The role of Vitamin D in Immunity (SQ-127)You need vitamin D for strong bones and muscles. Without it, your body cannot absorb calcium and phosphorus from the intestines. It appears vitamin D may also play a key role in boosting your immunity. In this article, let’s explore how vitamin D affects immune system.
Vitamin D and immunity
What is the role of vitamin D in the body? Is it for immunity? Can low vitamin D levels cause low immunity?
It appears that vitamin D deficiency not only makes you prone to getting sick often, it also increases the risk of autoimmunity. It is because vitamin D has a balancing effect on your immune system.
Your immune system defends the body from foreign organisms like bacteria and viruses. But it also maintains tolerance to self, that is, your immune cells have a way of not destroying its own cells and tissues. And vitamin D plays a key role in maintaining both these aspects of immune functionality.
Studies have found that low vitamin D levels can increase one’s risk of developing upper respiratory conditions and aggravate asthma symptoms. Poor levels are also associated with tuberculosis, and chronic obstructive pulmonary disease (COPD). 
In 2017, a review of 25 randomised clinical trials showed that vitamin D supplementation may significantly reduce the risk of developing respiratory infections such as cold and flu. And this benefit was greater in people with sever vitamin D deficiency.
Researchers concluded that “Our study reports a major new indication for vitamin D supplementation: the prevention of acute respiratory tract infection. We also show that people who are very deficient in vitamin D and those receiving daily or weekly supplementation without additional bolus doses experienced particular benefit.” 
A 2010 study found that 1,200 IU of vitamin D per day for 4 months reduced the risk of influenza A infection by over 40% in school going children, during winters. 
Experts believe vitamin D boosts immunity and reduces inflammation, two important reasons why supplements may be effective in preventing and fighting acute respiratory tract infections.
“Studies show that vitamin D boosts immunity and supplements may help in reducing the risk of upper respiratory infections. These benefits are greater in people with severe vitamin D deficiency.“
How does vitamin d affect the immune system
Vitamin D affects your overall immunity in more ways than one.
Every cell in the body has receptors for vitamin D. These are called vitamin D receptors or VDRs. Your skin, intestines, lungs, brain, heart muscles, skeletal muscles and your immune cells contain these receptors. Even your endocrine glands like thyroid gland have receptors for vitamin D.
Vitamin D binds to receptors in cells and controls the synthesis of various proteins that your body needs to carry out a wide range of functions – to survive and to be healthy.
How does this work? Vitamin D from the bloodstream attaches with receptors present in target cells, making them active. These active receptors switch on some genes that synthesise many different proteins and enzymes that control how your body function.
For example, vitamin D binds with the receptors on cells in your intestines. These receptors turn on the genes that make proteins responsible for absorbing calcium in the intestines.
Similarly, vitamin D also binds to receptors on white blood cells. This switches on genes that synthesise anti-microbial proteins, such as cathelicidin and β defensin 2. These proteins work as natural antibiotics and help the body to fight a range of bacterial and viral infections. This is how vitamin D boosts natural or innate immunity.
Your innate immunity is your first line of defense against pathogens. It kicks in almost immediately your body comes in contact with foreign bodies such as bacteria, fungi and viruses.
It has come to light that various types of immune cells, for example monocytes, macrophages, dendritic cells, T cells and B cells, all have receptor sites for vitamin D. In addition, these cells also contain enzymes that are needed to convert circulating vitamin D (which is not very active) into more active form 1,25(OH)₂D.
“Vitamin D stimulates the production of anti-microbial proteins within the body, which helps boost natural immunity and fights infections.”
Vitamin D and auto-immunity
The way vitamin D affects immune health is a complex process. It keeps a balance between natural and adaptive immunity. While natural immunity is crucial to fight infections, adaptive immunity is what is responsible for reducing the risk of auto-immune disorders.
So, you need a well-balanced immune system, active enough to keep frequent infections at bay and tolerant enough to prevent auto-immune diseases.
Adaptive immunity kicks in when your natural immunity is not able to destroy the pathogens. B and T cells are the main soldiers of adaptive immunity. These cells make antibodies that kill invading pathogens. Antibodies bind to antigens – proteins present on the surface of pathogens or foreign bodies. B cells also make memory cells that remember the pathogen. This helps launch a faster attack next time immune cells come across the same antigen.
Vitamin D boosts your natural immunity, but it also regulates adaptive immunity and keeps your immune system from going into an overdrive. How does it work?
