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Vitamin D: How to make sure you have enough in winter!

Vitamin D not only ensures strong bones, but is also said to make it easier to lose weight and protect against diseases such as cancer and Alzheimer's. When it comes to increasing physical performance with micronutrients, very few athletes think of vitamin D. Thanks to a recent study, however, the sunshine vitamin is shining in a new light. Previously associated with strong bones, it has now almost earned the title of "fitness supplement".

The sun vitamin and its function in the body

Few vitamins get as much attention as the sun vitamin. Strictly speaking, it is not really a vitamin at all, as the body can also produce it itself (endogenous synthesis). Vitamin D3 (cholecalciferol) is formed in the skin from the precursor 7-dehydrocholesterol. Prerequisite: sufficient sunlight - more precisely UV-B radiation - reaches the skin.

The term is used to summarise a range of different compounds. Vitamin D3 (cholecalciferol) is the most important of these and is mainly found in animal foods. In contrast, the less effective D2 (ergocalciferol) is found in plants. Vitamin D3 is further converted into the active form, the hormone calcitriol, in our body. This plays an important role in the calcium and phosphate balance. For example, it is involved in the transport of calcium from the intestine and the hardening and mineralisation of bones. A deficiency is therefore also reflected in lower calcium levels. Bone softening (osteomalacia) and bone deformation (rickets) are typical consequences. Around the turn of the century in particular, many children suffered from rickets. Due to the industrial revolution, some of them had to work up to twelve hours a day in mines. In winter, on the other hand, children did not see daylight for days on end. Today, babies are therefore given the sun vitamin from the second week onwards to prevent rickets.

For a long time, the importance of the sun vitamin was limited to its role in bone health. However, in recent years, low vitamin D levels have been linked to an ever-growing list of diseases. For example, it is said to promote the development of osteoporosis, heart attacks, diabetes, cancer, dementia, high blood pressure, depression, multiple sclerosis, Alzheimer's or Parkinson's.


Does the body also produce vitamin D in winter?

From around mid-October to mid-March, the body is unable to produce the vitamin as the sun's rays are no longer intense enough. So even if we sit out in the sun in a T-shirt and shorts, our skin would not be able to synthesise it in winter. Unfortunately, our diet offers no substitute and is not suitable for covering our vitamin D requirements. Significant amounts can be found in mushrooms or oily sea fish, for example. However, you would have to eat large quantities of these every day to cover your requirements. However, studies by the Robert Koch Institute show that the majority of Germans are not optimally supplied with vitamin D.

Taking supplements is simpler and less complicated. From the age of 65 at the latest, the body's own synthesis via the skin is no longer sufficient to cover the vitamin requirement, even in summer. The synthesis capacity of the skin decreases significantly with increasing age. This age group should therefore take sun vitamin supplements all year round.

One tablet of sun vitamin from Nutri-Plus provides you with 25 µg of vitamin D in combination with vitamin K per day. It is purely plant-based and is obtained from lichen.

Why are many vitamin D supplements not vegan?

Many manufacturers of food supplements obtain their vitamin D3 from animal-based raw materials. Most frequently, lanolin - also known as wool wax or wool fat - is used. However, vitamin D3 can now also be produced vegan. The D3 in our sun vitamin is obtained from lichen, for example.

Good to know: For food supplements, the amount of vitamin D is stated in international units (IU = international unit). One IU corresponds to 0.025 µg of vitamin D3. One 1 µg is 40 IU. The German Nutrition Society (DGE) currently recommends a daily intake of 20 µg for adults.

New study shows: vitamin D improves performance

When it comes to increasing physical performance with micronutrients, very few athletes think of vitamin D. Thanks to a recent study, however, the sun vitamin is shining in a new light. While it was previously associated with strong bones, it has now almost earned the title "fitness supplement".

In a recently published study, A. Marawan et al. from Virginia Commonwealth University (VCU) investigated the relationship between vitamin D levels and cardiorespiratory fitness (CRF) in adults. The term cardiorespiratory relates to the heart and respiration. It describes the ability of the heart and lungs to supply the muscles with oxygen during exercise. In this context, the term aerobic endurance is often used. It is determined by measuring the maximal oxygen consumption (VO2 max) during training. Higher cardiorespiratory fitness not only ensures better athletic performance, but also protects against chronic diseases.

Vitamin D and cardiorespiratory fitness

The research was based on data from the American Nation Health and Nutrition Survey. They analysed 1,995 adults aged 20-49 years. The US researchers compared the maximum oxygen consumption VO2 max (as an indicator of CRF) with the vitamin D levels in the blood.

The result:

People with high vitamin D levels had a significantly higher CRF than participants with low levels. Even when so-called confounding factors such as weight, age, gender, high blood pressure and smoking were included in the analysis, a clear correlation between vitamin D levels and cardiorespiratory fitness was evident.

In addition, it was shown that every 10 nmol/l increase in vitamin D levels in the blood led to a 0.78 ml/kg/min increase in VO2 max. This means that there is a so-called dose-response relationship and that every increase in vitamin D is associated with an increase in performance.

The researchers now want to conduct clinical studies to find out exactly how vitamin D supplementation affects physical performance and what amounts are optimal.


Dr Amr Marawan, head of the study, summarises the results: "Our study shows that a higher vitamin D level is associated with better performance. We also know from previous research that vitamin D has positive effects on the heart and bones. Make sure your vitamin D level is normal to high."