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Pound for pound could mixed leafy greens be as energy dense as cooked lean meat?

by (10994)
Updated about 2 hours ago
Created March 14, 2014 at 7:10 PM

http://jn.nutrition.org/content/127/10/2000.full

Seems that fibers in leafy vegetables convert largely into O3 fatty acids in hominid models at a rate of approximately 170 calories per 100 grams. Does anyone have any evidence that humans can or cannot ferment these same amounts of fibers to equivelant amount of SCFAs?

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10994 · March 15, 2014 at 2:33 PM

I agree, those are fair points.

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10994 · March 15, 2014 at 11:55 AM

Okay, I'll give you +1 because of this comment, thank you for clarifying.

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1147 · March 15, 2014 at 3:20 AM

with 9 meters we get 30% efficiency, give or take a few. So I think, with the evidence we have today, we can create amounts of butyrates, acetic acid, propionic acid, in amounts that can largely prevent inflammation, and give us a 200 calories/day boost. but not enough to live on. Also, these are not O3, they are SCFA.

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10994 · March 15, 2014 at 2:56 AM

The 1.5-1.7 kcal per gram of dry matter reported was from otherwise indigestible fiber exclusively. In the report you can see that they've already accounted for the amounts of proteins, fats and digestible carbs before accounting for the conversion of the otherwise dry fibrous matter. The study is linked in my above post. That being said, you are right that the fermentation bugs don't work for free, it mentions and cites their costs in the article.

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10176 · March 15, 2014 at 2:27 AM

100 dry grams of dry spinach contains about 400 total calories, both digestible and indigestible. If you ferment this by the method in the report and get 170 calories of O3 fatty acids, the conversion efficiency is 40-45%, lower than the 60% efficiency you'd get just by digesting it. Apparently the fermentation bugs don't work for free. On the other hand, you get fatty acids instead of glucose.

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10994 · March 14, 2014 at 11:58 PM

Hmm, that's a good point, it looks like my study is being done on a dry solids basis as you mentioned. Which would mean, that even "Studies in humans have indicated that dietary fiber is... 80% fermentation of leafy vegetables (e.g., cabbage) (Cummings 1982). Approximately 75% of the energy resulting from fermentation can be used by the host in the form of absorbed SCFA: acetate, propionate and butyrate (Cummings 1981, McNeil 1984)." would apply on a dry weight basis. Which would mean that pound per pound of fresh produce leafy greens would be closer to 1/6th=1/10th as calorically dense.

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10994 · March 14, 2014 at 11:25 PM

Okay, so you're saying that with a 30 meter gut we get a baseline efficiency of 100% but with 7 meters (which should actually be 9 meters) we get 0% efficiency?..

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10176 · March 14, 2014 at 11:34 PM

I took raw spinach as a model leafy green. USDA lists 100g spinach as containing 23 calories using a normal human digestive system. Spinach is 91% water and even if the 9g dry solids was pure fat (which it's not - it's a mixture of digestible and indigestible carbs - 23 calories is consistent with 60% digestible carbs) you'd only have about 80 calories max. Maybe the report you're reading is on a dry solids basis.

http://ndb.nal.usda.gov/ndb/foods/show/3214?fg=&man=&lfacet=&format=&count=&max=25&offset=&sort=&qlookup=Spinach

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10994 · March 14, 2014 at 11:58 PM

Hmm, that's a good point, it looks like my study is being done on a dry solids basis as you mentioned. Which would mean, that even "Studies in humans have indicated that dietary fiber is... 80% fermentation of leafy vegetables (e.g., cabbage) (Cummings 1982). Approximately 75% of the energy resulting from fermentation can be used by the host in the form of absorbed SCFA: acetate, propionate and butyrate (Cummings 1981, McNeil 1984)." would apply on a dry weight basis. Which would mean that pound per pound of fresh produce leafy greens would be closer to 1/6th=1/10th as calorically dense.

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1147 · March 15, 2014 at 2:29 PM

I am all for fermentable fiber, but why not do this study with, say, carrots, or apples? Also, I note that all animals (gorilla, deer, rabbit, goats) will graze tender growth first. I am mentioning this because IMO the amount of fermentable fiber varies widely in leaves. Unlike the other edibles I mentioned.

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10994 · March 15, 2014 at 2:33 PM

I agree, those are fair points.

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1147 · March 14, 2014 at 9:19 PM

All you need is a 30 meters long gut and you are all set. With only 7 meters, no.

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10994 · March 14, 2014 at 11:25 PM

Okay, so you're saying that with a 30 meter gut we get a baseline efficiency of 100% but with 7 meters (which should actually be 9 meters) we get 0% efficiency?..

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