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Significance of pH in digestion[edit]

Very confusing or wrong : "The mucosal tissue of the small intestines is alkaline with a pH of about 8.5." From many other source it said that the small intestine content is slightly acid (makes very much sens compared to the more basic environment at the end), so if the content is acid I don't know how and why the mucosal tissue could have an instant Ph jump of 1,5 !!!! Anyway a clear difference should be made between the content Ph and the intestine walls ph, and it's variation within the walls.

Things to Add[edit]

Digestive Molecules

This site talks about how digestion is affected by the circadian rythm. It would be also good to address this notion of how digestion makes you sleepy. Lot of people think that tryptophan is only in turkey, but it also present in other foods.

The serotoninergic system is known to modulate mood, emotion, sleep, and appetite and thus is implicated in the control of numerous behavioural and physiological functions. Decreased serotoninergic neurotransmission has been proposed to play a key role in the aetiology of depression.

The graph on the left shows how alertness varies through out the day in relation to the three circadian phase regulatory as molecules. Serotonin and SAM both start off in relatively high concentrations in the height of the day, while melatonin is almost no where to be found. As the sun begins to set, the pineal gland recognizes that there is less and less light. Norepinephrine begins to bind to β-receptors in the pineal gland, and the pineal gland used the day time store of SAM and serotonin to manufacture melatonin Understandably, while melatonin concentrations rise, SAM and serotonin concentrations fall. Once the concentration of SAM is to low to make any more melatonin, melatonin levels start to drop off, and SAM is free to rebuild. When the pineal gland senses the coming of light, SAM is produced again starting a new daily cycle. The graph on the right is almost identical to the one on the left. The difference is that sleepiness is show as the affect on the mammal instead of alertness. The purpose of having two graphs was to show that high melatonin levels correspond to feelings of sleepiness, while high serotonin and SAM levels correspond to high levels of alertness.

Even though you get energy from food, it also takes a lot of energy to DIGEST food so your body can use it. Energy use is called METABOLISM. When you eat, the rate of your metabolism goes up because of all that digestive activity in your gastrointestinal tract. (That's basically everything from your mouth to your anus.) So if you need energy to digest your food, it makes sense that there's LESS energy available for the REST of your body.


Finally, when you eat some foods--mainly carbohydrates--the level of "tryptophan," an amino acid in your blood, increases. Tryptophan is converted into "serotonin" in the brain. And guess what serotonin does. It makes you sleepy!

This last point is addressed in the tryptophan article. Maybe simply add a link then? --Moo 03:27, 24 June 2006 (UTC)

Large intestine[edit]

What is the precise role of the large intestine in the process of digestion? --LostLeviathan 23:53, 18 Apr 2005 (UTC)

Possible copyvio[edit]

This very large and detailed edit [1] may be a copyright violation. The editor will only divulge that the source is "online" and has made numerous similar edits that are copyright violations. I recommend removing all that remains of this edit: Carbohydrate Digestion Discussion and Fat Digestion. Fat Digestion has been heavily vandalized which is why much is nonsensical. --Ronz 16:36, 19 October 2006 (UTC)

Just to be clear, I removed the information in question November 20. --Ronz 02:45, 9 December 2006 (UTC)


It might help to rearange the digestive process section to make it easier to read and more logically laid out.

Stages of protein digestion would be good to add, along with the fat digestion.

Esophagus vs Oesophagus[edit]

The spelling of this word in the article is inconsistent. I believe the word with an "o" is British, while the one with just an "e" is American. I'm Canadian and I don't know (or care) which one we use. Does Wikipedia have a policy in cases like this? If so, someone please apply it. Baribeau 02:36, 18 April 2007 (UTC)

man....... I just editted it to oesphagus (im from UK, and technically we invented the word so lets just keep it that way :P)

SeeWP:ENGVAR. --Ronz 00:23, 30 April 2007 (UTC)
esophagus feces --Ronz 21:29, 10 May 2007 (UTC)

And to save anyone else checking, the original usage in this article had the American spelling, so that stands. Dbfirs 07:16, 12 June 2008 (UTC)

