Vitamin D – The Immune System Regulator Nutrient

Vitamin D absorption

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By Raf Ganzaroli

According to a 2010 report, published in Genome Research, Vitamin D influences several hundred genes, many of which control disease suppression or expression. It also states that Vitamin D is an epigenetic controller, it regulates what our genes are doing, and its deficiency also increases our susceptibility to autoimmune conditions like multiple sclerosis, rheumatoid arthritis, and type 1 diabetes. 

What is Vitamin D?  

It’s Group of fat-soluble steroids hormones primarily produced in the skin in response to the interaction with UVB radiation from sun light and absorbed from food that we eat.

Approximately 10% of our vitamin D intake comes from food, while 90% comes from interaction with the sun light. 

How does the body turn the sun light into useable vitamin D? 

The UVB hits the skin and interacts with a compound called 7-dehydrocholesterol – cholecalciferol, knows as vitamin D3. Vitamin D, goes to the blood stream and is transported to the liver, which will be responsible to transform Vitamin D into the compound called, 25-hydroxycholecalciferol. This form is the one that normally is measured via blood test to assess the levels of Vitamin D. From the liver, this compound will move to the kidneys where it is converted into its final form called 1.25-Dihydroxycholecalciferol, known as Calcitriol, which is the final and useable form of Vitamin D. 

It may be complex to understand this entire process above, however, the idea is to understand that the process in the body is integrated and rely on different organs, especially the kidney, which is underrated in this process. With that said, the right functioning of these organs is vital to the whole activation process of Vitamin D. 

What are the main roles that Vitamin D plays on our bodies? 

Vitamin D receptors are found in nearly all, if not all, of the cells in the human body, which makes a prominent in demand nutrient for cellular function.

Let’s highlight 3 main ones: 

Immune System

Vitamin D is a well-noted immunomodulator. Immunomodulation is the ability of the immune system to increase or decrease its activity when needed. If we’re talking about autoimmunity (when the immune system is over-reactive), we want to help the immune system to be a little bit more subdued and bring its activity down or get it back to a baseline and not hyperactive. Whereas when we are talking about a situation where the body is defending itself against an infection for example, we want a heightened immune response to be able to take out the invader or the infectious cells in the body. 

Bone density 

Vitamin D is required to absorb calcium in the gut, from food, into the bloodstream. Having low levels of Vitamin D in the body, results in failure to control calcium homeostasis and therefore increasing osteoporosis risk. Issues related to bone density in postmenopausal women are quite high according to plenty of studies and one of the main causes is Vitamin D deficiency.

Sex Function

If Vitamin D is a steroids hormone, we expect that it plays a role on sexual functioning. A study published on The International Journal of Impotence Research, found that vitamin D deficiency in men (18-40 years old) was related to low scores for erectile function, orgasmic function, and sexual desire. 

How can I optimize the Vitamin D absorption? 

Getting sun light about 15 to 20 minutes daily with no sunscreen. Darker skins might need a bit more, about 30 minutes daily due to the high level of melanin, which acts a barrier to let the UVB penetrates in the skin. 

Food Sources

Only a few foods naturally contain Vitamin D. The best sources are listed below:

  • Oily Fish – Salmon, sardines, herring, mackerel 
  • Mushroom
  • Beef liver 
  • Egg yolks 

Is supplementation necessary? 

Supplementation is recommended, whenever Vitamin D levels in blood are suboptimal and was not corrected by natural exposure. Vitamin D deficiency is defined as a 25(OH)D below 50 mol/L and Vitamin D insufficiency as a 25(OH)D of 72.5 nmol/L.

We recommend all of our Clients & Patients to get their Vitamin D levels checked at least twice per year, specially during winter. If you need to get your Vitamin D levels checked, please get in touch and we will refer you to a blood collection lab.


Osteoporosis and Vitamin-D Deficiency Among Postmenopausal Women with Osteoarthritis Undergoing Total Hip Arthroplasty – The Journal of Bone & Joint Surgery 

The effect of low vitamin D status on sexual functioning and depressive symptoms in apparently healthy men: a pilot study – International Journal of Impotence Research

Factors that influence the cutaneous synthesis and dietary sources of vitamin D – Archives of Biochemistry and Biophysics.

Vitamin D and Immune Function – Journal Nutrients 2013


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