You have various kinds of T cells in the body. This includes T regulatory cells, also known as Tregs. These Tregs makes the immune system tolerant towards its own cells, building self-tolerance. Tregs play a very important role in preventing auto-immunity. It appears that people with autoimmune diseases may have malfunctioning or reduced levels of Treg cells in their body.
Studies show that Vitamin D supplementation may improve the number and function of Treg cells. 
Another study found that vitamin D regulates the activation of T cells. In healthy people, T cells help fight infections, whereas in people with autoimmunity, T cells can go haywire – attacking the body’s own cells, causing damage and disease. How does vitamin D fit with controlling T cell’s activation?
T cells are activated when they come in contact with dendritic cells, another type of immune cell. In this study, researchers found that vitamin D made dendritic cells to make more of a molecule called CD31 on their surface. CD31 prevented the contact between dendritic cells and T cells, thus inhibiting the activation of T cells. 
“Vitamin D not only strengthens natural immunity, that keeps infections under control but also regulates adaptive immunity, that prevents autoimmunity.”
Vitamin D deficiencyVitamin D plays a vitally important role in your health. And it is easy to maintain adequate levels, either through exposing your skin to sunlight or by taking quality vitamin D3 supplements. In spite of this, vitamin D deficiency is identified as one of the most prevalent nutritional deficiencies world-wide.
What causes a vitamin D deficiency?
While insufficient exposure to the sun is one of the major reasons why vitamin D deficiency is so rampant, there are plenty of other reasons for reduced levels of Vitamin D:
- Increased use of sunscreen
- Health conditions, such as celiac and Crohn's disease, that cause problems in vitamin D absorption.
- Chronic liver and kidney problems
- Old age
- People with darker skin tone
- Use of statin drugs
- Magnesium deficiency
Low vitamin D symptoms
Some of the most early and noticeable symptoms of vitamin D deficiency are body pain, achy bones, muscle weakness and fatigue. However, you may have other sneaky symptoms indicating low vitamin D levels, such as:
- Depression and irritability
- Excessive head sweating
- Hair loss
- Erectile dysfunction
- Getting sick often
- Inability to sleep
- Bloating or constipation
What happens if vitamin D is low?
Long term vitamin D deficiency comes with severe health consequences.
One of the most well-known outcomes of low vitamin D levels is weak bones that are prone to fractures. It can lead to rickets in children and osteomalacia in adults.
We already discussed how vitamin D deficiency impacts your immunity, increasing your risk of infections. Low levels can cause increase the odds of allergies, asthma, dry eyes, autoimmune diseases such as thyroid and irritable bowel syndrome, and diabetes. Vitamin D deficiency is even known to affect your sleep, brain health and emotional well-being. Studies show that low vitamin D levels are related to increased risk of depression.
Pregnant women need healthy levels of vitamin D for healthy pregnancy. Low levels can not only increase the risk of premature delivery, miscarriage, and gestational diabetes in mothers, it can also impact growth and development of their unborn child. Vitamin D deficiency in mothers may even increase the risk of low birth weight, wheezing disorders, allergies, asthma, and obesity in children.
“Vitamin D deficiency causes weak bones. It also causes many health problems including bone pain, fatigue, allergies, asthma, heart disease, dry eyes, thyroid and diabetes. Poor levels in pregnant women can cause health complications during pregnancy and health issues in infants such as risk of allergies, wheezing disorders and poor growth. “
How can you improve your vitamin D levels?
Your body makes vitamin D on its own when you expose your skin to sunlight. And this can happen only in the presence of UVB rays, available when the sun is higher than 45 degrees above the horizon. How do you check this? If your shadow is shorter than your actual height, it means your skin is making vitamin D.
Just 15 to 20 minutes of sun exposure, preferably between 10.00 am to 3.00 pm, is a good strategy to boost your vitamin D levels naturally. The time you need to spend in sun also depends on your skin tone. For example, if you have a darker skin tone, you may need to expose your skin for 30 minutes or maybe a little longer to make healthy levels of vitamin D.
If you have skin cancer or you think you might be at risk, and need to avoid going out in the sun, taking vitamin D3 supplements is a safer option to build up your levels.
Choosing the right kind of supplement is important, especially if you have issues with absorption due to such ailments as Celiac or Crohn's disease. In this case, a high-quality liposomal vitamin D3 supplement is your best bet. But taking vitamin D3 alone is not likely to help.
