After many years of a pretty crap immune system, I have had a pretty good run in the last two or three years, with few colds or afflictions. I have also been eating low-carb, and progressively more primal for around 8 months. In the last two months, I'd say I am sticking to the diet 80-90% of the time, if you include dairy and coffee, which I do. And yet I have been sick for about 3 weeks - from sinus infection, to a cold, to cystitis. What's going on? I have been pretty busy/stressed - is that maybe undoing all my good dietary work? Has anyone else experienced long, low-level illness on the diet?
The ideal of a perfectly functioning immune system that can prevent any illness is simply not possible in reality. Sure being healthy can increase your resistance but no diet or anything else can make you invulnerable. Stress does not help though.
Our immune systems have been involved in an evolutionary arms race with infections for our entire existence and it is not one we can win as microbes can always evolve faster than we can. Disease causing microbes can find ways around the strongest immune system. For example in the influenza pandemic of 1918, young people with the strongest immune systems were most likely to die. Isolated hunter-gatherer communities have often been some of the hardest hit by such infectious diseases. An example is the Alaskan Eskimo communities, many of which were decimated by the 1918 flu and also by infections like measles on first contact with Europeans. http://arcticcircle.uconn.edu/HistoryCulture/Sickness/sickness.html
In your case it is likely that you picked up the sinus infection first and then the resulting damage and inflammation gave the cold virus an easy entry. The combination of infections will occupy your immune system enough to give the cystitis an opportunity.
I suppose my point is that you shouldn't be hard on yourself for getting sick, I doubt that a 100% primal or paleo diet or even a stress free life would have prevented them. You are likely to get over the illness and then have another period free of infections.
An interesting additional point is that a certain percentage of people can have no symptoms when infected with a cold virus. These are the people who never appear to catch common colds while happily spreading them to everyone else.
I would refer you to Dr Art Ayers blog at http://coolinginflammation.blogspot.com/
He has pretty well proved to me that a fully functioning gut flora is the key to a long healthy life without any sickness. When gut flora is functioning well, the body's immune system is at its peak.
It has taken me a long time to reach this conclusion. It makes sense to me because the body is pretty much perfect when we are born. We then inundate it with neolithic foods that the body was never designed to handle..particularly baby forumula which really fouls up the babys immune system and this lack of a good immune system manifests itself by all the problems formula fed babies have and then we innundate our guts with refined wheat products and huge amounts of sugar...and each body reacts differently...ie allergies, asthma, acne, excema...etc. It is basically garbage in, garbage out.
I have incorporated into my diet most of his suggestions such as eating burdock root, chicory, jeruseleum artichokes, artichokes, pectin, inulin, leaks, onions...which are called polysaccharides. These foods ferment in the gut to build healthy gut flora.
Taking any antibiotic kills the bacterial cells in the gut, thus compromising the immune system.
Stress causes imflammation and compromises the immune system.
Roam around Dr Ayres' blog and see if you come to the same conclusion.
Also see this post on paleohacks for more: http://paleohacks.com/questions/3813/jerusalem-artichokes-good-or-bad