Vitamin D is said to have almost miraculous healing powers: it is not only supposed to protect against colds, flu and osteoporosis, but also against cancer. One thing is certain: many people develop a vitamin D deficiency, especially in winter. FITBOOK clears up the myths surrounding the sun hormone and explains when doctors start talking about a deficiency and how it can be prevented.
While most people are very familiar with vitamins A, C and E, vitamin D has long been one of the lesser known. Many people now know about the importance of the vitamin, which is actually a hormone. However, when it comes to functions and occurrence in food, there is still a lack of clarity. You should definitely keep an eye on this vitamin, because a deficiency can easily occur, especially in winter. This in turn can have negative consequences for the immune system and the bones. That’s why FITBOOK has compiled everything you need to know about vitamin D below and spoke to a real expert.
What exactly is vitamin D?
There are several variants of vitamin D: D1, D2 and D4. However, only the D3 is vital. This is not really a vitamin, as it can also be produced by the body itself. That is why it is also known as D-hormone or sun hormone. A prerequisite for the body’s own production, however, is sufficient sunlight.
Is there enough sunlight for production?
It is not easy to produce enough vitamin D from the sun’s rays. “A certain radiation intensity is necessary for this process. Depending on the position of the sun in the morning and evening, this is not reached even in the summer months. In our latitudes, the necessary radiation intensity is not reached even at noon in the winter half-year, so that we cannot produce vitamin D with the help of sunlight between mid-October and mid-April,” says nutritionist Prof. Dr. Nicolai Worm.
If we expose our skin to the sun, the UVB radiation causes a synthesis of pro-vitamin D3 in the skin cells. The body cannot yet utilize this, but stores it in fat and muscle tissue as inactive D3. Another precursor is formed for long-term storage in the liver. This inactive circulating and storage form of vitamin D is called calcidiol or 25(OH)D3. It is only in the kidneys (and decentrally in the individual cells) that active D3, the so-called hormone calcitriol, is produced from this, which the body can finally utilize. For the sake of simplicity, we will use the generic term vitamin D below.
The hormone is stored in muscle and adipose tissue. If you fill your storage well in summer, you can draw on it for several months in winter. «However, since most people today do not use the sun properly in summer because they work indoors and apply sunscreen, up to 80 percent of Germans develop a vitamin D deficiency in the winter months,» explains expert Prof. Worm. So if you always wear sunscreen in summer, you prevent sunburn, but you also inhibit vitamin D production.
In order to achieve an optimal supply from the sun, there is a rule of thumb. Read here what you need to consider:
What is the daily requirement?
Since the body is able to produce vitamin D, it is difficult to give a recommendation on how much to take in from the outside. The German Society for Nutrition (DGE) therefore gives estimates for the case that no vitamin D production takes place in the body.
What foods is it found in?
You can get vitamin D from food, but that’s not easy either, because only high-fat fish such as salmon, herring and mackerel contain sufficiently high amounts of it. Would you like a small example? You would have to eat between 100 and 200 grams of salmon a day to meet your needs.
Smaller amounts are also found in other foods, including mushrooms and eggs.
Vitamin D in selected foods
To meet your daily vitamin D needs, you would have to eat fatty fish, such as salmon, almost every dayPhoto: Getty Images
What is the function of vitamin D and what does a deficiency cause?
Vitamin D is best known in connection with bones because it strengthens the skeleton and thus protects against osteoporosis, i.e. age-related bone loss. «If you press on your shin with your thumb and this causes significant pain, you should definitely have your bone health checked by an orthopedist and your vitamin D level determined,» recommends Prof. Worm. But according to our expert, symptoms such as tiredness, listlessness and depressive moods can also indicate a deficiency.
“Vitamin D is activated in the body into a hormone that can turn on hundreds of genes in our cells in various tissues and organs. This means that if there is a deficiency, these genetic predispositions cannot develop,” says the nutritionist.
But the effect goes much further. In 2010, researchers at the University of Copenhagen found out that vitamin D is a kind of booster for the immune system.1 And it works as follows: When a T helper cell (which is crucial for the immune system) comes into contact with a bacterial cell, it begins to produce a vitamin to produce D-recognition protein. This allows the T cell to recognize whether the vitamin is available in the blood. If it is found, a whole chain of reactions takes place, with hundreds of identical T cells forming in the fight against the pathogen found. If, on the other hand, there is a deficiency, the strengthening of the immune system unfortunately fails.
