Vitamin D3, also known as cholecalciferol, is essential for bone health, the immune system and muscle function. It is produced in the skin by sunlight, but can also be obtained through food or supplements. But why is vitamin D3 so important and how can you ensure an optimal supply?

What is vitamin D3 and what function does it have?

Vitamin D3 is a fat-soluble form of vitamin that is synthesized by exposure to sunlight on the skin. There are two main forms of vitamin D:

• Vitamin D2 (ergocalciferol), which comes from plants and fungi

• Vitamin D3 (cholecalciferol), which is found in animal sources and is better utilized by the body

After absorption, vitamin D3 is converted in the liver into the storage form 25(OH)D (calcidiol). In the kidneys it is further processed into the active form 1,25(OH)2D (calcitriol), which regulates numerous processes in the body, in particular calcium and phosphate metabolism.

The most important functions of vitamin D3

• Bone health: Supports calcium absorption from food and contributes to bone density

• Immune system: Promotes the immune system and can counteract inflammatory diseases

• Muscle function: Influences muscle strength and reduces the risk of falls and injuries

• Cardiovascular health: May reduce the risk of high blood pressure and heart disease

• Mental health: Associated with lower likelihood of depression and anxiety

• Metabolism and insulin sensitivity: May help regulate blood sugar levels and reduce the risk of type 2 diabetes

vitamin D3 sources

sunlight

The most effective way to produce vitamin D3 is through sun exposure. In the summer months, 15 to 30 minutes of sun exposure on the face, arms and legs is enough. Various factors influence the body's own production:

• Season and latitude: In winter, UV radiation is not sufficient in many regions

• Skin type: Lighter skin produces more vitamin D than darker skin

• Sunscreen: High sun protection factors almost completely block vitamin D synthesis

• Age: As we age, the body’s own production decreases

Foods with Vitamin D3

Only a few foods contain significant amounts of vitamin D3. The best sources include:

• Fatty fish such as salmon, mackerel and herring

• egg yolk

• Dairy products and fortified foods

• mushrooms (especially vitamin D2)

• cod liver oil

dietary supplements

Since many people do not absorb enough vitamin D3 through sun and diet, especially in the winter months, supplementation can be useful. The German Nutrition Society (DGE) recommends:

• Adults: 800 to 1000 IU per day

• Children and adolescents: 400 to 800 IU per day

• Seniors or people with a proven deficiency: up to 4000 IU per day (under medical supervision)

Vitamin D3 deficiency: causes and symptoms

A deficiency in vitamin D3 is widespread, especially in regions with little sunlight. Possible causes are:

• Little sun exposure, for example due to long stays indoors or the winter months

• Darker skin types, as melanin inhibits vitamin D production

• Insufficient dietary intake

• Increased need, for example during pregnancy or breastfeeding

• diseases such as liver and kidney failure

Typical symptoms of a deficiency are:

• muscle weakness and pain

• bone pain and osteoporosis

• Increased susceptibility to infection

• tiredness and exhaustion

• Depressive moods

Benefits of Vitamin D3 Supplementation

An adequate supply of cholecalciferol can:

• Preventing bone loss and fractures

• Strengthening the immune system

• Reduce the risk of chronic diseases

• Improve muscle function

• Supporting mental health

Conclusion

Vitamin D3 plays a central role in numerous processes in the body. A sufficient supply through sunlight, diet or nutritional supplements is crucial to staying healthy and productive in the long term. Targeted supplementation can be particularly useful in the winter months to prevent a deficiency and promote general well-being.

Sources

1st Holick, M.F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357 (3), 266-281.

2nd Bouillon, R. (2017). Vitamin D and human health: from the gamete to the grave. Journal of Steroid Biochemistry and Molecular Biology, 173 , 1-3.

3. Pludowski, P., et al. (2018). Vitamin D supplementation guidelines. Journal of Steroid Biochemistry and Molecular Biology, 175 , 125-135.

4th Grant, W.B., et al. (2020). Evidence that vitamin D supplementation could reduce the risk of influenza and COVID-19 infections and deaths. Nutrients, 12 (4), 988.

5th Bischoff-Ferrari, HA, et al. (2012). A pooled analysis of vitamin D dose requirements for fracture prevention. New England Journal of Medicine, 367 (1), 40-49.

6th Autier, P., et al. (2014). Vitamin D status and ill health: a systematic review. The Lancet Diabetes & Endocrinology, 2 (1), 76-89.

7th Sizar, O., et al. (2022). Vitamin D deficiency. StatPearls Publishing.