Can only eating processed food and bottled water reduce your immunity?

To the first question, my guess is that yes, you have lost some kind of immunity, but the reasons of this lost may not only lay on your habit of avoiding raw food, and tap water, but in the practices of all the Western culture.
I do not know how to quote properly, but here it is something I found in an article in the New York Times Magazine (May 15 2013):

A handful of microbiologists have begun sounding the alarm about our civilization’s unwitting destruction of the human microbiome and its consequences. Important microbial species may have already gone extintc before we have had the chance to learn who they are or what they do. What we think of as an interior wilderness may in fact be nothing of the kind, having long ago been reshaped by unconcious human actions. Taking the ecological methaphor further, the “Westernized microbiome” most of us now carry around is in fact an artifact of civilization, no more a wilderness today than, say, the New Jersey Meadowlands

The title of the article is”Some of my best friends are germs”, by Michael Pollan.

The next paragraph of the one I just quoted says:

To obtain a clearer sense of what has been lost María Gloria Dominguez-Bello, a Venezuelan born microbiologist at New York University, has been traveling to remote corners of the Amazon to collect samples of hunter-gatherers who have had little previous contact with Westerners or Western medicine “We want to see how the human microbiota looks before antibiotics, before processed food, before modern birth”, she told me. “These samples are really gold”.

So, my guess is that not only you, who, I assume, are a Westerner, but a lot of us who live in the Western world, or in places who have the same practices , have a less strong immune system, because of the practices our culture has.

Take this, as an example, also, from the article I cited before:

One bacterium commonly found in the non Wester microbiome, but nearly extinct in ours is a corkscrew-shaped inhabitant of the stomach by the name of Helicobacter pylori. Dominguez-Bello’s husband, Martin Blaser, a physician and microbiologist at the N.Y.U., has been styding H. pylori since the mid 1980s and is convinced that it is an endangered species, the extinction of which we may someday rue. According to the “missing microbiota hipothesis,” we depend on microbes like H. pylori, to regulate various metabolic and immune functions, and their disapearance is dissordering those systems. The lose is cumulative: “Each generation is passing on fewer of these microbes,” Blaser told me, with the result that the Western microbiome is progressively being impoverished.

The article is very interesting and informative.

The answer to the second question, I guess is yes, for the same reasons mentioned in the last sentence I quoted.

Of course, when you, or me, travel, we are at risk. Our immune system, may not respond properly to the microbes found in the new environment. But I believe, this apply also in the opposite sense. We may carry diseases for which the native people’s immune system is not properly armed to fight.

The tap water in Taiwan isn’t clean as in US, people often boil the water first to drink, mostly to avoid the worms and diseases. Brushing teeth or ordinary uses is fair enough to use tap water.

I think you shouldn’t try raw food since these dishes aren’t clean, even Taiwan people sometimes get sick for eating raw foods.
https://halong-bay-cruise.com

If you don’t live in a glass house, don’t worry about your immune system’s getting weak since the air has contained enough bacteria for your body to resist

You should avoid raw meats.
Sea food fresh under cooked is very bad. You can get flukes from it. Both liver & kidney. They are easy to treat in the early stages.
Water you need know location. Much is just filtered & treated tap water. The big thing here is minerals in the water. Lead arsenic etc. Well water even treated can be bad. Even boiling will not remove arsenic or lead.

Next how is your small intestine?
Look at it as a storage area for bacteria. The more you travel the more different ones you have there in storage. They are released as needed in each area you travel. Stored when not needed. Why world travelers become immune to local food much more so than newbe’s.
We have the bacteria need in storage.
You need develop it for each new area you are in.

So enjoy.
Travel, build imunety you do not have.

If in areas were well water is drank. Bring a clear jug. Get your water set in sunlight for 2 hours. It is now about as safe as bottled water. except minerals. Add a few drops of bleach. You now have treated water. Let settle or boil if you wish some minerals to settle from the water.

I think I need to answer this question on multiple levels.

1. Sorry to say so but you have succumbed to a series of urban myths. Neither is drinking tap water or eating raw food in Taiwan a threat to your health, nor is eating “processed food” (the term is meaningless from a scientifc or medical perspective ).
2. Tap water is safe in pretty much every civilized country. Since disinfectant agents and regular scanning for bacteria have become commonplace hygienic problems related to tap water have become very very rare. In fact more people catch bacteria from taking showers than from drinking tap water. Why? The hot water boiler, when poorly maintained and run at too low temperatures can become a breeding ground for bateria. So are air-conditions systems. I therefore recommend to not use the airconditioning and avoid showering in Taiwan.
3. Eating raw and not perfectly hygienic food is not a health risk (except for some food and countries with specifics parasites). When you chance to a different country, in a different climate zone and diferent types of food the bacteria in your gut will eventually adapt to the change in circumstances. That is diffrent strains of bacteria will settle in. This can temporarily cause diary but after a few days you will be just fine. You can delay but not avoid this effect.
4. One aspect of the narrative is largely true, although the science behind it is a bit convoluted. When you always eat cooked food, disinfect your hands, avoid dirt etc. you will not ingest gut bacteria and the eco-systems in your guts will be, lets say, “underdeveloped”. Note that gut bacteria are not only harmless but neccessary for your body to function properly. This effect has been suspected for a long time, but could only be quantified with genetic analysis techniques in the last few years. E.g Native people living in natural environment have ~2x the variety in gut bacteria than the average civilized person. It has also been proven that certain types of gut bacteria contribute to the regulation of our immune system.

So in short the recommendation is: “eat some shit” :-). In more scientific terms: Your paranoia of avoiding unhygienic food and tap water indeed has a chance of creating a deficient intestinal flora, which could potentially impair your immune systeme. But worst of all, you are missing out on a lot of fun Taiwan.

This article suggests that it can. Children from Finnish Karelia and Russian Karelia were observed, similar with regards to genetics but former leading much more urbanized life style. It turns out they have much greater incidence of autoimmune diseases.

However, you better start imunnizing yourself while young. I’m not sure that making a U turn in this regard is safe. Better change your habits slowly.