A good supply of vitamin D is essential for healthy bones and teeth, the functioning of the immune system, and many other bodily functions. Vitamin D deficiency could therefore be a risk factor for the development of numerous diseases.
Learn everything you need to know about the functions of this vital nutrient, how to recognize a deficiency, and how to meet your needs.
What is vitamin D?
Vitamin D is a fat-soluble vitamin and, unlike water-soluble vitamins, can be stored in the body. Storage occurs primarily in fat and muscle tissue, and in the liver.
The body meets its vitamin D needs primarily through its own production under the influence of sunlight. Food provides only a small contribution.
Functions of vitamin D in the body
Vitamin D acts like a hormone in the body. It regulates many processes that are crucial for healthy development and function.
We will introduce you to the most important functions of the sunshine vitamin below.
Healthy bones and teeth
Vitamin D promotes the absorption of calcium and phosphate from the intestines and reduces their excretion via the kidneys. Calcium and phosphate are important building blocks for bones and teeth, and vitamin D ensures a good supply of these substances to the body.
A strong immune system
The sunshine vitamin also plays a key role in regulating the immune response and helping to prevent infections. A good supply during the cold season is therefore especially important.
Improved muscle strength
Vitamin D increases muscle strength by, for example, stimulating muscle growth and improving the oxygen supply to the muscles.
Protection against chronic diseases?
Recent studies suggest that vitamin D deficiency may be an important risk factor for the development of chronic diseases such as multiple sclerosis ( 1 ), diabetes ( 2 ), cardiovascular diseases ( 3 ), depression ( 4 ) and even cancer ( 5 ).
Further research is needed to definitively confirm these associations.
How does the body produce vitamin D?
The body can produce the sunshine vitamin itself through a multi-stage process. It uses cholesterol as a starting material.
The process is as follows:
- In the liver, cholesterol is converted into the precursor 7-dehydrocholesterol.
- 7-Dehydrocholesterol reaches the skin, where it is converted into previtamin D3 under the influence of UVB radiation. This previtamin D3 is unstable and spontaneously converts to cholecalciferol (vitamin D3).
- Cholecalciferol is converted into calcidiol in the liver. Calcidiol is the predominant form of the sunshine vitamin in the bloodstream and its storage form. It is also measured in blood tests. Calcidiol is hormonally inactive and is only activated by the body when needed.
- If the body needs active vitamin D (e.g., if calcium levels in the blood are too low), calcidiol is converted into calcitriol, the active form of vitamin D. This activation can occur in any cell of the body.
Foods with vitamin D
Only a few foods contain significant amounts of vitamin D. These are usually foods of animal origin such as fatty fish, organ meat and egg yolk.
Edible mushrooms that have been exposed to the sun before consumption (e.g., sun-dried mushrooms) are particularly suitable as a vegetarian source of vitamin D. Mushrooms contain the precursor ergosterol, which is converted into ergocalciferol (vitamin D2) by UVB radiation. The human body can convert ergocalciferol into active vitamin D3, thus also utilizing non-animal sources of the vitamin.
Vitamin D deficiency is common
The body needs UVB radiation to produce the sunshine vitamin. The amount of UVB radiation that penetrates the atmosphere depends on the position of the sun. At midday, the intensity of UVB radiation, and thus vitamin D production in the skin, is significantly higher than in the morning and evening hours.
However, during the winter months, even at midday, the sun doesn't reach a sufficiently large angle in countries north of the 35th parallel to ensure the body's production of vitamin D. Germany, for example, extends from 47th to 55th degrees north latitude.
To survive the winter without deficiency in Central and Northern European countries, the body's stores of the sunshine vitamin must be replenished by autumn. However, very few people manage to do this.
Studies on the vitamin D status of the population in Germany show that over 60% of adults are not adequately supplied with the vitamin ( 6 ).
To replenish the body's stores, regular outdoor exposure, with sufficient skin exposed to natural sunlight for a sufficient amount of time, is necessary. Our modern lifestyle, with long periods of indoor activity, is therefore not exactly conducive to a good supply of this vitamin.
