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Vitamin D3 has a therapeutic effect on infections and diseases

- which vitamin D2 does not have

Vitamin D3 has a therapeutic effect on infections and diseasesVitamin D2 occurs naturally in foods from the plant kingdom while vitamin D3 comes from animal sources. It is also vitamin D3 that we synthesize in our skin in response to sun exposure. Scientists from the Universities of Surrey and Brighton in Great Britain have now discovered that the two types of vitamin D have entirely different effects. They therefore sow doubts about vitamin D2’s role in human health, whereas vitamin D3 is known for its vital role in helping the immune system in its fight against infections such as COVID-19. Most cells in the body have vitamin D receptors, and the nutrient is also important for cancer prevention, the nervous system, our mood, and a number of other functions. Vitamin D3 from food, supplements, or sunshine must be activated in the body before it can be utilized.

Vitamin D is a lipid-soluble nutrient found in various forms with similar chemical structures.

  • Vitamin D2 (ergocalciferol) is found in certain plants such as fungi that synthesize this form of vitamin D2 from UVB radiation
  • Vitamin D3 (cholecalciferol) is found in high-fat animal foods such as cod liver, herring, salmon, dairy cream, and eggs.
  • Humans synthesize cholecalciferol in their skin in a process that involves UBV rays from the sun and a cholesterol precursor
  • In the liver, both D2 and D3 are converted into calcidiol. This form of vitamin D is what we measure in blood samples. It is known as 25-hydroxytivitamin D3 – or 25(OH)D
  • Calcidiol is then converted in the kidneys, in the white blood cells of the immune system, in the blood vessels, and in certain other tissues. Calcidiol is converted into calcitriol (1,25-dihydroxyvitamin D3), which is the active steroid form of vitamin D

It is calcitriol that binds to the vitamin D receptors in most of the body’s cells, and it is also this form of vitamin D that regulates a host of different biochemical processes in the body and controls around 10 percent of our genes, some of which are important for our immune response, cancer prevention, nervous system, mood, blood sugar levels, and many other things.

Vitamin D3 is most effective for activating genes and signal systems in the immune system

The scientists from the Universities of Surrey and Brighton in Great Britain have studied the effect of daily supplementation with 15 micrograms of vitamin D2 or 15 micrograms of D3 for 12 weeks during the winter period. The participants were healthy British women of European or South-Asian descent in the ages 20-64 years. The researchers looked at the activity of certain genes and signaling pathways. Contrary to popular belief, it turned out the two types of vitamin D did not have the same effect. The scientists discovered that vitamin D3 had a measurable effect on the immune system by stimulating the body’s type 1 interferon signaling pathway. Type 1 interferons are part of the immune system and work by mobilizing the body’s first-line defense against viruses and bacteria. That way, the “storm troops” of the immune defense can fight most germs before they make us sick. Type 1 interferons also play an important role in the regulation of inflammatory processes, activation of T cells, and fighting cancer cells.
Having adequate amounts of vitamin D3 in your blood can therefore help prevent bacteria and virus from gaining foothold in the body and from replicating and causing infections. Vitamin D3 also has a host of other important functions in the body and helps protect against osteoporosis and a number of other diseases.
Interestingly, the scientists did not find that vitamin D2 had the same effect on gene activities, interferons, and the immune defense.
The study data even showed that participants of European and South-Asian lineage reacted differently to the two types of vitamin D. The researchers therefore call for additional studies of vitamin D.

  • Our diets normally don’t provide vitamin D, yet some foods may be enriched with this form of the nutrient.
  • It is easier and faster for humans to convert vitamin D3 (into calcitriol) from sunlight, fatty animal food sources, and supplements.

We need supplements of vitamin D3

According to the scientists, vitamin D deficiency is particularly widespread during the winter period and in areas with limited sunlight. The COVID-19 pandemic has made the problem even worse by forcing people to spend far more time indoors. Face masks also limit the vitamin D synthesis in skin. In addition, older people, people with dark skin, diabetics, overweight individuals, and chronically ill have difficulty with producing or activating vitamin D.
It is therefore recommended for all people to take vitamin D supplements during the winter period and if they are low in the nutrient. It is important to choose vitamin D3, as this form has a documented effect on our health, unlike vitamin D2. Vitamin D3 should also be used for food fortification, even though it is a more expensive vitamin source. The new study is published in Frontiers in Immunology.

Vitamin D supplementation and requirements

The Danish Veterinary and Food Administration recommends for everyone to take a vitamin D supplement during the winter period, and vulnerable groups should supplement with the nutrient all year round. Our actual vitamin D requirement hinges on many different things such as sun exposure, age, skin type, BMI, and chronic illnesses. It pays off for everyone to strive for optimal vitamin D levels in the blood at all times.
EU’s Scientific Committee on Food has established a safe daily upper intake level of 100 micrograms of vitamin D for adults – including pregnant and breastfeeding women.
Vitamin D is a lipid-soluble nutrient. In supplements, vitamin D therefore works best when it is dissolved in oil in gelatin capsules.


Louise R, Durrant et al. Vitamin D2 and D3 Have Overlapping But Different Effects on The Human Immune System Revealed Through Analysis of The Blood Transcriptome. Frontiers in Immunology, 25 February 2022

University of Surrey. Study questions the role of vitamin D2 in human health but its sibling, vitamin D3, could be important fighting infections. ScienceDaily. February 25, 2022

J. Wesley Pike and Mark B. Meyer. Fully-activated Vitamin D (calcitriol) is produced inside and outside of the kidneys. J Clin Invest 2020

Interferon type I - Wikipedia

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