Vitamin D: Do you know what is it used for?

Welcome to this new article! Today I’m going  to talk to you about vitamin D, I’m sure you know or have heard about it, it’s quite famous. Shall we analyze it in a more scientific way?

Let’s start by explaining what vitamin D is

It is an organic nutrient present in very small quantities in food that helps develop specific and vital functions for the cells and tissues of the body.
It is classified as a fat-soluble vitamin; it is absorbed with fat and eliminated thanks to its metabolism in the liver and excreted by the bile and feces. [1]

What is vitamin D for?

I could go on for a long time in this section since it has many functions, and it is suspected that most of them are still unknown to us, so I am going to highlight some of the most important ones.

• It participates in the metabolism of calcium and phosphorus. [1]
• Modulates the immune system (I.S., defense system). [1] [5]
• It regulates pancreatic insulin secretion (hormone that regulates blood sugar). [2]
• It contributes to the proper functioning of the skeletal muscles. [1]

Lack of vitamin D

The lack of vitamin D alters bone mineralization leading to rickets in children and osteomalacia and osteoporosis in adults, also an alteration of calcium homeostasis may occur, causing the following symptoms: neuromuscular irritability, numbness, paresthesias, tetany, and sometimes convulsions. [1]

Vitamin D deficiency has also been associated with:

• Weakness.
• Chronic fatigue.
• Obesity. [10]
• Autoimmune diseases: type 1 diabetes, multiple sclerosis, rheumatoid arthritis, psoriasis, high blood pressure. [1] [2]
• Cardiovascular diseases and mental illness. [2]
• Some kidney and liver diseases.

In these cases, however, the deficiency would be due to the inflammatory state present in these pathologies.

Groups at higher risk of deficiency: children and women of Asian or African origin in areas with poor sunlight, the elderly and homebound, breastfed babies  during the winter, strict vegetarians. [5]

Groups at risk of deficiency: the majority of the population. [6] [7]

How to obtain vitamin D

Now that we know how important it is, we need to know where we can get this vitamin D that can help us improve our health.

The sunshine vitamin, or as I call it: the cholesterol vitamin

Many people believe that this vitamin is present in the sun, so they try to sunbathe often, although the vitamin isn’t exactly in the sun, but our skin has the potential to get it through ultraviolet light. The process summarized would be as follows:

1. Ultraviolet light when it comes into contact with the skin transforms 7-hydrocholesterol into pre-vitamin D3. [1]
2. Pre-vitamin D3 is converted into cholecalciferol, which is then transported in the bloodstream to the liver. [1]
3. Cholecalciferol is transformed in the liver into 25-hydroxycholecalciferol (calcidiol, precursor of the active metabolite). [1]
4. Some of the vitamin is stored in the liver as calcidiol. [1]
5. From the liver, calcidiol is transported in the blood bound to DBP (Vitamin D Binding Protein) to the kidney or other stores (fat or muscle). [1]
6. In the kidney, the activation of vitamin D is produced thanks to the action of parathormone (secreted by parathyroids) transforming 25-hydroxycholecalciferol (calcidiol) into 1,25-hydroxycholecalciferol (calcitriol). [1]

Food sources of vitamin D

We can also obtain this vitamin through foods that contain it. Although many sources consider that the dietary intake alone is often insufficient. This process occurs as follows:

1. The absorption of ergocalciferol (D2) and cholecalciferol (D3) occurs at the level of the small intestine with the presence of fats and bile salts. [1]
2. It is transported via the lymph and blood to the liver. [1]

Foods rich in vitamin D are worth including in the diet (not only because they are rich in vitamin D, but also because they are healthy): eggs, butter, sardines.

Supplementation

There is some confusion and/or controversy about the format of supplementation and the amount needed.

As for the format, there are two common forms of prescription:

• Hidroferol. [8]
• Colecalciferol (D3).

As for the recommended amounts, here are some references:

• According to the Food and Nutrition Committee of the National Institute of Health (NIH) of the United States [8]
  
• According to Dr. Holick
  

My recommendation

The best way to ensure that we get our vitamin D levels naturally is through sunlight. But there are periods of the year when we cannot do this, so to take advantage of the benefits of the sun I urge you to follow these tables if you are living in the Iberian Peninsula.

Therefore, I recommend the supplementation of vitamin D3 (Cholecalciferol) daily [3] during lunch or dinner [4], from November to February to contribute to better health during the months when we are more vulnerable to colds, flu, and other infections.

What factors should we take into account when sunbathing? [8]

• Clouds block about 50% of solar radiation (UV), and 60% if they are pollution clouds.
• The glass interferes with the passage of UVB, and does not allow us to synthesize vitamin D.
• Sunscreens hinder the absorption of UV.
• It seems that exposure to the arms, legs, face, or back would be sufficient (although I prefer as much exposure as possible to be sure)
• It’s important to remember that we need to protect ourselves from the sun since exposure to solar radiation is a risk factor in the development of skin cancer (melanoma) and in epithelial aging, so I recommend extreme caution and not to exceed the recommended times.

In any case, this topic deserves much more space, but I didn’t intend to make this article too long, so I’ll publish more information in a future article (for example: skin types, sunscreens, smog effect, burns, vitamin D megadose, role in autoimmune diseases, vitamin D and K, vitamin D and magnesium, …). If you are interested in learning more about strengthening the immune system and reducing inflammation, I recommend you read my article about omega 3: https://felixmora.com/laverdadacercadelos-omega-3/

You will find related links and extras below, I hope you enjoy it and find it useful.

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4924160/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3571641/
3. https://www.ncbi.nlm.nih.gov/pubmed/17874029
4. https://onlinelibrary.wiley.com/doi/full/10.1002/jbmr.67
5. http://www.mscbs.gob.es/biblioPublic/publicaciones/recursos_propios/resp/revista_cdrom/vol86/vol86_5/RS865C_453.pdf
6. http://www.revistadeosteoporosisymetabolismomineral.com/pdf/articulos/12010020200070009.pdf
7. https://www.aepap.org/sites/default/files/017-030_vitamina_d_por_encima_del_ano.pdf
8. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
9. https://www.sciencedirect.com/science/article/abs/pii/S0960076016302199
10. http://drholick.com/

Interesting Cochrane systematic review of vitamin D in pregnancy:
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD008873.pub3/full/es

Systematic review very useful in the treatment of asthma:
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011511.pub2/full/es#CD011511-sec1-0005

Reducing mortality in the elderly, another review:
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD007470.pub3/full/es#CD007470-sec1-0001