Actually, the original article used "oesophagus". So this article should use the international spelling: (talk) 13:08, 7 April 2009 (UTC)
I am aware of the policy, and recognize that this is an old issue, but it simply seems silly that the spelling used here is Oesophagus, which redirects to Esophagus. It would be nice to see some cross-article consistency in addition to internal consistency. JoeSperrazza (talk) 01:37, 20 June 2010 (UTC)

Strong Acid/Base[edit]

It's always been my understanding that a "strong" acid or base is one that completely dissociates in aqueous solution, yet in the article it defines it as an acid less than 5 in pH or a base greater than 8 in pH. Then in the 2 paragraphs later it says the small intestine is "weakly alkaline" at a pH of 8.5. Please, could someone more knowledgeable on the digestion tract than me make this segment comprehensible? —Preceding unsigned comment added by (talkcontribs)

Stomach section[edit]

Changed to remove the false implication that Hydrochloric acid is an enzyme. David 13:44, 10 September 2007 (UTC)

This section and the section on gastric phase seems poorly written. A decrease (lowering) of pH is an increase of acidity, the stomach is normally around a pH of 1-3, the body/brain controls the amount of HCl secreted into the stomach. Parts of this article totally misstate this. Also, it is my understanding that acetylcholine is a neurotransmitter and only controls the amount of peristaltic activity not secretion of gastric acids. Could someone comment?Ecogreg2009 (talk) 17:33, 23 February 2009 (UTC)


The article's definition of the term says: "Digestion is the breaking down of food in the body, into a form that can be absorbed. It is also the process by which the body breaks down food into smaller components that can be absorbed by the blood stream." I don't really understand this. To me, it sounds like the article defines two different meanings of the word - but are they not exactly the same? // habj (talk) 09:16, 17 August 2008 (UTC)

the easier version is the process by which food is broken down into simpler soluble substances by enzymes for absorbtion

Phases of gastric secretion[edit]

Overall this seems to be confusing and inaccurate. The original portion of the gastric phase misstate pH in stomach, said gastric acid increased pH, increase in acidic level is reflected by a decrease(lower pH number). The normal pH of a human stomach is 1-3 dependent on different types of food and quantity. Also I have never seen any literature that acetylcholine and histamine triggers secretion of HCl. References please.Ecogreg2009 (talk) 17:42, 23 February 2009 (UTC)

why is digestion important to our life?[edit]

what does digestion do for us? —Preceding unsigned comment added by (talk) 03:57, 18 April 2009 (UTC)


I was never taught that bile does anything other than emulsify fat.

If indeed it goes beyond this common knowledge, IMHO it should be cited. (talk) 05:23, 30 May 2009 (UTC)

Incorrect information on article[edit]

The article states the following:

"As protein enters the stomach, it BINDS to hydrogen ions, which LOWERS the pH of the stomach to around pH 1-3."

The information on the sentence above is incorrect. If anything binds to hydrogen ions, the environment becomes more alkaline, therefore the pH rises and not lowers. Acidity increases as the number of hydrogen ions in a given environment increase. —Preceding unsigned comment added by (talk) 11:07, 30 May 2009 (UTC)

Also, the current published article says "Food enters the ear". It has been fixed, but the change has not been approved? —Preceding unsigned comment added by (talk) 17:18, 21 November 2009 (UTC)

Energy conversion efficiency of (human) digestion[edit]

Output energy is always lower than input energy

The human digestive system is one of many things, like light bulbs and steam engines, that have an input (from the mouth into the stomach) and a smaller output (from the small intestine into the blood).

The loss seems to be quite big, as anaerobic digestion of excrements is an economic way to get energy. Does anyone know the energy conversion efficiency of the human digestive system? It's a machine, created by the evolution for some purpose - so the question is legitimate, and the answer could be given in the article.

