From a biological perspective, vitamin D, often referred to as the "sunshine vitamin," is not a classic vitamin, but rather a prohormone that our body synthesizes from cholesterol with the help of UV radiation. It is essential for our health: in addition to its well-known role in bone density and the prevention of osteoporosis, its genetic role is increasingly coming into focus. Current studies suggest that optimal vitamin D levels can protect our DNA from oxidative degradation.
How vitamin D protects DNA and slows down the biological clock
Telomeres are a key marker of biological age. They can be thought of as protective caps at the end of shoelaces: they prevent our DNA from fraying or becoming damaged.
- – The aging process: With each cell division, these protective caps become a little shorter. If they become too short, the cell can no longer regenerate.
- – The role of vitamin D: Recent studies suggest that optimal vitamin D levels can slow down this process. It acts as a protective shield against oxidative stress and helps to keep telomeres stable.
A stable vitamin D level could therefore serve as a "buffer" for the biological clock and slow down the cellular aging process.
Vitamin D deficiency: symptoms and far-reaching consequences
A severe deficiency causes bone tissue to become demineralized and soft. In children, this leads to rickets with growth disorders, dental development disorders, and bow legs. In adults, the clinical picture is osteomalacia with severe muscle and joint pain and bone fractures. Historically, vitamin D deficiency and rickets were widespread in the low-light industrial cities of Northern Europe. Malnutrition, reduced UV radiation in winter, clothing norms that covered large areas of skin, and long working hours (for children) all played a role. Today, these conditions are rare thanks to improved healthcare and nutrition.
Influence on the immune system and skin appearance
Vitamin D modulates our immune system. Studies associate low levels with:
- – Autoimmune diseases and infections.
- – mental illnesses (such as seasonal affective disorder).
- – Inflammatory skin conditions: Low levels are often measured in cases of acne, rosacea, neurodermatitis, and psoriasis.
- – Hair loss: Vitamin D is involved in the anagen phase (growth phase) of hair follicles.
However, it is not clear whether the reduced vitamin D levels are a consequence of the disease, for example as a result of increased consumption, or whether they are caused by a disease-related change in lifestyle with less exposure to sunlight. Blood levels were particularly low in overweight patients: since vitamin D is fat-soluble, it becomes "trapped" in fatty tissue, which reduces its bioavailability in the blood.
Recording or in-house production? The path of Vitamin D
There are two ways to fill the stores: through nutrition and UV-dependent synthesis in the skin.
1. Get vitamin D through your diet
Very few foods are rich in vitamin D.
These include:
- – Fatty fish (herring, salmon, mackerel)
- – Eggs and (fermented) dairy products
- – Mushrooms (these produce vitamin D when exposed to sunlight, similar to humans)
The fact is: on average, only 10-20% of our requirements can be met through food.
2. The body's own synthesis through UVB radiation
Most vitamin D is produced by the skin, liver, and kidneys. Without sunlight, vitamin D cannot be produced in our bodies.
This is where the "winter dilemma" lies: in northern latitudes (above the 35th parallel), the intensity of UVB radiation from October to March is not sufficient to stimulate production—no matter how long you go for a walk.
At the same time, we need to protect our skin. While UVA radiation (present all year round) is responsible for skin aging and wrinkles by damaging collagen and elastin fibers, too much UVB radiation causes sunburn and DNA damage (such as pigment spots and actinic keratoses).
Limited exposure to sunlight improves the stressful symptoms of inflammatory skin conditions such as psoriasis and neurodermatitis. It is believed that low-dose UVB radiation has an anti-inflammatory effect, strengthens the skin barrier, improves wound healing, and even offers antioxidant protection and protection against DNA damage. Vitamin D appears to have a regulating effect on the formation and maturation of keratinocytes. These are the structure-forming cells of the upper skin layer. An irregular structure of the uppermost skin layer plays a role in acne and skin barrier disorders. In children and adults with atopic dermatitis, vitamin D supplementation has been shown to reduce the severity of the disease.
In summary, this means:
We need the sun, but too much is definitely harmful.
Recommendation for summer: For Central European Fitzpatrick phototype II (= fair skin with slight tanning potential), about 10-20 minutes (face, arms, hands) 2-3 times a week is sufficient. Important: Do not risk reddening!
