# How solid does fiber need to be for digestion? **URL:** \ **Category:** Factual Questions\ **Created:** [June 10, 2007, 10:17pm UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508 "2007-06-10T22:17:04Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![jackdavinci](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackdavinci/32/3259_2.png) [@jackdavinci](https://boards.straightdope.com/u/jackdavinci)\ **Post date:** [June 10, 2007, 10:17pm UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/1 "2007-06-10T22:17:04Z")
I read an offhand remark somewhere about how liquid diets don’t work and/or cause digestive problems because of the lack of fiber. So I’m wondering: 1. What are the true problems with liquid diets and what are their true causes? 2. How “solid” does fiber have to be to still be beneficial? Store bought fiber supplements are just a powder that you mix with water aren’t they? And I imagine any fibrous food you eat is going to be fairly liquified by the time you are done chewing it and excreting stomach acid on it. 3. In lines with the above, would eating a diet of soup or puree be ok, or would it cause problems? Is there some minimum level of “chunkiness” to the soup or puree that would be nessecary for optimum digestive intake? Fight my ignorance! ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 10, 2007, 10:21pm UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/2 "2007-06-10T22:21:36Z")
Dietary fiber is not fibrous, not does it need to be. Dietary fiber works because during digestion, it absorbs and holds water, making you feel full, and creating a softer, bulkier stool. That is the health benefit. Actual fibers, like rope, are not necessary. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [June 11, 2007, 12:52am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/3 "2007-06-11T00:52:58Z")
Like Fear said. Moreover, the real common powdered fiber supplement is more like mucus or gelatin when it’s in your system, so I wouldn’t call it a solid at all, much less one in the form of fibers. I forget what it’s called but it sounds like “psylosebin” or something - like the hallucinogenic mushrooms (but not exactly the same!). ---
**Author:** ![jackdavinci](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackdavinci/32/3259_2.png) [@jackdavinci](https://boards.straightdope.com/u/jackdavinci)\ **Post date:** [June 11, 2007, 1:30am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/4 "2007-06-11T01:30:08Z")
OK that’s what I thought… but in that case, what’s the real reason liquid diets are bad? And it there any reason you couldn’t live and prosper entirely off of soups and pureés? ---
**Author:** ![Guinastasia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guinastasia/32/5751_2.png) [@Guinastasia](https://boards.straightdope.com/u/Guinastasia)\ **Post date:** [June 11, 2007, 1:31am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/5 "2007-06-11T01:31:19Z")
I thought I read in one of the SD books that if you don’t get enough liquid with fiber, it will back up in your colon as one thick, sticky mess? ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [June 11, 2007, 1:46am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/6 "2007-06-11T01:46:08Z")
[QUOTE=Fear Itself] Dietary fiber is not fibrous, not does it need to be. Dietary fiber works because during digestion, it absorbs and holds water, making you feel full, and creating a softer, bulkier stool. That is the health benefit. Actual fibers, like rope, are not necessary. [/QUOTE] I thought you needed both this form (soluble) fiber, and scrapey stuff to clean out the inside of your intestines and prevent polyps and pockets of infected fecal matter, no? A liquid diet can give you soluble fiber, but not insoluble fiber. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 11, 2007, 1:51am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/7 "2007-06-11T01:51:03Z")
[QUOTE=WhyNot] I thought you needed both this form (soluble) fiber, and scrapey stuff to clean out the inside of your intestines and prevent polyps and pockets of infected fecal matter, no? [/QUOTE] Infected fecal matter? ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [June 11, 2007, 1:59am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/8 "2007-06-11T01:59:00Z")
[QUOTE=Fear Itself] Infected fecal matter? [/QUOTE] y’know, theoretically. Isn’t that where diverticulitis comes from? Fecal matter that gets stuck in little pockets in the intestine and festers and gets infected? It won’t happen to everyone, of course, but I thought that was one of the things we were trying to prevent by increasing fiber intake. I may just be…pardon me…talking out my ass. But I coulda sworn there was an important reason to eat both soluble and insoluble (“scratchy”) fiber. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [June 11, 2007, 2:27am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/9 "2007-06-11T02:27:44Z")
[QUOTE=Napier] Like Fear said. Moreover, the real common powdered fiber supplement is more like mucus or gelatin when it’s in your system, so I wouldn’t call it a solid at all, much less one in the form of fibers. I forget what it’s called but it sounds like “psylosebin” or something - like the hallucinogenic mushrooms (but not exactly the same!). [/QUOTE] [Psyllium](http://en.wikipedia.org/wiki/Psyllium) husk. Metamucil is one preparation using it. There are other things used, such as guar gum (Benefiber). Advertisements for the alternate preparations like to imply that Metamucil, and off brand versions of the same stuff, are horrible and disgusting to take. Ehhh. Not that bad. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 11, 2007, 2:32am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/10 "2007-06-11T02:32:02Z")
[QUOTE=WhyNot] y’know, theoretically. Isn’t that where diverticulitis comes from? [/QUOTE] I will defer to medical professionals, but I don’t think polyps or diverticulitis are caused by a lack of insoluable fiber. [Recent studies](http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=retrieve&db=pubmed&list_uids=9895396&dopt=medline) are even challenging the belief that dietary fiber reduces colon cancer: > [@](#): > > After adjustment for age, established risk factors, and total energy intake, we found no association between the intake of dietary fiber and the risk of colorectal cancer; the relative risk for the highest as compared with the lowest quintile group with respect to fiber intake was 0.95 (95 percent confidence interval, 0.73 to 1.25). No protective effect of dietary fiber was observed when we omitted, adjustment for total energy intake, when events during the first six years of follow-up were excluded, or when we excluded women who altered their fiber intake during the follow-up period. No significant association between fiber intake and the risk of colorectal adenoma was found. ---
**Author:** ![Erati](https://avatars.discourse-cdn.com/v4/letter/e/8491ac/32.png) [@Erati](https://boards.straightdope.com/u/Erati)\ **Post date:** [June 11, 2007, 3:58am UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/11 "2007-06-11T03:58:50Z")
[QUOTE=jackdavinci] OK that’s what I thought… but in that case, what’s the real reason liquid diets are bad? And it there any reason you couldn’t live and prosper entirely off of soups and pureés? [/QUOTE] If I remember correctly, I once read an article in “Nutrition Action Healthletter” by the Center for Science in the Public Interest that humans evolved to eat a fairly solid food diet, and that a liquid-only alternative would leave one with the discomfort of constant hunger. ---
**Author:** ![jackdavinci](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackdavinci/32/3259_2.png) [@jackdavinci](https://boards.straightdope.com/u/jackdavinci)\ **Post date:** [June 11, 2007, 5:48pm UTC](https://boards.straightdope.com/t/how-solid-does-fiber-need-to-be-for-digestion/407508/12 "2007-06-11T17:48:07Z")
[QUOTE=Erati] humans evolved to eat a fairly solid food diet, and that a liquid-only alternative would leave one with the discomfort of constant hunger. [/QUOTE] Ok… so how “solid” does food have to be at minimum, and how can the body tell the difference between food that starts out less than solid vs food that starts out solid but is chewed and then dissolved by stomach acid?