Now more than ever, it is important for us to keep ourselves as strong and healthy as we can be. Whilst we would traditionally look to vitamin C to boost our immune system, recent studies have also uncovered fresh insights into the positive affects vitamin D has on the immune system as well as its well-known actions of promoting bone health and calcium homeostasis.
How can vitamin D support the immune system?
The immune system protects the body from foreign, invading organisms and promotes protective immunity. Recently the implications of vitamin D deficiency on the immune system have become clear and those with the deficiency have become more susceptible to infection, particularly those with autoimmune diseases.
Multiple studies suggest the association between lower levels of vitamin D and increased infection. One study reported that those with lower levels of vitamin D were more likely to report upper respiratory tract infection than those with sufficient levels. Another study showed that vitamin D administration to school children resulted in a significant decrease in influenza infection.
The phagocytic killing ability of immune cells such as natural killer cells, macrophages and neutrophils is increased by vitamin D. It also reinforces physical barriers of epithelial cells by maintaining tight junctions. These defences can be highly effective in limiting or preventing progression of infection, resulting in mild symptoms or no symptoms at all.
What is the recommended daily dose of vitamin D and where do I get it?
Public Health England suggest 400 IU/10 mcg may be adequate to ward off the effects of severe deficiency which results in rickets, it is far to low to achieve optimal balanced immune function and the prevention of many other diseases. Studies show that at least 3000IU per day is required to maintain optimal blood levels. This can come from food (such as oily fish, red meat and liver), sunlight and supplements. Although it is preferable to obtain vitamin D from sensible sun exposure, during the winter period in the UK (September to April) it could be necessary that a significant proportion of this dose will need to be supplemented as the winter UVB light is no sufficient enough to maintain these levels of vitamin D.