Supplementation: What really matters
When there is not enough sun, supplements can help. The German Nutrition Society (DGE) recommends that adultstake a vitamin D supplement containing 800 IU (20 µg) daily if they are not producing it themselves. It is possible to have your blood levels tested, but this is not yet routinely recommended. In a random sample taken by the Robert Koch Institute, 56% of adults in Germany were found to have suboptimal to deficient levels. However, the threshold values that define an adequate supply vary internationally. Since humans have a high degree of genetic diversity, there also seem to be individual differences in what constitutes "normal" vitamin D levels. For some people, a lower baseline may be their personal normal. At least one meta-analysis showed that low vitamin D levels in the presence of genetic variation did not mean an increased risk of coronary heart disease, stroke, or increased mortality.
Bioavailability & synergies – K2 and magnesium
When taking dietary supplements, there are a few things to keep in mind. In order for vitamin D to work optimally in the body, it needs support:
- – Combination with vitamin K2: Vitamin D promotes calcium absorption. K2 (MK-7) is needed to ensure that this calcium is incorporated into the bones and does not calcify the arteries.
- – Magnesium as an activator: Without magnesium, stored vitamin D cannot be converted into its active hormone form. A magnesium deficiency can therefore prevent vitamin D levels from rising despite intake.
- – Bioavailability: Since vitamin D is fat-soluble, it should always be taken with a meal containing fat (e.g., with avocado, nuts, or high-quality oil). Oil-based drops are often more bioavailable than dry tablets.
- – Dosage: International recommendations vary between 400 and 800 IU per day.
Between longevity trends and genuine health: risks associated with optimizing the biological clock
Our bodies are not machines. More input does not automatically mean that you can achieve improvement. When it comes to nutrition in particular, new findings are constantly emerging and previous recommendations are proving to be outdated or even wrong. Large scientific studies with high case numbers over as long a period as possible are still the most reliable.
In a society that is geared towards high performance and longevity, many people tend to overdose. However, anyone taking vitamin D supplements should be aware that scientific knowledge is constantly evolving.
The trap of self-optimization
The desire to keep your body fit and healthy into old age, while feeling attractive and comfortable, is perfectly healthy. But this drive can also lead you astray:
- – Unrealistic ideals: When our actions are dominated solely by thoughts of performance and idealized self-images.
- – Narcissistic society & social media: Beauty and wellness influencers constantly hold up new trends as a mirror to us. It is tempting to blindly trust these advertising figures.
- – Industry interests: An entire industry benefits from the hype surrounding dietary supplements, where consumption often takes precedence over individual health.
From a medical perspective, it makes sense to obtain balanced information. The recommendations of independent professional associations are a reliable guide in this regard.
Lessons learned from beta-carotene and vitamin E
Scientific studies urge caution with isolated high doses. Historical studies (e.g., the CARET study) have shown that high-dose beta-carotene supplementation paradoxically increased the risk of lung cancer in smokers. Negative effects on heart health have also been observed with high doses of vitamin E.
"The more, the better" does not apply to fat-soluble vitamins.
All fat-soluble vitamins (E, D, K, A) also carry a risk of overdose, as they are stored in the body. This is particularly true when taken in high doses as dietary supplements. With a balanced diet, it is not normally possible to overdose on vitamin D. One exception would be the consumption of foods artificially enriched with vitamin D. Clear labeling is necessary in this case.
In recent years, there have been repeated recommendations on the internet and social media to take high doses of vitamin D supplements, with 4,000 IU per day or more. Among other things, there have been claims that this could protect against COVID-19. In fact, however, this only increases the risk of developing poisoning with serious complications such as hypercalcemia with muscle weakness, cardiac arrhythmia, and kidney failure.
Conclusion: Vitamin D is essential for health and may even slow down the aging process. The winter months in particular can be used for moderate supplementation, but it is advisable to consult a doctor first.
Disclaimer: The information provided in this article is for general information and educational purposes only. It does not constitute medical advice, diagnosis, or treatment and cannot replace consultation with a doctor. Taking high doses of dietary supplements without medical supervision can be risky. The content of this article has been compiled with the utmost care, but no guarantee can be given for the accuracy, timeliness, and completeness of the information provided.