Currently, vitamin D is perhaps the most fashionable and discussed. In everyday life, it has long been part of a “healthy lifestyle”, and in the scientific world, the relationship of this vitamin has been studied with almost all diseases.
Vitamin D belongs to fat-soluble vitamins, it is stored in fat cells and liver cells. This feature allows the body to accumulate vitamin and gradually extract it as needed.
The history of the “solar” vitamin dates back to 1914, when it was first noticed that dogs who received food with the addition of fish oil did not suffer from rickets. However, initially this effect was associated with vitamin A, which was part of fish oil. However, in 1922 it was proved that the development of rickets was prevented by a completely different, previously unknown vitamin, which later became known as vitamin D.
What is vitamin D needed for?
For many years after the discovery of vitamin D, the belief persisted that it was needed solely for the strength of the skeleton. Scientists have found that it increases the absorption of calcium from the intestine, and calcium is the main building material for bones. However, as the study of this vitamin began to appear more and more information about its active participation in the work of the most important systems of the body – cardiovascular and immune. In addition, vitamin D is an important component in carbohydrate metabolism, necessary for the thyroid gland to function, which has caused such great interest in it.
How do we get vitamin D?
Vitamin D is unique. This is the only vitamin that can be formed in the skin under the influence of ultraviolet rays. Therefore, it is often called “sunny”. But how much vitamin is produced in the skin depends on its color – the darker it is, the less vitamin D is formed. This is due to the higher content of melanin in dark skin – the pigment that determines its color.
Another source of vitamin D is food. These are fatty varieties of fish, dairy products (milk, butter, sour cream, cheese), egg yolks, some types of mushrooms, beef liver. The record holder in vitamin D content is herring – 100 g of this fish can contain up to 1,676 IU of vitamin per 100 g, a little less – wild salmon, 100 g of this product contains from 600 to 1000 IU – this is the daily norm of vitamin. Four times less contains farmed salmon. The intermediate position between them is occupied by herring, canned sardines, mackerel and tuna.
Unfortunately, we can only get about 20% of vitamin D from food, and the remaining 80% still come from our own production in the skin.
What is the difference between vitamins D, D2 and D3?
We get vitamin D in an inactive form – in the form of vitamin D3, which comes from food, and is also formed in the skin under the influence of ultraviolet radiation, and in the form of vitamin D2, which comes only from food. Both of these forms are equivalent to each other and together make up vitamin D (D2 + D3 = D). In fact, these forms of vitamin are precursors of vitamin D. Therefore, before starting its action, the vitamin must be activated, that is, change its chemical structure. This happens in the liver and kidneys. Initially, the inactive vitamin enters the liver, turning into 25 (OH) vitamin D – an intermediate form. Further, it enters the kidneys from the liver, being converted to 1,25 (OH)2 vitamin D – the active form of vitamin. It is in this form that vitamin D begins its action in various tissues and organs.
Vitamin D deficiency
The benefits of vitamin D have been discussed for more than a year. Therefore, adherents of a healthy lifestyle try to do everything to prevent deficiency, enriching their diet with foods high in vitamin D and spending a considerable amount of time in the sun. However, this is not a guarantee that the body will be saturated with a sufficient amount of vitamin. And the proof of this is the African countries in which everything is fine with ultraviolet light and, nevertheless, about 15% of the inhabitants suffer from a deficiency of this vitamin.
And, given the northern location of most regions of our country, the peculiarities of nutrition, as well as the widespread prevalence of diseases that reduce the effectiveness of the intake or activation of vitamin D, it can be assumed that in Russia most of the inhabitants suffer from a deficiency of this vitamin.
The effect of vitamin D deficiency on the body
Despite a large number of studies on vitamin D deficiency, its effect on some systems and organs is still controversial and requires further study.
At the same time, the negative effect of reduced vitamin levels on the immune system has been proven. As the coronavirus pandemic has shown, people with severe vitamin D deficiency were much more likely and more seriously ill with coronavirus.
The relationship of vitamin D deficiency with oncological diseases has also been proven. In pregnant women, vitamin deficiency causes fetal growth retardation or deformity of its bones. And in adults, it provokes osteoporosis, increasing the risk of fractures.
What provokes vitamin D deficiency?
- Dark skin. As mentioned earlier, the main source of vitamin D is the skin. But the amount of vitamin produced depends on its color – the darker the skin, the less vitamin D is formed. This is due to the higher content of melanin in dark skin – the pigment that determines its color. Melanin reduces the production of vitamin D by limiting the intake of ultraviolet light into the skin. Therefore, the more we sunbathe, the less vitamin is produced! In this way, the body prevents excessive vitamin formation during prolonged exposure to the sun. But this is a good defense mechanism in the southern regions, and in the northern regions, owners of dark skin experience a more pronounced vitamin D deficiency compared to light-skinned people.
- Sunscreen. The lighter the skin, the more it is exposed to the harmful effects of sunlight and exposure to the sun can lead to burns, skin cancer. Therefore, in order to prevent this, it is necessary to apply sunscreen before tanning. But, just like melanin, it prevents the penetration of ultraviolet light into the skin, and this leads to less vitamin D production.