Symptoms of vitamin D deficiency
Vitamin D is particularly important for the development and maintenance of bones and teeth. A deficiency leads to deterioration of the structure of these tissues, resulting in a loss of strength and resilience. This can lead to diseases such as bone softening (osteomalacia in adults, rickets in children), osteoporosis, and tooth decay.
Since the sunshine vitamin is also important for muscle function, a prolonged deficiency increases the risk of falls and bone fractures in older people.
In addition to these officially recognized symptoms, there are numerous other symptoms and diseases associated with vitamin D deficiency. Reliable scientific evidence is still lacking.
Should I take vitamin D?
Since many factors such as the amount of time spent outdoors each day, skin color, age, geographical location, etc., influence vitamin D levels, the question of whether a dietary supplement should be taken can only be answered after a blood test.
A frequently used international classification assumes a serum calcidiol concentration of at least 50 nmol/L to indicate adequate body supply (6). However, reference ranges can vary depending on the laboratory and are often set higher in orthomolecular medicine.
Depending on the severity of the deficiency, the treating physician or therapist will determine the required dosage. A follow-up should be performed after 2 to 3 months.
Risk of overdose?
An overdose of vitamin D is rare and only occurs when taking supplements at significantly higher doses than recommended. Overdose does not occur naturally, as the body regulates the production of the sunshine vitamin as needed.
An overdose of this vitamin leads to elevated calcium levels in the blood (hypercalcemia). Acute symptoms include nausea, abdominal cramps, confusion, and intense thirst. Chronically elevated calcium levels can contribute to the development of kidney stones and arteriosclerosis.
If you stick to the recommended dosage and check your levels regularly, there is no reason to worry about a possible overdose.
Vitamin D complex from Allvital
Our Vitamin D Complex contains 3000 IU of vitamin D3, which is derived from lichen and is therefore vegan. Due to its high dosage and high bioavailability, this product is ideal for compensating for existing vitamin D deficiency.
Additionally, vitamin C is included in two natural forms, which supports the normal function of the immune system. We've also added the natural sulfur source MSM to the product, which has antioxidant properties and supports the health of skin, hair, and nails.
This results in a balanced preparation that can effectively compensate for a vitamin D deficiency and supports the immune system on various levels.
Vitamin D3 + K2 from Allvital
Vitamin K works synergistically with vitamin D, supporting the absorption of calcium from the blood into the bones and thus counteracting excessively high calcium levels in the blood. It also contributes to normal blood clotting.
Our Vitamin D3 + K2 preparation combines the two vitamins in an oily solution based on coconut oil and olive oil. Each drop contains 500 IU of vitamin D3 and 10 µg of vitamin K2.
This preparation is ideal for individually dosing vitamins and adjusting the dose over the course of use.
Other Allvital products with vitamin D
Other Allvital products containing vitamin D include the combination products Multivitamin Basic , Multivitamin Booster , and Multivitamin Children , as well as the Glucosamine & Chondroitin Complex . These products contain 50 to 200 IU of vitamin D.
Sources
- Carlberg C, Mycko MP. Linking mechanisms of vitamin D signaling with multiple sclerosis. Cells. 2023;12(19):2391. Published 2023 Sep 30.
- Li X, Liu Y, Zheng Y, Wang P, Zhang Y. The Effect of Vitamin D Supplementation on Glycemic Control in Type 2 Diabetes Patients: A Systematic Review and Meta-Analysis. Nutrients. 2018;10(3):375. Published 2018 Mar 19.
- Wimalawansa SJ. Vitamin D and cardiovascular diseases: Causality. J Steroid Biochem Mol Biol. 2018;175:29-43.
- Geng C, Shaikh AS, Han W, Chen D, Guo Y, Jiang P. Vitamin D and depression: mechanisms, determination and application. Asia Pac J Clin Nutr. 2019;28(4):689-694.
- Muñoz A, Grant WB. Vitamin D and Cancer: An Historical Overview of the Epidemiology and Mechanisms. Nutrients. 2022;14(7):1448. Published 2022 Mar 30.
- Rabenberg M, Mensink G. Vitamin D status in Germany. Journal of Health Monitoring. 2016;1(2).
