No Worries – why it’s vital to address stress by Petronella Ravenshear, psychoneuroimmunologist and author of The Human Being Diet
Fight or flight, our ancient reaction to a serious threat, stimulates specific parts of the immune system, including the inflammatory response, to help us survive imminent danger. Digestion, detoxification and repair, and all the processes that aren't necessary for our immediate survival, are temporarily deactivated. At the same time, some parts of the immune system are also switched off - the body isn't going to put precious energy or resources into fighting any kind of virus when there's an imminent life-or-death situation to deal with.
In an emergency, we need the big guns (non specific immunity) and their scattergun effect on the battlefield, rather than the specialised (specific immunity) snipers and their guns, which just deal with one enemy soldier at a time. We evolved, along with our immune system, to deal with short sharp shocks and then life would return to normal.
But when the stress is ongoing, as with many issues in our daily lives (mortgages, redundancy, fear of the unknown) and we keep producing stress hormones, including cortisol, which suppresses immunity, we experience something called low-grade inflammation. The inflammation and the immune system are chronically activated, though at a low level. With chronically high cortisol levels there is a decrease in the body's lymphocytes- the white blood cells that help fight infection. The lower the lymphocyte level, the more at risk we are of picking up viruses, including colds and flu. That's why it's viral for our overall health to take the pressure off, because stress and the immune system go hand-in-hand.