How does the pH of the contents of the gut vary from the stomach to the anus? I know that chyme is very acidic, but after that?

1 Answer 1


Not sure if I answered this right:


The system begins in the mouth, where the pH of saliva is 5.7 – 7.0. In the esophagus the pH is 7.0. The stomach pH is 1.5 – 3.0. In the Duodenum (upper part of the small intestine) pH is 4.0 – 5.0, and in the lower part of the small intestine (jejunum and ileum), pH 6.5 – 7.5

The reason for it:


In order to carry out their individual functions, each section of the digestive system maintains a pH that suits the needs of the environment. The first part of the system prepares the food for digestion. This section’s weak acidic surroundings begin the process. The second area, the stomach, must supply enough acid to break the food into its nutrients. However, when the food continues into the intestines, it no longer needs acid. Both intestines bring the matter closer to the pH of the body

Basically these values stay consistent with some minor changes, unless a person is experiencing a acid-base imbalance. These are life threatening and can be extremes in acid or alkaline. The pH as you can see stays within the range it needs to be, in order to process food.

  • Good answer but I sure wish you could find a more definitive source for the PH numbers. Leaflady doesn't state where they got those numbers.
    – Carey Gregory
    Feb 3, 2016 at 5:07
  • 2
    I made a minor edit (I hope that you don't mind, but you can always roll back to the original version if you do), because you wrote yourself that pH fluctuates in all parts of the GIT. A further reference that you might use: gut.bmj.com/content/30/5/573.abstract. The only part I slightly disagree with is the part about acid-base imbalance: the 'allowed' range of the pH in blood is far more narrow than that in the GIT, hence gut and stomach pH fluctuations will be higher than those in blood. For acidosis/alkalosis, the kidneys and lungs are the organs that compensate, not GIT. Overall +1
    – Lucky
    Feb 3, 2016 at 8:48
  • I would expect the product of an ileostomy (called what?) to be neutral-ish. Why, then, is it so acidic that it attacks the skin?
    – Justin
    Feb 23, 2016 at 22:48
  • 1
    @Justin I'd have to research that. But I'm not sure about that. It might be..........
    – Pobrecita
    Feb 24, 2016 at 16:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.