What could be so bad about a harmless water product? Most bottled waters are not from springs or good sources, they're actually mainly made from tap water. If you're lucky, its a filtered tap water that you're getting. Better off getting a water filter in your house than buying loads of plasticized bottled water. Now lets move on to some other things we should avoid when seeking to upgrade our immune system.
With the obvious set aside (fast food, anything processed, packaged, made from corporate companies), there are many other things that people may be missing. For example, many people do not get a good night's sleep. This is a precursor to damaging your immune system in the long haul. So many people cut themselves short by messing with their circadian rhythm. While work and other worldly factors may limit our quality or quantity of sleep desired, things like staying up late to watch TV are not helpful factors.
Another thing that gets people is their "healthful diet". Many people exclude many healthy foods from their diet (such as raw dairy products) in a means to "become healthier". This is only starving the immune system's need for the wide-spectrum of nutrition that it requires. A good example is how people think that they are somehow synthesizing B-12 in their gastrointestinal tract. This has never been shown to be true either scientifically or by personal experience so I would not recommend trying it. In other words, if you are a vegan interested in health rather than dogma, I would highly advise looking into raw sustainable local dairy products to add to the diet. This recommendation strains from seeing so many vegans with terribly weak immune systems. A lot of vegans are not health conscious at all and sacrifice themselves instead of the animals.
Now that we've covered the importance of a healthy balanced diet, lets look into the herbal pharmacopeia and how it can help us to develop stronger immune systems. There are many classes of herbs, so the main ones that we will cover are the tonic herbs. We will not go much into the "power class" of herbs such as echinacea, goldenseal, osho, usnea, bee propolis, or oregon grape root/barberry/berbine class alkaloids as these are potent medicines that should be used on an as needed basis. So many people take echinacea every day in order to strengthen their immune system. This, however is a terrible mistake and will not do the individual any good.
So what are the tonic herbs? Tonic herbs would include a class of herbs that are safe to take on an ongoing basis, that is, we cannot max out on them or overdose by taking them every day. They basically "feed" our immune system. Some great tonic herbs would include: astragalus, green tea (organic, high grade), wild reishi, wild medicinal mushrooms in general (chaga, cordyceps, agaricus, turkey tail, etc.), goji berries, eluethero (aka Siberian ginseng), cat's claw (uno de gato), pau d' arco, licorice root (caution advised for people with high blood pressure or edema), cannabis indica (check out the endocannabinoid system that our body requires to function on every level)*. The best immunomodulators would include cat's claw & cannabis. Seriously, who knew that the immune system ran off of cannabinoids?* By the way, if you are against the pharmaceutical companies and for natural alternatives, then you really need to team up with the hemp plant against Big Pharma. The hemp plant has been one of the leading causes of drug companies to wage a long war against natural remedies because of its wide range effectiveness and availability. If we could grow our own medicine in our back yard, this would not make a good profit for the pharmaceutical companies would it?
Other important factors to look into when upgrading our immune system is our stress levels, exercise habits, hormones, EMF exposure, and other sources of exogenous chemical exposure (fluoride, chlorine, MSG, trans fats, aspartame, etc.) The goal is to fortify our bodies with as much natural substances as possible, the less processed food we eat and the more our food/medicine comes closer from the Earth, the healthier & happier we will be. May unlimited health be yours.