Vitamin D is actually not a vitamin but a fat-soluble (pro)hormone. It is made of the “good” kind of cholesterol which is, at the same time, the main component in the production of many other important hormones (estrogen, progesterone, testosterone, DHEA etc). This is one more reason why it is very important to eat enough good quality fats in winter.

Vitamin D is involved in more than 200 processes in our body

The most obvious role of vitamin D is maintaining balance of calcium and phosphate in blood, which is important for the mineralisation of bones and teeth. However, vitamin D is also involved in more than 200 other processes in our body. It is important in prevention of cardiovascular diseases, dementia and other neurological states, it relieves the symptoms of depression and plays a great role in the function of the immune system. It affects the course of many autoimmune diseases such as type 1 diabetes, rheumatological diseases and multiple sclerosis.

With Covid-19, the role of vitamin d in the immune system became more apparent. Research shows that efficient levels of vitamin D reduce the risk of acute respiratory infections and positively influence the course of the disease.

The ideal levels of vitamin D in healthy adults are 30-50 ng/ml. We talk about vitamin D deficiency in levels under 20 ng/ml, and about severe deficiency when the levels drop under 12 ng/ml. Levels above 50 ng/ml can have a negative effect on the body, mainly connected to excess calcium which can cause heart arrhythmias or a kidney disease.

Research shows vitamin D deficiency in over  80% of people throughout the whole year

The main source of vitamin D are UVB sun rays, which convert the inactive form of vitamin B into an active form in our skin. This source depends greatly on many different factors like seasons, length of the day, presence of clouds in the sky, the quality of the air,  the amount of melanin in the skin and use of sunscreen. Sunscreens with UVB factor higher than 8 prevent the formation of vitamin D in the skin, but on the other hand also help prevent some serious skin diseases. Research shows vitamin D deficiency in over  80% of people in middle Europe throughout the whole year.

Ideal daily dose for healthy adults is 800 - 2000 IU of a vitamin D supplement

Because of its very important role  in the body, it is necessary (or at least recommended) to supplement vitamin D. The opinions about the ideal daily dose are different and vary between 800 – 2000 IU of a vitamin D supplement for healthy adults. This is also a dose that I recommend to all adults, especially in winter time, even if you don’t know your exact levels (exceptions are people who are prone to calcination and people with some rare conditions like hyperparathyroidism, sarcoidosis and kidney stones).

Throughout the years of my work with patients I met many people with severe vitamin D deficiency (values under 12 ng/ml). In such cases it is recommended to take significantly higher doses of vitamin D for the first couple of months to recover the reserves. However, this is not something that I would recommend to anybody. If you wish to know your exact levels, it is best to talk to your doctor and check your blood values.