# If humans could digest cellulose ...
**URL:** https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298
**Category:** In My Humble Opinion
**Created:** [September 7, 2015, 9:56pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298 "2015-09-07T21:56:28Z")
**Posts on this page:** 14
**Page:** 2
### Author:  [@Senegoid](https://boards.straightdope.com/u/Senegoid)
#### Post date: [September 8, 2015, 3:51am UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/21 "2015-09-08T03:51:58Z")
> [@CCitizen](#):
>
> \>\> Diogenes?
>
> Thanks – I will look him up.
There were several historical Diogeneses. You’re looking for Diogenes of Sinope, also known as Diogenes the Cynic. (Formerly a poster here too, but got banned a few years ago.)
ETA: You’ve probably seen the famous trope, an image or drawing of an ancient toga-clad Greek carrying a lantern. [_That_ Diogenes.](http://www.thefamouspeople.com/profiles/diogenes-of-sinope-224.php)
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### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [September 8, 2015, 4:10am UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/22 "2015-09-08T04:10:17Z")
> [@CCitizen](#):
>
> What was the name of ancient Greek philosopher who speculated about the possibility of people not needing food but being able to satisfy their hunger by looking at food and rubbing their stomach?
Diogenes’ line actually was:
> [@](#):
>
> When scolded for masturbating in public, he said “I wish it were as easy to banish hunger by rubbing my belly.”
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### Author:  [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)
#### Post date: [September 8, 2015, 4:12am UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/23 "2015-09-08T04:12:36Z")
> [@Scumpup](#):
>
> The job market for dentists would explode if you are imagining people actually consuming grass. Even cooked, grass is tough and abrasive and will require a lot of chewing. Human teeth would wear out fairly early in life on such a diet. Better to finely mill the cellulose material and mix it in with other foodstuffs as an extender.
[Or blend it up into a liquid and sell it to gullible people as some kind of supernutrient juice.](http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/wheatgrass/faq-20058018)
I do have to wonder whether the o.p. has ever been in a cattle yard or feedlot. This idea might seem desireable on an individual level from a totally naive standpoint but beocmes untenible even as a concept once you consider the, uh, downstream implications of sucha diet. (To be fair, there are ruminants that are not as utterly disgusting in terms of fecal output as cows and sheep, but they’re even less efficient at processing grass or most leaves into free glucose.) And at a basic metabolic level, we need more than glucose; there are essential vitamins we would have to be able to extract or synthesize, and of course the essential amino acids which humans cannot synthesize. While all of these can be provided by some combination of vegetable matter (in particular, certain legumes) they are not going to be provided by grasses and leaves in sufficient density.
It would literally be easier to make human beings able to be sustained on a diet of processed sewage than to digest cellulose as the primary metabolic fuel.
Stranger
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### Author:  [@bump](https://boards.straightdope.com/u/bump)
#### Post date: [September 8, 2015, 4:33am UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/24 "2015-09-08T04:33:33Z")
Well, if some bacteria was going to help humans eat cellulose to the point where we wouldn’t need specific complex carbohydrates in our diet (I’m assuming that’s the point- we’d still need fats, proteins and vitamins), that would help with world hunger, as far as few people would _need_ to starve, since they could just go eat some old newspapers or something like that to sustain themselves.
The bigger implication is that we’d have a ready-made biofuel bacteria; any kind of bacteria able to let humans eat cellulose with our current digestive systems would pretty much be something that would be able to change cellulose to sugar really quickly and completely, and that would be immensely useful for fermenting cellulose into ethanol for motor fuel.
So while it might be good for people in extremis (who’s going to eat sawdust or an old cotton sheet by choice), it would be really helpful in getting the world away from petroleum.
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### Author:  [@Patty\_O\_Furniture](https://boards.straightdope.com/u/Patty_O_Furniture)
#### Post date: [September 8, 2015, 3:15pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/25 "2015-09-08T15:15:00Z")
Monsanto would engineer GMO grass and succulent bamboo that melts in your mouth.
The villain in Die Hard XXVII threatens the entire population of Eugene, Oregon with starvation by spraying its forests with Amoxicillin.
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### Author:  [@Surreal](https://boards.straightdope.com/u/Surreal)
#### Post date: [September 8, 2015, 4:44pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/26 "2015-09-08T16:44:15Z")
> [@Saint\_Cad](#):
>
> As a scientist I invent a bacteria that can live in the human gut and process cellulose for us. Yay! No more world hunger as everyone can eat grass and get glucose from it. I spray it all over the world so eventually everyone will have this bacteria in their system.
This really isn’t that far-fetched as people in some nonindustrial societies have been found to have special intestinal flora that can ferment cellulose into short-chain fatty acids.
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### Author:  [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)
#### Post date: [September 8, 2015, 4:45pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/27 "2015-09-08T16:45:52Z")
And people complain about there being sawdust in fast-food hamburgers _now…_
Unintended result: Lots fewer trees.
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### Author:  [@penultima\_thule](https://boards.straightdope.com/u/penultima_thule)
#### Post date: [September 9, 2015, 4:08am UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/28 "2015-09-09T04:08:55Z")
> [@Surreal](#):
>
> This really isn’t that far-fetched as people in some nonindustrial societies have been found to have special intestinal flora that can ferment cellulose into short-chain fatty acids.
