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Acid/Base PRAL Questions

I’m sure JB can answer this, but others might know.

I was trying to explain this idea to a friend of mine but started getting confused when I reached citrus fruits and soda. The items are acidic, yet the PRAL score is basic. How does that work? Is there a difference between the PH of the food measured outside the body vs. the renal acid load??

There are different definitions of acid and base (Lewis, Bronsted-Lowrey etc) and it gets all the more complicated in biochemical situations. In a nutshell the acidic or basic properties of the food you eat are down to the mineral ions (in this instance), not really the H+ or OH- you usually see in acid alkali chemistry. These acid and basic properties of the food you eat are not apparent until they are metabolised and the acid/base chemical properties of the foods are unlocked.

For example lemon juice tastes sour as it’s an organic acid. It contains three groups called carboxyl groups, which will readily react in an acidic fashion (due to H+ ions breaking off the carboxyl group) so the acidity is readily apparent or ‘at the surface’ if you will. That acidicty is dealt with long before it reaches the kidneys. Remeber the stomach is a bag of acid.

The acidity in meat is hidden on the other hand, its physiologically acidic properties are locked away in the structure of the tissues. As it’s digested, utilised by the body then eliminated from the cell as waste, then the acidic properties come out of the woodwork and have to be dealt with.

Okay, very interesting. I figured it had to be something like that. Boy it’s been awhile since I’ve had chemistry.

So most of the time when someone says soda or orange juice is acidic they’re really only refering to it’s effects on the mouth and stomach. Once it reaches the kidneys and they’re broken down to their mineral components they may be basic in the blood?

Thanks for clearing that up.

Ah, but fizzy drinks quite often contain phosphoric acid. Bad bad bad. This defo falls into the acid load side of things as it’s a cation.

Good job on fielding that one drewsky. Another important point to remember as explained to me by a biochemist is that your body wants everything to be as close to alkaline as possible by the time it is done digesting it. In the case of soda it will throw buffers at it like crazy in an attempt to neutralize it. This is why the PRAL score is dramatically higher than most people think it would be. It still takes a toll on the body though.