My question in different terms: If we replaced human digestion by parenteral nutrition - how much farming could we spare? Greetings, Lipedia (talk) 19:47, 28 July 2009 (UTC)

Role of acidity - contradictions[edit]

There is a contradiction between parts of this page. The "Stomach" section says that:

"Food enters the stomach through the cardiac orifice where it is further broken apart and thoroughly mixed with gastric acid, pepsin and other digestive enzymes to break down proteins. The enzymes in the stomach also have an optimum, meaning that they work at a specific pH and temperature better than any others. The acid itself does not break down food molecules, rather it provides an optimum pH for the reaction of the enzyme pepsin"

Later, in the "Significance of pH in digestion" section, the following is stated:

"Most digestive enzymes are sensitive to pH and will not function in a low-pH environment like the stomach." and later "In the small intestines, the duodenum provides critical pH balancing to activate digestive enzymes"

pH activates pepsin only, or other digestive enzimes as well? what enzimes require low pH, what require neutral? Clarification needed. —Preceding unsigned comment added by (talk) 12:16, 25 November 2009 (UTC)

Removed minor vandalism "santosh neupane wrote tish" (talk) 15:49, 18 April 2010 (UTC)

"Invitation to edit" trial[edit]

It has been proposed at Wikipedia talk:Invitation to edit that, because of the relatively high number of IP editors attracted to Digestion, it form part of a one month trial of a strategy aimed at improving the quality of new editors' contributions to health-related articles. It would involve placing this:

You can edit this page. Click here to find out how.

at the top of the article, linking to this mini-tutorial about MEDRS sourcing, citing and content, as well as basic procedures, and links to help pages. Your comments regarding the strategy are invited at the project talk page, and comments here, regarding the appropriateness of trialling it on this article, would be appreciated. Anthony (talk) 11:55, 31 August 2010 (UTC)

The list of articles for the trial is being reconsidered, in light of feedback from editors, and should be ready in a day or two. If you have any thoughts about the Invitation to edit proposal, they would be very welcome at the project talk page. Anthony (talk) 14:41, 2 September 2010 (UTC)

Bacterial secretion sections are too specialised[edit]

This is a very uneven article in its academic level. It should be a general overview of the biological principles of digestion. I think 99% of the readers coming here will want information on digestion in eukaryotes. The sections on bacteria under Secretion systems should be moved to a specialised article. The schematic drawing of bacterial conjugation looks out of place, particularly as the first illustration in an article on digestion. What would be more interesting and relevant regarding bacteria would be their role in digestion in multicellular animals. Strayan (talk) 05:42, 20 August 2012 (UTC)

Agreed.--Taylornate (talk) 06:06, 20 August 2012 (UTC)
I think the whole section is out of place. It deals mainly with secretion in bacteria, not with digestion. Only the secretion of enzymes to digest external macromolecules to yield small molecules used for bacterial nutrition should be treated, but here a number of types of secretion not related with digestion are treated. Also, again the image is not related with digestion.--Miguelferig (talk) 23:19, 7 August 2013 (UTC)
The section on bacterial conjugation, as well as the illustration should go. They're not part of any digestive processes.Wzrd1 (talk) 23:26, 7 August 2013 (UTC)


Grammar needs to be fixed. Xzaviur (talk) 21:07, 15 December 2012 (UTC) Xzaviur

If you can be more specific about what you would like to see changed, I'm sure someone can help edit the article accordingly. -- Ed (Edgar181) 21:40, 15 December 2012 (UTC)

Semi-protected edit request on 11 March 2014[edit]

The start of the article on digestion has a redirect from the term Gastrointestinal tract which then adds its own redirect using the text 'For digestion in humans specifically, see Human gastrointestinal tract.' However the article on the Human gastrointestinal tract. does not deal with digestion instead focussing on the gross anatomy of the GI tract. Meanwhile the most specialized section of wikipedia on 'digestion in humans' is actually a subsection of the original digestion article in particular section 3 'human digestion process'... I would suggest the redirect to 'Human gastrointestinal tract' from this page either be removed or reworded. (talk) 03:55, 11 March 2014 (UTC)

Done Reworded it into the leading paragraph for that section. Thanks. Cannolis (talk) 04:21, 11 March 2014 (UTC)

Text about animal gut use moved to Gut (anatomy)[edit]

Section about animal gut use has been moved from here to the Gut (anatomy) page. -Ugog Nizdast (talk) 12:11, 25 February 2015 (UTC)