Vitamin D Benefits.
It's been known for years that vitamin D is essential for maintaining healthy bones and teeth. Without it, bones can become thin and brittle.
But did you know that Vitamin D also plays an important role in helping immune systems function?
Low levels of vitamin D can lead to autoimmunity. This is when the immune system attacks healthy cells and the potential for infection increases.
The immune system is like an army that prevents invaders, such as viruses and bacteria, from taking over the homeland, (your body). It is composed of the innate and adaptive immune systems.
Let's say a virus is present in a patient's lungs, specifically in the air sacs (alveoli), which can lead to acute respiratory distress syndrome (ARDS).
The first line of defense is a healthy immune system:
Now, the innate immune system comes into play immediately or within hours of antigen detection. Antigens are proteins on the surfaces of bacteria, fungi and viruses that the body doesn’t recognize as its own.
Natural killer cells and macrophages, along with other immune cells, recognize, engulf and destroy pathogens. The main purpose of these cells is to prevent the spread and movement of harmful substances throughout the body. They are akin to soldiers shooting indiscriminately all over the enemy's camp.
Although the exact role of vitamin D in the immune system is not fully understood, studies have shown it may influence both innate and adaptive immune systems.
When the innate immune system is activated, its cells turn certain genes on to become more efficient at killing pathogens. Vitamin D binds to these cells and enhances this transformation, helping the innate immune system kill viruses.
The innate immune system and vitamin D
The second line of defense is the adaptive immune system:
It relies on B cells and T cells to carry out its tasks. These cells produce billions of antibodies. Antibodies recognize antigens and bind to them. They are like high-ranking officers that conduct specific missions targeting only certain enemies. Antibodies make future responses against a specific antigen more efficient.
“The problem with infections such as COVID-19, is that most of us are believed to be naïve to the infection. So we don't have memory B cells ready, which means that adaptive immunity, even though it might be super powerful, can't recognize the pathogen,” says Vadim Backman, professor of biomedical engineering at Northwestern University.
Cells of the adaptive immune system produce cytokines. These small proteins attract more immune cells and trigger inflammation. Sometimes, cytokines become too abundant and create a cytokine storm – when immune cells spread beyond infected body parts and attack healthy tissue.
“The way our immune system responds to the virus may be a big part of this puzzle,” Backman says. “What does seem to be critical is acute respiratory distress syndrome.” ARDS is caused by an overreaction of the immune system “called a cytokine storm, which seems to be induced by the adaptive immune system,” Backman says.
Backman says Vitamin D binds to the cells of the adaptive immune system and turns some genes on while switching others off. This causes cells to produce fewer cytokines, reducing inflammation and the possibility of cytokine storm.
Possible link between vitamin D deficiency and COVID-19
The research is in the early stages. According to a preprint study Backman co-wrote, countries with low average vitamin D blood levels in the population had higher numbers of COVID-19 cases and deaths. A study from the U.K. looked at the nearly 450 patients diagnosed with COVID-19 and did not find a link between vitamin D concentrations and risk of COVID-19 infection.
In a paper published in the British Medical Journal, 21 experts from the U.K., Ireland and the USA concludes that although vitamin D is “essential for good health” and may bolster the immune system, it can be dangerous in high doses.
Worldwide, about 1 billion people have inadequate levels of vitamin D in their blood, and insufficiency affects almost 50% of the population. Most commonly, low levels of vitamin D are caused by insufficient exposure to sunlight.
“One important aspect for us to understand is that all evidence about vitamin D right now comes from indirect observational studies, Backman says about his research related to COVID-19. The gold standard study would be to have a randomized placebo controlled design. And we hope that the indirect evidence related to vitamin D can stimulate these kind of studies.”