Vitamin D levels and cancer risk – study situation
The link between vitamin D and cancer has been the subject of research for many years. So far, there is no evidence that taking it can prevent cancer. However, vitamin D appears to have an effect on the likelihood of developing progressive (metastatic and fatal) cancer. This is indicated by findings by US researchers published in the JAMA Network.2 They found that vitamin D was associated with a 17 percent risk reduction for advanced cancer. In participants with a normal body mass index, the risk reduction was even higher (38 percent).
According to a study by the German Cancer Research Center (DKFZ) in Heidelberg, 30,000 cancer deaths could be prevented in Germany if the elderly population were adequately supplied with vitamin D.3
Is there a connection with Covid-19 courses?
There seems to be a connection between the course of a corona infection and the vitamin D status. Some studies suggest so. Apparently, a low level has a negative impact on the probability of survival, according to the studies, a good level could have a positive effect on the course of the disease.
Should you take vitamin D as a supplement?
Only the doctor can determine whether you are suffering from a deficiency using a blood analysis. If this is the case, you should – in consultation with your doctor – take food supplements. A check-up can then be used to determine whether the preparation is working and whether the blood value has increased.
Also interesting: Everything you need to know about vitamin A
How high should the vitamin D level in the blood be?
The range of guide values is relatively large: According to the Federal Institute for Risk Assessment (BfR), one speaks of vitamin D deficiency at serum concentrations of the marker 25-hydroxyvitamin D below 30 nanomoles per liter of serum (30 nmol/l). This corresponds to 12 nanograms per milliliter of serum (12 ng/ml). A good or adequate vitamin D supply in relation to bone health is when the blood concentration of this marker is at least 50 nmol/l (or 20 ng/ml).
In the absence of endogenous vitamin D formation, an adequate vitamin D supply is achieved with an intake of 20 micrograms per day. This corresponds to 800 units (i. E.), which can be taken permanently without fear of damage to health. The BfR specifies 4000 as the «upper tolerable limit». E. per day.
However, our expert is critical of the general recommendations: “My personal situation shows how absurd this recommendation is on an individual level: I need 4,000 i per day in the winter months. E. to maintain a 25-hydroxyvitamin D level of 35-40 ng/ml. This puts me statistically in the area of the lowest risk for all lifestyle diseases. If I 5,000 i. E., I would perhaps get a value of 40-45 ng/ml and would therefore already be ‘poisoned’ according to the BfR – but in reality still within the ideal range. Others like with 4,000 i. E. can already reach significantly higher blood levels per day – but it is unlikely that the dangerous range of over 100 ng/ml will be reached,” says Prof. Worm.
Conclusion
Whether an additional intake of the sun hormone can prevent colds, flu, bone diseases as well as prostate, breast and colon cancer has not been clearly clarified. “These are all multifactorial diseases, for which there is no single cause. Whether vitamin D can help individually cannot be answered – but a deficiency is a risk factor for these diseases. This means that you increase the likelihood of developing such diseases. Conversely, good care reduces the likelihood of contracting the disease – but you are still not immune to it,” sums up Prof. Nicolai Worm. In any case, you should have your vitamin D blood level checked by a doctor – and only take a dietary supplement if there is a deficiency.
Sources:
1. von Essen MR, Kongsbak M, Schjerling P, Olgaard K, Odum N, Geisler C. Vitamin D controls T cell antigen receptor signaling and activation of human T cells. Nat Immunol. (April 2010);11(4):344-9. doi: 10.1038/ni.1851. Epub (2010). PMID: 20208539.
2. Chandler PD, Chen WY, Ajala ON, et al. Effect of Vitamin D3 Supplements on Development of Advanced Cancer: A Secondary Analysis of the VITAL Randomized Clinical Trial. JAMA Netw Open. (2020);3(11):e2025850. doi:10.1001/jamanetworkopen.2020.25850
3. Niedermaier T, Gredner T, Kuznia S, Schöttker B, Mons U, Brenner H. Vitamin D supplementation to the older adult population in Germany has the cost-saving potential of preventing almost 30 000 cancer deaths per year. Mol Oncol. (2021). doi: 10.1002/1878-0261.12924. Epub ahead of print. PMID: 33540476.
4. Schilling S: Epidemic vitamin D deficiency among patients in an elderly care rehabilitation facility. Dtsch Arztebl Int (2012); 109(3):33-8. DOI: 10.3238/arztebl.2012.0033