positive health effects of adequate vitamin D supply, such as in lung disease mortality rates,” says Brenner, adding, “Finally, we consider vitamin D supplementation so safe that we even recommend it for newborn babies to develop healthy bones.”

To improve one’s vitamin D levels at absolutely no cost, DKFZ’s Cancer Information Service recommends spending time outdoors in the sunshine, two to three times a week for about twelve minutes. Face, hands and parts of arms and legs should be uncovered and without sunscreen for this period of time.

A new study in the Oxford Economic Papers finds that migration flows the last 500 years from high sunlight regions to low sunlight regions influence contemporary health outcomes in destination countries.

The researchers here noted that people’s ability to synthesize vitamin D from sunlight declines with skin pigmentation, and that vitamin D deficiency is directly associated with higher risk of mortality, from illnesses including cardiovascular disease, type 1 and type 2 diabetes, hypertension, and certain cancers. Recent research even .finds that vitamin D affects the severity of COVID-19.

Researchers here focused on groups from high sunlight regions that migrated to low sunlight regions between 1500 and today. The resulting population shifts caused the risk of vitamin D deficiency to rise substantially. The researchers explored the aggregate health consequences of such migration over a long historical perspective.

Researchers here constructed a measure that proxied the risk of vitamin D deficiency in a given population. The measure tracked the difference between sunlight intensity in the ancestral place of residence of the population, as well as the actual level of sunlight intensity at the place of current residence.

Using the difference between ancestor and ambient sunlight as a measure of the potential risk of vitamin D deficiency, researchers then examined its explanatory power in relation to life expectancy around the world. Researchers found that greater risk of vitamin D deficiency is negatively correlated with life expectancy, all else equal.

Researchers here noted that today there is widespread awareness of the harmful effects of excessive exposure to sunlight, which leads people to try to prevent sunburn through methods like sunscreen and limited outdoor exposure. Effective treatments of skin cancer are also widely available. People also spend more time indoors than their prehistoric ancestors, which lowers their exposure to sunlight. Consequently, the risk of premature death due to excessive sun exposure has decreased since prehistoric times.

However, the lower exposure times to sunlight increases the risk of vitamin D deficiency, particularly in people with higher skin pigmentation, whose ancestors came from high sunlight regions.

Ultimately the researchers here concluded that a migration-induced imbalance between the intensity of skin pigmentation and ambient sunlight can both relate and explain present-day global health differences: .Low sunlight regions that have received substantial immigration from high sunlight regions experience lower life expectancy than would have been the case in the absence of such migration flows.

“This research is important because it is the first research to document a link between an increased risk of vitamin D deficiency and differences in life expectancy across countries and regions. It thus serves to highlight the potentially huge benefit in terms of additional life years of taking vitamin D supplements, particularly during the autumn and winter” said author Dr. Thomas Barnebeck Andersen.

In humans, vitamin D is formed in the skin following its exposure to sunlight. In comparison to the body’s own formation of vitamin D, dietary consumption generally makes up only a relatively small proportion of the vitamin D supply to the body. While an overdose resulting from the body’s own production is not possible, it certainly can result from the consumption of highdoses of vitamin D – such as via certain food supplements.

An overdose of this kind leads to elevat ed calcium values in blood serum (hyperc alcaemia). The clinical symptoms associated with hypercalcaemia in humans range from fatigue and muscular weakness to vomiting and constipation, and can even lead to cardiac arrhythmias and the calcification of blood vessels. If persistent, hypercalcaemia can lead to kidney stones, kidney calcification and, ultimately, to a loss of renal function.

Even without exposure to sunlight, a daily consumption of 20 μg of vitamin D is adequate to meet the body’s needs for this vitamin for the vast majority (97.5%) of the population.

The European Food Safety Authority (EFSA) has set a UL value (tolerable upper intake level) of 100 μg for vitamin D. According to the latest scientific research, if adults and children aged eleven and older consume a daily quantity of no more than 100 μg, any impairments to health are unlikely. This UL value includes the intake of vitamin D from all sources, and thusincludes intake from supplements, normal dietary intake and intake from food that has been fortified with vitamin D. If high-dose vitamin D preparations are also consumed, this figure may be exceeded in combination with other sources of the vitamin.

From the perspective of nutritional science, the daily consumption of vitamin D preparations containing a 50 μg or 100 μg dose is not necessary. On the other hand, the BfR considers it unlikely that impairments to health will result from the occasional consumption of such high-dose preparations. If such high-dose vitamin D products are consumed on a daily basis over a longer period of time, however, the latest research does point to an elevated risk to health.

The BfR notes that, given an adequate length of time spent outdoors with corresponding exposure of the skin to sunlight, plus a balanced diet, an adequate supply of Vitamin D can be achieved by individuals without having to take vitamin D preparations. Individuals in risk groups for which a serious lack of vitamin D or a vitamin deficiency requiring medical intervention may be more likely to occur, should first clarify any need to take such preparations with their attending physician or general practitioner.

This opinion does not constitute a decision as to whether or not a product should be classified as a foodstuff, nor should it be interpreted as such.