The role of vitamin D in the body is huge. Its deficiencies are associated with lower immunity, more frequent incidence of inflammatory diseases, heart diseases and even cancer. At the same time, as much as 90 percent. Poles are deficient in vitamin D, and supplementation is the standard recommendation. However, what to supplement? Vitamin D3, D2, or maybe a mixture of both substances? What exactly is vitamin D3? Is Vitamin D3 Different From Vitamin D or D2?

Are vitamin D3 and vitamin D the same?

Vitamin D is not one chemical compound , but a mixture of various substances, mainly vitamins D2 and D3. In the 1930s, the concept of vitamin D1 also functioned, but with time it turned out to be a mixture of D2 and D3.

Nowadays the name "vitamin D1" is not used. It has long been believed that vitamins D2 and D3 affect the body in exactly the same way, which is why it is commonly accepted to treat the name of vitamin D as D3 or D2. Today, however, it is known thatboth substances have a slightly different effect on the body.

To sum up,vitamin D3 is a part of the chemical compounds collectively known as vitamin D . It is not exactly the same, but in Poland vitamin D3 is the most common in dietary supplements. Interestingly, in the United States, the form of vitamin D available as a dietary supplement is vitamin D2.

What is the difference between vitamin D3 and D2?

Vitamin D3 is cholecalciferol , which is formed in the organisms of animals under the influence of UV radiation. Cholecalciferol is produced in two stages. Provitamin D3 is formed from 7-dehydrocholesterol in the skin of animals thanks to the action of UVB radiation with a wavelength of 290-320 nm, which then undergoes thermal isomerization to vitamin D3.

Vitamin D2, i.e. ergocalciferol , is a form found in the organisms of some plants, mainly fungi. It is formed by converting ergosterol under the influence of UV radiation. As a result of exposure to sunlight, humans produce vitamin D3 in the skin.

The structure of vitamins D3 and D2 is not completely different . They only differ in the side chain. There is an additional double bond between atoms in the ergocalciferol moleculecarbon C-22 and C-23 and methyl group C-24. When observing the structural patterns of molecules, it is difficult for a person who is not trained at first sight to notice the difference. Hence, it has long been suggested that both forms of vitamin D are used in the same way by the body.

Vitamins D2 and D3 are prohormones, which means that they are not biologically active. To be used by the human body, they must be transformed into active compounds. In the first stage of enzymatic hydroxylation, vitamins D2 and D3 are converted in the liver to 25-hydroxyvitamin D [25 (OH) D] in the presence of the enzymes 25-hydroxylases. Then, in the kidneys, 1α-hydroxylase converts 25 (OH) D into calcitriol [1.25 (OH) 2D] - an active compound of importance for the human body.

Both vitamin D3 and D2 are eventually transformed into calcitriol. However, scientific reports from recent years show that calcitriol produced from vitamin D2 does not work in the human body in the same way as calcitriol obtained from vitamin D3.

Symptoms of vitamin D deficiency:

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Vitamin D3 is more effective than Vitamin D2

Studies from recent years show that taking vitamin D3 raises blood levels of 25 (OH) D faster and for longer than supplementation with the same doses of vitamin D2. The level of 25 (OH) D is currently considered the best measure of saturation of the body with active vitamin D.

Although the end product of the enzymatic hydroxylation of vitamins D3 and D2 is the same compound - calcitriol - there are likely some slight differences in it that allow cells in the body to distinguish its origin.

The data suggest that these proposed differences between cholecalciferol and ergocalciferol are due to their different affinity for the vitamin D receptor (VDR), which appears to be related to an additional 24-hydroxylation step that inactivates calcitriol. In addition, vitamin D3 is believed to be a potentially preferred substrate for hepatic 25-hydroxylase, which, combined with the possible difference in the rate of 24-hydroxylation, enhances the differences in the effects of vitamins D3 and D2 on the body.

Meta-analysis from 2012 [1] was the first study of this type that compared the effectiveness of taking vitamin D2 and D3 in increasing the concentration of 25 (OH) D in the blood. It clearly showed that supplementation with vitamin D3 is more effective than the same supplementation with vitamin D2. Serum 25 (OH) D levels were 31% to 87% higher with vitamin D3 supplementation than with vitamin D2 at the same doses.

