Ok, so there are two pH values that people talk about.

The first is the pH of the body's interstitial fluids. That means the ~30% of the body's fluid volume that is not inside of cells, but that is inside the body. (Remember, an object in the GI tract is not inside the body. In order to enter the body, a particle has to cross at least once cell membrane.) The interstitial fluid includes the blood's plasma (the liquid component of the blood), and the fluids that bathe the cells. In general, the cerebrospinal fluid and the fluid within the inner ear is not considered part of the interstitium.

This fluid compartment's pH is slightly alkaline, with a value between 7.35 and 7.45 (the "normal" range varies depending on the center, but at UofMichigan Hospital, that's the "normal" range). Very powerful physiologic mechanisms exist to maintain this pH and there is cross-talk between the kidneys and lungs to maintain this. Even patients with severe pulmonary or renal disease tend to stay in this range.

If you get out of this range, you have either an acidemia or an alkalemia. Patients with either condition are typically very sick. I don't mean subtle aches and pains; I mean ICU sick.

The idea that one could change this pH by diet is pure nonsense and I would urge anyone to avoid any practicioner claiming otherwise. You can down very acidic or alkaline foods and your kidneys will simply respond by either excreting more bicarbonate (to lower the pH if you eat a lot of alkaline) or by excreting more hydrogen ion (to raise the pH if you eat a lot of acidic food). You can change your urine's pH with diet (which is why cranberry juice helps prevent UTI's), but not your internal pH.

The other pH that people talk about is the stomach's pH. In a normal stomach, this is a very acidic pH of roughly 1-2. This pH can be changed with foods, depending on what you throw into your stomach. But again, the stomach does have power physiologic mechanisms to keep the pH low. You can use some drugs like proton pump inhibitors to raise the pH of the stomach. There is controversy as to whether alkaline foods have much of a lasting effect on stomach pH and there seems to be a lot of individual variation. The general consensus among gastroenterologists that I've asked about this is that "no," the only way to change the pH in the stomach is with a proton pump inhibitor (like omeprazole/'PRILOSEC') or a histamine H2 blocker (like ranitidine/'ZANTAC').

However, I also respect that people have different health beliefs and I know that I've benefited from therapies that are not approved by Western medicine. However, I will reiterate that you do not want to even try to mess with your internal pH. You're wasting time and monety doing so, but if you actually succeed, prepare for a very long hospital stay.

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-Mike
Certified Mad Doctor (in training)

___________________________________________ -Mike Certified Mad Doctor