What I am saying is that, if you eat well, a good balanced diet, not a restrictive one, then you will not need to be concerned about your ph. You can manipulate the ph of your stomach, skin etc by what you eat or use topically, but you cannot manipulate your blood or lymph ph, nor should you be trying too. The body does this perfectly well by itself, and it is just plain dangerous to try and manipulate either.
As we age our stomach acid naturally declines, and as the stomach should be acidic, maintaining this acidity will help with digestive issues, as we get older.
As for a poor diet and lifestyle, the body will maintain the blood and lymph ph level, even if you eat poorly and make poor lifestyle choices. If the body did not regulate these ph levels, you would be dead very quickly.
As for trying to alkalise the parts of the body that should be acidic, why would you bother?? When people drink alkalising drinks this is precisely what they are doing, neutralising the stomach acid, and IMO this is just stupid.