The described effect was achieved regardless of whether it was a long-term supplementation with small doses orone-time intake of shock doses. In addition, serum 25 (OH) D levels are maintained longer as a result of supplementation with vitamin D3. In one study it was observed that after administering 50,000 IU of vitamin D2 and D3 to patients, in those who took vitamin D2, the level of 25 (OH) D dropped sharply after 14 days to baseline values, while in those who received vitamin D3, the concentration of 25 ( OH) D did not return to baseline even after 28 days of observation.

This difference is related to the metabolism of ergocalciferol and cholecalciferol. It turns out that the long-ignored different structure of the side chain of both molecules is probably responsible for significant differences in metabolism and clearly different response of the organism to D3 and D2 supplementation.

This difference in molecular structure directly affects the rate of ergocalciferol conversion to 25 (OH) D in serum, as well as its affinity for the vitamin D binding protein and the VDR receptor, which are key steps in the activation of vitamin D. Ergocalciferol in one of the Metabolism steps into calcitriol are deactivated and therefore cannot be used by the body to the same extent as cholecalciferol. Cholecalciferol (vitamin D3) is the form of vitamin D preferred by the human body.

Vitamin D3 sources

The basic source of vitamin D3 for humans should be skin synthesis under the influence of sunlight. In Poland, however, cutaneous synthesis occurs to a very limited extent. The production of vitamin D in the skin in the geographical area of ​​Poland takes place only from the end of April to the beginning of September, from 10.00 to 15.00, on sunny days. At other times, the amount of sun and the angle of the sun's rays are insufficient.

For this reason, vitamin D3 deficiency is observed in over 90% of Poles. It might seem that the missing amount of vitamin D3 could be provided with the diet. Unfortunately, this ingredient is very rare in food. What is vitamin D3 in?

Vitamin D3 appears in:

  • fish oils,
  • oily sea fish (in 100 g of fresh eel - 1200 IU, fresh wild salmon - 600-1000 IU, and farmed only 100-200 IU, fresh mackerel - 600 IU, fresh rainbow trout - 600 IU, herring oil - 800 IU, canned fish - approx. 200 IU),
  • butter (60 IU in 100 g),
  • liver (in 100 g of beef liver - 560 IU, mackerel liver - 9600 IU, and tuna liver as much as 130,000 IU)
  • egg yolks (54 IU in one yolk).

The main food source of vitamin D3 is fatty sea fish, very little popular on Polish tables. Intake of Vitamin D3 with food is insufficient to cover itthe body's demand for this ingredient in periods of too little sunlight. For this reason, in Polish conditions, supplementation is a must.

Most dietary supplements on the Polish market contain vitamin D3.Very often supplements are made of fish oils from the liver of various fish, because fish livers are by far the richest source of vitamin D3 .

However, you need to be careful when choosing foods enriched with vitamin D, such as plant-based drinks such as soy milk, almond or oat milk, and fruit juices. Due to the fact that vitamin D2 is cheaper to produce, food is usually fortified with vitamin D2.

How much vitamin D3 should you take per day?

In Polish conditions, vitamin D supplementation is a mustand is recommended in every population group. Recommended doses of vitamin D for daily intake are expressed in IU (international units) or, less frequently, in μg.

Currently, in Poland, adults are recommended to supplement at the level of 800 to 2000 IU per day (depending on the supply in the diet) from October to April, and if the person is not in the sun in the spring and summer period, at least 15-20 minutes a day between 10-15 hours with exposed arms, lower legs and face, supplementation is recommended throughout the year.

Official recommendations are made without distinguishing between vitamin D3 and D2. In the light of the latest scientific research , it is definitely more beneficial for the body to choose vitamin D3, the same amount of which has a stronger effect than vitamin D2 . Probably over time and with the appropriate amount of scientific data, the official recommendations will distinguish between the dosage of vitamin D2 and D3.

The physiological role of vitamin D3 is exactly the same as that of vitamin D, as vitamin D3 is part of vitamin D.

The difference between vitamin D3 and D is that vitamin D3 is the form preferred by the body, more efficiently converted into the active compound, showing much more effectiveness than a mixture of chemical compounds, which is vitamin D, and in particular more effective than vitamin D2.

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