- The presence of liver diseases such as non-alcoholic fatty liver disease, alcoholic steatohepatitis, cirrhosis of the liver or chronic kidney diseases, for example, chronic pyelonephritis or chronic glomerulonephritis, can cause insufficient activation of vitamin in these organs
- Inflammatory bowel diseases or lactase deficiency – disrupt the absorption of vitamin D from the intestine.
- Obesity leads to reduced vitamin D levels. This is due to the ability of fat cells to store vitamin D in large quantities. But the process of vitamin return in obesity is disrupted. Therefore, a paradoxical situation arises – it seems that the body has a large supply of vitamin, but it cannot get it back.
- Medications – long–term use of antifungal, antiepileptic drugs, as well as glucocorticoid hormones, vitamin deficiency method – can provoke vitamin D deficiency.
Symptoms of vitamin D deficiency
Unfortunately, it is very difficult to feel vitamin D deficiency, since there are very few symptoms, and they are not present at all. These include:
- muscle weakness;
- unpleasant sensations in the bones.
But even here it is necessary to make a reservation – similar symptoms can occur in many other conditions. Therefore, even if they appear, in most cases they are not associated with an insufficient amount of vitamin D.
Excess vitamin D
Before talking about an overdose of vitamin D, I would like to clarify that getting vitamin naturally (through nutrition and exposure to ultraviolet light) never leads to an excess amount of it!
But uncontrolled intake of vitamin D preparations, especially its active form (calcitriol and its derivative alfacalcidol), can provoke hypervitaminosis.
As for the manifestations of an excessive amount of vitamin D, it also has its own characteristics – all the symptoms of overdose are not associated with an increased level of the vitamin itself, but with its excessive effect, i.e. increased absorption of calcium from the intestine and increased blood intake (hypercalcemia). It is the high level of calcium in the blood that has a toxic effect on the body. First of all, this affects the emotional state, which can be very different – from the development of apathy, depression, to increased irritability and excitement. The gastrointestinal tract is also affected: abdominal pains begin to bother, nausea and constipation appear. Later, stomach ulcer develops, as well as inflammation in the pancreas – pancreatitis. In severe cases, a coma may develop.
The problem of overdose of fat-soluble vitamin D is aggravated by the fact that it is able to accumulate in the body, however, like all other fat-soluble vitamins, so it becomes almost impossible to quickly get rid of its excess amount.
How to determine the level of vitamin D?
Currently, the level of vitamin D in the body is assessed by a blood test. There are no other ways to determine the vitamin yet. For evaluation, it is better to choose – 25 (OH) vitamin D – the form that is formed in the liver. However, if you have serious kidney diseases, or for some reason the absorption of vitamin D preparations (colecalciferol and ergocalciferol) does not occur, then it is necessary to additionally investigate the active form of vitamin – 1,25 (OH)2D. This form will show whether the vitamin is activated in the kidneys or not. In other cases, it does not make sense to investigate the active form, since it does not reflect the reserves of vitamin D in our body.
The “normal” level of vitamin D is considered to be in the range of 30 ng/ml (or 75 mmol/l) to 100 ng/ml (250 mmol/l). If the level drops below 30, but not below 20 mg / ml, this is regarded as a “deficiency” of vitamin. A level below 20 ng/ml is taken as a “deficient” condition. An increase of more than 100 ng /ml indicates an “excessive” amount of vitamin D. And if the level exceeds more than 150 ng / ml, a toxic effect on the body occurs.
How much vitamin D should I take?
If you have never determined the level of vitamin D before and have not taken it in the form of supplements, then, of course, you can start taking a maintenance dose of vitamin D. This is unlikely to harm the body. However, if you have a vitamin deficiency, then a maintenance dose is unlikely to significantly increase the level of vitamin D. And taking higher doses, without a preliminary assessment of the level, can lead to excess content in the body. Therefore, before taking it, it is better to determine the vitamin level in order to understand how much your body needs.
If, according to the results of your study, the level of vitamin D is within the normal range, then you can start taking a maintenance dose. The level from 600 to 2000 IU per day is considered to be supportive. It is better to take the inactive form of the drug (colecalciferol) during or after meals once a day. But, you can also take it once a week, since the activation of the vitamin does not occur immediately, but only when it is necessary for the body. For example, if the daily dose is 1000 IU per day, then you need to take 7,000 IU – once a week. If the vitamin D level is below normal, it is better to consult with a specialist before taking the drug so that he determines the necessary dosage and duration of treatment. This is especially true for people with chronic diseases, as some of them require adjusting the dose of vitamin D.
Summarizing all of the above, it should be noted that the effect of vitamin D on our body is very great. This is confirmed even by the mechanism of its action – it is exactly the same as that of hormones. Therefore, it is often called a “hormone”. And even if we do not always feel a deficiency of this vitamin, a slight decrease in its level can negatively affect the work of our body. However, as well as an overabundance. Therefore, do not forget that in this case the “golden mean” is good!