Someone saying that they have a “weak immune system” is something that really irritates me as it’s simply not true – or rather it’s not accurate – and when you ask the person to clarify what they mean they say something like “oh I get ill all the time”. Your immune system can broadly be split into 2: the innate immune system; and the learned immune system.
Your innate immune system is made up of things like your skin, your stomach acid, certain types of white blood cells, mucus, saliva, your blood brain barrier, the gut lining, and other bits and pieces. This is your first line of defence against things that are a threat to your body and should stop a lot of stuff getting in in the first place. We then have our learned immune response which we develop throughout infancy and childhood and is influenced by our exposure to infections, and whether we grew up in a sterile environment or whether we used to eat dirt as a toddler. (We now know for example if a baby needs a course of antibiotics in infancy then they are more likely to develop allergies than if they did not have antibiotics at a similar age – and this development of allergies is a learned immune response).
If someone’s innate immune system is compromised then the learned immune system is going to have to try and pick up the slack to protect us. If this goes on for a long time then this will eventually exhaust the learned system and this person will be more likely to get ill more often. You see this in people when they get run down and they’ll come down with glandular fever, or get a cold sore or something similar. More often than not this is not the person catching something new but instead struggling to keep on top of things that are already in their system – until they get to a point that they can’t keep up with it any longer and so they become ill. Essentially their system is just exhausted, and some of these people never fully recover from an illness and develop chronic fatigue or similar conditions essentially because the system is always on high alert and is just worn out.
We now know that someone’s immune system is largely centred around the gut and lymphatic system, in fact 70% of our immune system is comprised of gut-associated lymphoid tissue. We also know that the gut bacteria play an important role in the “training” and the function of the our immune system and they help keep balance. In countries where diet has changed significantly, antibiotic use is high, or the population is chronically stressed then these gut bacteria changes are proposed as a reason for the escalating cases of autoimmune conditions in wealthier countries.
You also have people who have over-reactive immune systems that start responding to things that they never used to such as certain foods. As we know the gut lining is an important part of the the innate immune system and regulates what can travel from our small intestine (where the majority of our food is absorbed) into the blood stream where it is taken around the body to where it is needed. If this gut lining is compromised (increased intestinal permeability or “leaky gut”) then someone’s system will start having to defend against things that should not get into the blood stream in the first place leading to elevated immune responses. This can show up as food sensitivities, mast cell activation, hives, reactions to foods high in histamine etc. The regulation of this intestinal permeability is influenced by diet and by the bacteria in the gut but is also affected by toxins and infections, over-dosed nutrients and some pharmaceutical drugs.
So we can see that there are a number of things that influence your immune system. Simply labelling something as “weak” does not adequately begin to describe what is going on behind the scenes. Some people may be immuno-compromised – but even this does not say which system is compromised, more often people’s innate systems are compromised and their learned system is exhausted.
The good news is that both the innate and learned immune systems can be rebuilt if you can determine the underlying factors that led to the problems. When you do this you can restore normal, healthy immune function and the person can go back to living a normal life rather than worrying about the flu going round.