Vitamin D is a fascinating nutrient! From actually functioning as a hormone in the body, to being synthesised from sun-bathed cholesterol in our skin, this vitamin is really unique. Many of us know it for its ability to regulate calcium absorption and maintain bone mineral density, but it is also an extremely important vitamin (or hormone) for immune function.
Last week we spoke about Vitamin A as the nutrient which helps to build a strong fortress, and we’ve previously spoken about the many different roles Vitamin C plays in maintaining a strong immune defence. By now, you should be getting the picture that the immune system depends on a whole range of different nutrients to keep us fighting fit.
So how does Vitamin D fit into the defence force of our immune system? Well, Vitamin D is all about peacekeeping and protection.
Vitamin D is essential for the effectiveness of the innate immune system, which can be thought of as the first responders and protectors against harmful pathogens once they breach our defensive walls. They’re not quite as specialised or targeted in their response, but sometimes it pays off to get onto an infection as quickly as possible.
Macrophages are an important type of these first responder cells, and their main function is to engulf, digest and destroy harmful pathogens. Macrophages need Vitamin D in order to start producing antimicrobial peptides which breakdown pathogens once they’ve been swallowed, such as beta defensin 4 and cathelocidin (really impressive and powerful sounding protective proteins).
Vitamin D can also be thought of as the internal peacekeeper. It makes sure all of the different immune cells know who is on their side, are on the same page, and getting along well.
When the immune system is on such high alert, it needs to be able to quickly differentiate between friend and foe, between the cells which make up our body and the cells which are invading pathogens. Vitamin D helps make sure that the immune system has proper systems in place so that they can quickly tell the difference.
Without Vitamin D, things get heated, immune cells go rogue and start attacking everything including the body. When the body starts attacking itself like this, it is known as autoimmune disease and low levels of vitamin D have been consistently correlated with a higher prevalence of these conditions.