Most of the information about body Ph and its effect on health, is somewhat questionable or misleading, and probably only relates to people who eat large amounts of grains and other non paleo foods.
Basically what I believe,
Acid forming foods when eaten in excess by people who are already on the verge of being deficient or are somehow unbalanced in minerals, could have some negative effects, if the body doesn't have the mineral reserves to properly neutralize the corrosive elements produced by the body through the digestive proccess.
By far the most damaging foods are grains and other high carbohydrate starches that may not initially be acidic, but there is acidic metabolic waste that is produced by the body as a result of digesting those types of foods, that can cause the body to have to leach minerals in the neutralization possess in order to maintain proper PH.
Some acidic fruits and vegetables can actually have a positive effect on the bodies PH, by keeping the guts PH properly balanced. After eating an acidic food such as a tomato or some other fruit, the gut itself wont have to produce as much of its own acids for digestion, and so wont have to leach its own minerals in the digestive possess.
( this is just my new theory, haven't really studied it too much, but my intuition tells me it seem reasonable)
