Vitamin D is a group of biologically active substances that are formed under the action of ultraviolet rays in the skin and entered the human body with food.

The action of vitamin D:

– ensures normal growth and development of bones, prevents the development of rickets and osteoporosis, by regulating mineral metabolism;

– It promotes muscle tone, enhances immunity, is essential for the functioning of the thyroid gland and normal blood clotting;

– helps the body to restore the protective sheath surrounding the nerves;

– participates in the regulation of blood pressure and heart rate;

– Prevents the growth of cancer cells.

Research is in full swing on the effects of vitamin D on:

– senile dementia and Alzheimer’s disease;

– Cognitive function (thinking disorders), especially in aging individuals;

– Mood disorders, especially depression in older adults;

– Autoimmune diseases, such as psoriasis.

Sources of vitamin D

Provided the body receives sufficient ultraviolet radiation, the need for vitamin D is fully compensated. However, the amount of vitamin D synthesized by sunlight depends on factors such as: 

– wavelength of light (the mid-wavelength spectrum we get most effectively in the morning and at sunset;

– baseline skin pigmentation and (the darker the skin, the less vitamin D is produced by sunlight)

– age (aging skin loses its ability to synthesize vitamin D);

– level of air pollution (industrial emissions and dust do not pass the spectrum of ultraviolet rays that potentiate the synthesis of vitamin D, this explains, in particular, the high incidence of rickets in children living in Africa and Asia in industrial cities).

The need for vitamin D is compensated by vitamin D3 (cholecalciferol), which is formed in the skin from provitamins under UV rays of sunlight. Provitamins come partly in the body in a prepared form from plants, and partly are formed in the tissues of their cholesterol. 

Additional food sources of vitamin D are dairy products, fish oil, fish liver, caviar, egg yolk. In practice, however, milk and dairy products do not always contain vitamin D, or contain only trace amounts (for example, 100 grams of cow’s milk contain only 0.05 mg of vitamin D), so their consumption, unfortunately, cannot guarantee that our need for this vitamin is covered. 

Oatmeal, potatoes, parsley, and some herbs such as alfalfa, dandelion greens, nettles, and horsetail also contain vitamin D in small amounts.

Daily vitamin D requirement

The monthly requirement for vitamin D 20000 or more  Increased need for vitamin D contributes to a lack of ultraviolet radiation, naturally dark skin, older age, vegetarianism and following a low-fat diet, digestive disorders, pregnancy and lactation, period of intense growth and development. These people need additional vitamin D supplementation.

When treated with high doses of vitamin D drugs is recommended to simultaneously prescribe vitamin A (retinol), as well as ascorbic acid (vitamin C) and B vitamins.

I heard on TV about the benefits of vitamin D, and decided to buy it at the pharmacy. But I was confused, because there it is both in oil and in aqueous solution, and its forms are different: D2 and D3. Which one is the best to choose? And how do I know whether I have a deficit of this substance or not, so that I don’t waste my money?

There are several variants of natural vitamin D. They differ in chemical structure. D 2 (ergocalciferol) is a plant-based vitamin, and D3 (cholecalciferol) comes from animal products. However, when ingested, all forms of provitamin D are converted into a universal form: 25 – OH vitamin D.

This form is stable, circulates long enough in the blood and reflects all the metabolic transform autoimmune of vitamin D in the body, so it is considered the main marker by which to judge whether a person has enough or not of this substance. 

In addition, a blood test for 25-OH vitamin D will help calculate the optimal dose of the drug, an overdose of which can be dangerous. In some cases, it is also necessary to assess the balance of different metabolic variants of substances of the vitamin D group – to do a comprehensive test for vitamin D.

For this there are separate laboratory tests. But it makes sense to do them only at the request of a doctor. For example, patients with chronic kidney disease usually have reduced synthesis of the active metabolite of vitamin D – 1,25 (OH)2 D.

Is it necessary to take a blood test for vitamin D on an empty stomach? And in what cases is this test done?

The test for total vitamin D (25-OH vitamin D) is necessary for those who have signs of deficiency of this substance. Such symptoms are many and very diverse: asthenia, depression, nervousness, irritability, increased sweating at the back of the neck and hair loss, sleep disorders, coordination problems.

But most often the reasons for the study are complaints of muscle weakness, brittle bones and frequent fractures, especially alarming if blood tests record a decrease in calcium levels.

Examine the content of vitamin D makes sense also for people with diseases of the intestine and gallbladder, because vitamin D is fat-soluble and normally must be absorbed in the intestine with fats, which are not absorbed if the digestive tract is not healthy.


Also, vitamin D levels should be checked periodically for those who regularly take certain medications (such as anticonvulsants and glucocorticoids), which can increase the need for vitamin D.

You can be tested no earlier than 3 hours after a meal or in the morning on an empty stomach, excluding the intake of drugs and supplements containing vitamin D for 3-4 days before the blood test. You can drink clean water. In 1 to 2 days, the test will be ready.