If you are looking to improve your D levels, it is important to take magnesium. Without magnesium, your body is not able to use any of the vitamin D, whether it is coming from sun exposure or through supplements.
How does it work? Firstly, nearly all enzymes that process vitamin D in the body need magnesium to work. Secondly, magnesium converts vitamin D into its active and usable form.
Vitamin D3 supplements come in handy if you are not getting enough exposure to the sun or you need to avoid the sun due to a medical condition. It is important that you have a magnesium-rich diet or take magnesium supplements to get the full benefits of vitamin D. Magnesium helps the body absorb and use vitamin D effectively. Magnesium deficiency can interfere with vitamin D absorption.
Can vitamin D reduce your risk of COVID-19?
Vitamin D improves immune health. Does it mean taking vitamin D3 supplements can help you lower your risk of COVID-19?
We don’t have enough scientific evidence yet to suggest this. But in general, vitamin D3 supplementation is effective in reducing the risk of respiratory tract infections. Also, vitamin D deficiency impairs your immune health, making you prone to infections.
Some very recent research, though in early stages, found that vitamin D status may play a role in determining the risk of dying from Covid-19. The researchers noted that countries where people have low vitamin D levels had a higher number of cases and deaths. 
What is the co-relation?
Let’s go back to adaptive and innate immunity. B and T cells, cells of adaptive immune system, also produce cytokines – these are messenger proteins that attract more immune cells to the site of infection.
When a virus like coronavirus attacks, the adaptive immunity is not able to recognize the virus and launches a fierce attack to destroy it, resulting in over production of cytokines – creating a cytokine storm that spreads beyond the local tissue and triggers inflammation. This is when immune cells start attacking healthy tissue.
In people who develop COVID-19, this cytokine storm causes damage to the lung tissue – causing inflammation and fluid build-up in the tiny air sacs in your lungs. This means your lungs are not getting enough oxygen. This condition is called acute respiratory distress syndrome or ARDS. It may even lead to death as less and less oxygen reaches the bloodstream, depriving organs of the much-needed oxygen.
What vitamin D does is bind to the receptors on the immune cells and switches off certain genes responsible for production of cytokines – leading to less inflammation and less likelihood of a cytokine storm that can cause damage to healthy lung tissue, and eventually ARDS.
So, while vitamin D activates genes that are involved in production of anti-microbial proteins in the body, it also turns off genes involved in production of cytokines. This helps both natural and adaptive immune systems to work in harmony and balance.
Connecting the dots, a 2015 study also showed that vitamin D deficiency may contribute to the development of ARDS. 
The finding is not definitive, but it can certainly give your immunity a much needed boost that you need to fight respiratory infections and keep inflammation in check, which is one important aspect in COVID-19 infection.
There is enough scientific evidence to suggest that vitamin D deficiency increases your chances of infection, especially respiratory tract infections. Taking vitamin D3 supplements can be a safe way to keep your immune health in top shape and reduce your risk of respiratory illnesses.
How much vitamin D should I take to boost immune system?Taking 2,000-4,000 IUs of vitamin D3 per day is generally considered safe to maintain healthy levels. According to the NHS, it is not advisable to take more than 4,000 IUs of vitamin D per day for adults over an extended period.
Improving your vitamin D levels is important to prevent weak bones, achy joints, and general weakness. But considering the role of vitamin D in boosting immunity, it can also help you protect yourself from infections and disease.
- Hejazi et al. A review of Vitamin D effects on common respiratory diseases: Asthma, chronic obstructive pulmonary disease, and tuberculosis. J Res Pharm Pract. 2016
- Martineau et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ, 2017
- Mitsuyoshi Urashima, Takaaki Segawa, Minoru Okazaki, Mana Kurihara, Yasuyuki Wada, and Hiroyuki Ida. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010
- Fisher et al. The role of vitamin D in increasing circulating T regulatory cell numbers and modulating T regulatory cell phenotypes in patients with inflammatory disease or in healthy volunteers: A systematic review. PLoS One. 2019.
- Sau et al. 1,25-Dihydroxyvitamin D3 Restrains CD4+ T Cell Priming Ability of CD11c+ Dendritic Cells by Upregulating Expression of CD31. Frontiers in Immunology. 2019
- Daneshkhah et al. The Possible Role of Vitamin D in Suppressing Cytokine Storm and Associated Mortality in COVID-19 Patients. April 2020.
- Dancer et al. Vitamin D deficiency contributes directly to the acute respiratory distress syndrome (ARDS). Thorax. 2015