Vitamin D – What you need to know

The body produces vitamin D itself. Therefore, it is not really a vitamin, but rather a hormone. The most important forms are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

Vitamin D promotes the absorption of calcium and phosphorous in the intestines. It therefore regulates the absorption of minerals and calcium levels in the blood. It also supports the development of muscles, bones and teeth, and strengthens the immune system. Furthermore, vitamin D supports our mental well-being. It regulates the neurotransmitters serotonin, dopamine and noradrenaline. These happiness hormones affect our mood.

Your daily requirement varies depending on age:

• Infants up to age 1: 10 micrograms
• People aged 1 to 60: 15 micrograms
• People over age 60: 20 micrograms

15 micrograms of vitamin D are contained for example in 180 grams of wild salmon, 515 grams of raw chicken eggs (equivalent to approximately nine medium-sized eggs) or 485 grams of fresh porcini.

According to the Federal Office of Public Health (FOPH), someone has a vitamin D deficiency if the 25-hydroxyvitamin D concentration in their blood is less than 50 nanomoles per litre of blood serum. A level below 25 nmol/l is considered a severe deficiency.

Experts disagree on what constitutes a vitamin D deficiency, however, so these figures should be treated with caution. Some experts think that deficiencies are systematically overestimated, as the reference value of 50 nmol/l is only an average across the year. The body can store a certain amount of vitamin D in the summer which can then last through the winter.

There is no conclusive evidence that regularly testing vitamin D levels among the general population is helpful. The FOPH therefore does not recommend general screening as a preventive measure. According to the FOPH, in most cases it is not necessary to measure someone’s vitamin D levels before they take supplements – as long as they do not exceed the recommended daily amount of 600 IU for adults and 800 IU for those aged 60 and over. These recommendations are supported by recognised medical publications. A test is only considered useful for high-risk groups. These include those who are pregnant, newborn babies, older people with osteoporosis or bone fractures and patients with chronic kidney or liver disease.

Vitamin D supplements are available in a variety of forms, from tablets and capsules to drops and fortified foods.

Even if you are not in a high-risk group and don’t have a diagnosed vitamin D deficiency, there is no harm in taking vitamin D supplements if you think you might be deficient. However, you should not exceed the recommended daily amount of 600 IU/15 µg for adults and 800 IU/20 µg for those aged 60 and over. The health benefits of vitamin D supplementation in this context remain debatable. Numerous studies indicate that it has no impact on the risk of suffering cardiovascular disease, cancer, bone fractures or depression.

If you have been diagnosed with a severe vitamin D deficiency, you should discuss taking supplements with your doctor, including how much to take.

Is it possible to take too much vitamin D?

Only the excessive consumption of supplements can cause a spike in vitamin D levels. This results in an excessive concentration of calcium in the blood, which manifests itself in a general feeling of weakness, headache and cardiac arrhythmia. In serious cases, taking too much vitamin D can lead to kidney stones and kidney failure. You should therefore avoid taking multiple vitamin D supplements at the same time.