What is vitamin D and where does it occur?
Vitamin D is a fat-soluble vitamin that is relatively heat-resistant, but can be damaged by exposure to light and oxygen. Food can only supply a small part of the daily requirement, but our body can produce vitamin D itself through the action of UV radiation (sunlight).
Nowadays the effect of vitamin D can be demonstrated in more than 30 tissue types, therefore this vitamin plays an important role for the various metabolic functions. In this role,, it also works closely with its partner magnesium in our system, which is why the supply of vitamin D and magnesium together should always be considered.
The same applies to vitamin K, and the more bioactive K2 that we need for the function of the proteins that vitamin D stimulates. Vitamins D and K together also control calcium intake much better than on their own, which is why they are often taken as pairs, especially for bone health.
Vitamin D is a fat-soluble vitamin which is relatively heat-resistant but can be damaged by exposure to light and oxygen. Unfortunately only a small part of our need can be absorbed through food. However, our body is capable of producing vitamin D itself through the exposure to UV radiation (sunlight).
The UV rays absorb provitamin D into the skin and then convert it into cholecalciferol (vitamin D3). If vitamin D is absorbed through food, it already possesses the cholecalciferol structure.
Vitamin D can be found in the form of cholecalciferol (vitamin D3) or as provitamin 7-dehydrocholesterol in animal foods. Liver and fatty fish, such as salmon or herring, contain higher vitamin D concentrations. Egg yolk, milk and dairy products, on the other hand, have lower quantities. Vegetarian sources are rather insignificant for sufficient vitamin D intake. Only yeasts, mushrooms, spinach and some cabbage vegetables contain traces of vitamin D2 (ergosterol).
Since vitamin D can be absorbed through nutrition as well as through solar radiation, it occupies a special position among vitamins. Notably, one cannot achieve a sufficient supply of vitamin D through nutrition alone. The recommended level is at least 75nmol/l in our blood. By spending enough time in the sun, the desired supply can be achieved without supplementation. However, prolonged sun exposure could lead to disadvantages such as skin aging or even skin cancer.
Even in summer, the radiation is too low after about 4 PM, meaning spending time outside after work cannot adequately boost vitamin D production.
North of the world’s 42nd parallel, vitamin D cannot be absorbed in sufficient amounts during the winter. One small trick to know whether the current sunlight is able to give you sufficient amounts of vitamin D is to take a look at your own shadow. If the shadow is longer than you are, the sun’s intensity is too low.
Ultimately, this means that in many countries vitamin D synthesis is not possible for nearly half a year. However, even in the summer the radiation is too low after 4 PM, which is why a stay outside after work cannot contribute anything to vitamin D production. This makes it more critical to spend some time in the sun during the middle of the day, perhaps on a lunch break. This can be difficult to do, which leads to the necessity of further vitamin D supplementation year round.
Insufficient vitamin D status is associated with a higher risk of various diseases.
Why do we need vitamin D?
Insufficient vitamin D status is associated with a higher risk of various diseases, such as prostate, colon, or breast cancer.
The occurrence of cardiovascular diseases, diabetes mellitus, osteoporosis, or multiple sclerosis can also be associated with vitamin D deficiency.
Vitamin D is important for bone metabolism. It is responsible for regulating the calcium and phosphate balance, as well as for calcium transport and absorption from the intestines. It also contributes to bone hardening and mineralization. It also reduces blood pressure, supports the immune system, has anticarcinogenic properties, and protects the pancreas.
Who needs extra vitamin D?
According to the German Consumption Study of 2008, 82% of men and 91% of women do not consume enough vitamin D through diet, which is why vitamin D is officially considered a critical nutrient.
A regular intake of 20 – 25 μg/d Vitamin D is an ideal amount to overcome a vitamin D deficiency. Infants, young children, older people, and people with chronic intestinal and kidney diseases need a high amount of vitamin D. Asthmatics, diabetics, and MS patients are also advised to supplement their intake with vitamin D.
If you use sunscreen with a higher sun protection factor (more than SPF 20), then you should consider vitamin D supplementation. Special risk groups for a deficiency are also vegans and vegetarians, as well as people with dark skin, residents of a nursing home, chronically ill people, and those who spend most of their day indoors.
Vitamin D has a positive effect on the heart and blood vessels
Unfortunately, a vitamin D deficiency often particularly affects people who already have health problems. For example, a Brazilian study showed that patients with type 2 diabetes and high blood pressure suffer particularly frequently from vitamin D deficiency. The researchers also found a link between vitamin D status and blood pressure.
Vitamin D can also have a positive effect on the heart and blood vessels, especially the elasticity of the arteries is improved. This was the result of a study by Augusta University in Georgia, USA. Overweight people were given various vitamin D doses or a placebo preparation for over 16 weeks. Even at low doses, enormous differences in arterial flexibility were observed compared to the placebo group.
Vitamin D increases muscle strength
Vitamin D also plays a crucial role in maintaining muscle function. Studies have also shown a positive correlation between vitamin D status and muscle function. This preservation of performance is particularly important for seniors, as vitamin D can reduce the risk of dangerous falls from a height.
Vitamin D status is also an important issue for competitive athletes. A study by the University of Copenhagen showed that 45% of Danish elite swimmers were found to have inadequate vitamin D levels. Athletes with a higher status showed much better muscle performance than their undernourished teammates.
A Finnish study found a 113% higher risk of regular headaches due to vitamin D deficiency.
Vitamin relieves headache and depression
A study by the University of Kuopio, in which 2,600 Finnish men were examined, showed that a low vitamin D status was also associated with a higher headache frequency. The probability of pain was 113% higher in the group with the lowest values than in the best-nourished participants.
Another study by the same research centre, involving 1,600 subjects, also found a link between vitamin D deficiency and symptoms of depression. Due to its geographical location in the far north with long, sunless winters and the associated frequent vitamin D deficiencies, Finland is a centre of research on this topic.
There is also a link between vitamin D deficiency and the extent of irritable bowel symptoms.
According to a meta-study with data from over 44,000 participants, good vitamin D status in cancer patients slowed the course of the disease and reduced mortality by 26%.
Tumor cells do not like vitamin D
More and more studies also point to the anticarcinogenic effect of vitamin D. A new study from Japan with 7,000 test persons found out that a high Vitamin D supply reduces the total risk of developing cancer, with a special effect on the risk of liver cancer.
An overview analysis of 64 studies at the University of Edinburgh came to similar conclusions and described that a high vitamin D content is associated with a 16% reduction in disease progression in cancer patients and a 26% reduction in mortality.
Who needs additional vitamin D?
According to the 2008 German Consumption Study, 82% of men and 91% of women do not consume enough vitamin D in their diet, which is why vitamin D is officially considered a critical nutrient.
A regular intake of 20 – 25 μg/d vitamin D is an ideal way to normalise an insufficient vitamin D status. An increased need at Vitamin D have above all infants and small children, in addition to older persons, as well as persons with chronic intestine and kidney illnesses. An additional supply of vitamin D is also recommended to asthmatics, diabetics and MS patients.
If a strong sun protection factor (SPF 20 or higher) is applied during a stay in the sun, a replacement should also be considered. Special risk groups for a deficiency are in particular vegans and vegetarians, as well as persons with dark skin color, inhabitants of a nursing home or old people’s home and chronically ill persons – not to forget persons, who stay mostly indoors due to work.
