Introduction
„Nutrients“ is the umbrella term for the various micro- and macronutrients. Nutrients in general are the building blocks that drive, maintain and repair our body. They play a central role in our body. Among other things, they are responsible for the following functions of our body:
- Energy supply
- energy regulation
- Growth and development
- Immune function
- Healthy skin, hair and nails
- Function of the nervous system
- Maintenance of muscle function
- Prevention of diseases
Nutrients are the foundation of a healthy life, which is why it is essential to eat a balanced diet that contains all the necessary nutrients in appropriate amounts. To this end, it is important to ensure a balanced diet and not to eat a one-sided diet in the long term, because if, for example, only one vegetable is eaten because it is perceived as particularly „healthy“, the daily diet becomes very one-sided, which will lead to deficiency symptoms in the long term.
As mentioned above, nutrients are seperated in micro- and macronutrients. These in turn are further subdivided into carbohydrates, proteins and fats, or minerals and vitamins (see Fig. 1), which in turn are subdivided into further subcategories (e.g. hormones) that are irrelevant for the further definition of vitamin D and are therefore not mentioned here.
Vitamin D Production
Vitamin D3 (is therefore one of the vitamins from the vitamin D complex. Like the vitamin complexes A, E and K, it is one of the fat-soluble vitamins. In the context of nutrition, it should therefore be men-tioned that it is particularly suitable to consume these vitamins together with a fat-containing diet, as this is the only way they can be absorbed and processed by the body.
It should also be noted that vitamin D3 is the only vital vitamin that the body cannot produce itself in sufficient quantities by synthesizing it from food. It is primarily formed by the irradiation of UV light on the skin and is also stored there, but only to a certain extent. During the summer months in Austria, the body can cover an average of around 80-90% of its vitamin D requi-rements, provided we spend enough time in the sun. Experts recommend spending 5-15 minutes in the sun, at least three times a week to ensure sufficient vitamin D production. In the winter months (November to February), however, there is not enough sunshine in our longitudes, while at the same time we spend less time in the fresh air, which is why today around 30% of adults have been shown to have a vitamin D deficiency in their blood. This makes vitamin D deficiency the most common deficiency disease in Austria. Although certain amounts of vitamin D can be stored in the skin, these buffer stores are usually used up relatively quickly in winter.
Natural Occurrence
In addition, a deficiency of calcitriol (the active form of the vitamin), as mentioned earlier, is difficult to compensate for through diet alone. Cereal and dairy products generally contain the most vitamin D2 and D3, which can be metabolized into the active form of the vitamin in the liver. Fatty fish, mushrooms, liver, and egg yolk also contain vitamin D3. Since vitamin D3 is a fat-soluble vitamin, it is important to ensure an adequate intake of healthy fats when consuming it. This allows the vitamin to be absorbed from the food and metabolized into calcitriol, the active form of the vitamin, in the liver and kidneys.
This active form is necessary to absorb calcium and phosphorus from the intestine, which are then incorporated into the bones to strengthen and densify them. This process is called mineralization and occurs at every age, but is particularly pronounced during bone formation, growth, and repair. This is why children and adolescents in the growth phase, as well as seniors, have an increased need for vitamin D.
What is Vitamin D3 for?
As early as 2016, the Robert Koch Institute (RKI) determined that 30.2% of all German citizens have a severe vitamin D deficiency (< 30 nmol/l). A moderate vitamin D deficiency (< 50 nmol/l) was even found in 61.5% of study participants. The RKI also differentiates between seasons, with over 80% of people in Germany having a moderate vitamin D deficiency in winter and over 50% having a severe vitamin D deficiency. The fact that this is problematic becomes clear when you take a closer look at what our body needs vitamin D for.
Vitamin D2 and vitamin D3 are converted to calcitriol, the active form of the vitamin, in the liver and kidneys. This absorbs the minerals phosphorus and calcium from the intestine in order to incorporate them into bones and thus compact them (mineralization).
In addition to bone stability, the vitamin also plays a major role in the immune system. Leukocytes, the white blood cells that are responsible for part of the immune defense, are occupied by vitamin D receptors. Basic research confirms that vitamin D has an immunomodulating effect – a weak immune system is strengthened, while partial immune overreactions, such as allergies or autoimmune diseases, are downregulated. An epidemiological study in a clinic in Spain found a significant relevance between vitamin D levels and COVID progression in connection with COVID-19, among other things. Patients admitted to hospital due to COVID-19 received vitamin D, while the control group did not. Both groups received the known standard therapy for COVID-19. With vitamin D, 2% (vs. 50%) of patients required intensive care and 0% (vs. 15%) died. Such a study indicates a statistical correlation.
A recent meta-analysis describes that people with low vitamin D levels (10-20 nmol/l) get around 86% more infections than people with a good vitamin D supply (60-90 nmol/l), which is particularly true for the low baseline values (< 25 nmol/l), which, according to the RKI study, half of the population is at in winter, showing the potential that would exist here, for example through preventive administration, but which is currently not being exploited.
Status Determination
In order to carry out the above-mentioned studies, the vitamin D status must first be determined. This is determined in the laboratory using blood samples.
More precisely, it is determined by measuring 25-hydroxyvitamin D, or 25(OH)D for short, in the blood serum. 25(OH)D is a precursor of active vitamin D and can be expressed in units of nmol/l or ng/ml (to convert nmol/l to ng/ml, divide the value by 2.5).
Various reference values can be used to assess 25(OH)D serum levels. The Robert Koch Institute uses the internationally frequently used classification of the US Institute of Medicine (IOM), which relates to bone health and classifies 25(OH)D serum values as follows:
Recommendations and Supplementation
A meta-analysis of vitamin D supplementation, which examined the relationship between vitamin D and infections, found that the vitamin D groups had an average of 12% fewer infections. However, it is not only the administration of vitamin D itself that is decisive here, but also the supplementation interval. The study shows that a daily dose of 400-2,000 IU resulted in a 19 % reduction in infections compared to rarely administered high doses with 3 % fewer infections. Daily doses are therefore more efficient for the immune system than the same dose administered infrequently as a bolus.
Some laboratories are therefore now setting a lower limit of 75 nmol/l (instead of the previous 30 nmol/l) and many vitamin D protagonists are calling for an optimum value of over 100 nmol/l. Under today’s living and nutritional conditions, practically no-one achieves the latter (unless they are being substituted).
The German Nutrition Society (DGE) recommends supplementing vitamin D if the body’s own production of the vitamin is not possible – which is the case in Central Europe during the winter months, but also, for example, for people who are bedridden and unable to leave the house. In general, older people are considered a particular risk group for a vitamin D deficiency, as the immune system steadily loses efficiency with age. In addition, the skin’s ability to produce vitamin D decreases.
The DGE recommends taking 800 international units (IU) of vitamin D per day. However, doses higher than this should only be taken if the vitamin D levels have been tested by a doctor beforehand and are correspondingly too low. There is a risk of overdosing, which in the worst case can lead to kidney damage.
However, if a deficiency has been identified, the American Society of Endocrinology recommends as much as 1,500 to 2,000 IU per day to bring vitamin D levels back above 30 ng/ml.
If the vitamin intake is be-low the recommended daily dose, the body’s buffer stores are emptied first. As soon as these are used up (this usually takes around four to twelve weeks, de-pending on how full they were at the beginning), there is a risk of possible deficiency symptoms as among other things:
- bone softening and skeletal deformation
- rickets (in infants and children)
- osteomalacia (in adults)
- decrease in bone density (osteoporosis)
- susceptibility to infections
- mood swings
- depression
- …
Sources
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