Why limit that concept to non-industrial societies?
What do you think happens in your colon?
> [@](#):
>
> **Short-chain fatty acid formation at fermentation of indigestible carbohydrates**
> By Asa Henningsson, Inger Bjorck and Margareta Nyman
> _Scandinavian Journal of Nutrition ~Vol 45:16.5-168, 2001_
> In Western societies, about 20-60 g of the daily carbohydrate intake escapes digestion and absorption in the small intestine and reaches the colon as a potential source for fermentation (1).
>
> A considerable microbial flora, which amounts to 10" bacteria per gram content, is present in this organ. The colonic microflora contains about 400 to 500 bacterial species, but most are in small numbers (2). Most of the microorganisms are saccharolytic.
>
> The fermentation products, with carbohydrates as fermentation substrate, are mainly short-chain fatty acids (SCFAs; acetic, propionic and butyric acid) and gases (CO, CH, and H,). These end products are either excreted in the stool or absorbed from the colon (Figure 1).
>
> In the 1960s, SCFAs were believed to be poorly absorbed, causing diarrhoea through osmotic fluid retention in the stool. However, it is now known that about 90% of these SCFAs are rapidly absorbed by the colon, stimulating water and
> sodium absorption (3). Fermentation of indigestible carbohydrate to SCFAs thus reduces the osmotic load and there is also increasing evidence that the individual SCFA may have specific roles, including beneficial health implications.
Of course, you aren’t going to thrive if you are relying on the absorbed SCFA from the fermentation of 20g of carbohydrate.
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### Author:  [@Surreal](https://boards.straightdope.com/u/Surreal)
#### Post date: [September 9, 2015, 1:58pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/29 "2015-09-09T13:58:14Z")
> [@penultima\_thule](#):
>
> Why limit that concept to non-industrial societies
Here’s why:
[http://www.pnas.org/content/107/33/14691.full.pdf](http://www.pnas.org/content/107/33/14691.full.pdf)
> [@](#):
>
> Gut microbial composition depends on different dietary habits just as health depends on microbial metabolism, but the association of microbiota with different diets in human populations has not yet been shown. In this work, **we compared the fecal microbiota of European children (EU) and that of children from a rural African village of Burkina Faso (BF), where the diet, high in fiber content, is similar to that of early human settlements at the time of the birth of agriculture**. By using high-throughput 16S rDNA sequencing and biochemical analyses, we found significant differences in gut microbiota between the two groups. **BF children showed a significant enrichment in Bacteroidetes and depletion in Firmicutes (P \< 0.001), with a unique abundance of bacteria from the genus Prevotella and Xylanibacter, known to contain a set of bacterial genes for cellulose and xylan hydrolysis, completely lacking in the EU children**. In addition, we found significantly more short-chain fatty acids (P \< 0.001) in BF than in EU children. Also, Enterobacteriaceae (Shigella and Escherichia) were significantly underrepresented in BF than in EU children (P \< 0.05). **We hypothesize that gut microbiota coevolved with the polysaccharide-rich diet of BF individuals, allowing them to maximize energy intake from fibers while also protecting them from inflammations and noninfectious colonic diseases. This study investigates and compares human intestinal microbiota from children characterized by a modern western diet and a rural diet, indicating the importance of preserving this treasure of microbial diversity from ancient rural communities worldwide.**
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### Author:  [@Doctor\_Jackson](https://boards.straightdope.com/u/Doctor_Jackson)
#### Post date: [September 9, 2015, 5:16pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/30 "2015-09-09T17:16:04Z")
> [@Colibri](#):
>
> New restaurants would spring up, offering Kentucky bluegrass, tall fescue, ryegrass, Bermuda grass, with sweetgrass for dessert.
Lemongrass for your tea, Sir?
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### Author:  [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)
#### Post date: [September 9, 2015, 5:59pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/31 "2015-09-09T17:59:17Z")
> [@Colibri](#):
>
> It isn’t just the bacteria you need, but an entire new anatomy. If you want to get sufficient nutrition from grass, you would have to eat enormous amounts of it and keep it in your stomach for a long time as it ferments.
This is supposedly why gorillas have such enormous guts.
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### Author:  [@Scribble](https://boards.straightdope.com/u/Scribble)
#### Post date: [September 10, 2015, 12:18pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/32 "2015-09-10T12:18:42Z")
Nm
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### Author:  [@Gothic](https://boards.straightdope.com/u/Gothic)
#### Post date: [September 10, 2015, 2:32pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/33 "2015-09-10T14:32:44Z")
I see a huge dustbowl in states that have legalized a certain drug because the roots taste the best.
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### Author:  [@Malthus](https://boards.straightdope.com/u/Malthus)
#### Post date: [September 10, 2015, 2:39pm UTC](https://boards.straightdope.com/t/if-humans-could-digest-cellulose/730298/34 "2015-09-10T14:39:46Z")
… Someone would market a chewing gum named “Cud”. 😉
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