First, let's go over things that can cause acidity in your body. I listed some common things which all of us know whether we are health practitioners or not.
Saturated/Trans fats:
red meat, overcooked vegetable oils, dairy products
Sugar:
table sugar, other unhealthy "white" carbs like white bread, white rice, white pasta, we all know sweets are not good for teeth!
Drinks:
fully pasteurized juices, sodas, high dose of caffeine, Gatorade type drinks, alcohol
Lack of Oxygen:
improper breathing, lack of exercise, lack of fresh air
Lack of Water Consumption:
water helps with balance, promotes circulation, and just washing/dumping out impurities from within, promotes healthy amount of salivary flow
Lack of Sunlight
the body needs its vitamin D - D for Depression ;), sunlight is also bactericidal
Unnecessary Stress:
an unhealthy amount of stress inhibits proper bodily functions
Lack of Rest
the body cannot regenerate or repair damaged cells without proper rest/sleep
Lack of Application
so you have all this knowledge, will you do something about it? :)
Now, we can talk about things which love and flourish in this acidic environment that you've created in your body and oral cavity.
Harmful Bacteria
Tumor/Cancer Cells
I would say that the above two things are enough reasons to strive for a healthy life style which include healthy eating habits, proper exercise, fresh air, adequate amount of water intake, rest, temperance, and good oral hygiene.
Let's always remember, your mouth is a part of your body! Having a healthy lifestyle will also promote a healthy mouth; a healthy mouth can contribute to a healthy rest of the body. It's become more common knowledge that oral diseases are contributing to systemic diseases like Diabetes, Heart Diseases, Alzheimers, Low birth weight babies, etc. A Neutral-Alkaline pH-environment is highly encouraged!