AHS(?) Bumpity Bump Bump: When is Fat a Fat?

Soooo ... I've been following the #AHS12 hashtag on Twitter, and I'm not sure this came directly from there or from me clicking on an ID on one of the tweets and then checking out other tweets ... but anyway, I stumbled across this exchange between Aaron Blaisdell and Robb Wolf:

9 AugRobb Wolf ‏@robbwolf

Ruminant fermentation converts cellulose to fats. Cows actually run on a 60-70% FAT diet.

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16hAaron Blaisdell ‏@AaronBlaisdell

@robbwolf Paul Jaminet wrote the same thing in his book Perfect Health Diet

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7hEvelyn ‏@CarbSane

@AaronBlaisdell @robbwolf SCFA are not metabolized as "fats" . Ruminants convert the bulk of these via DNL to LCFA.http://carbsanity.blogspot.com/2011/02/when-is-fat-fat.html

FWIW, Robb retweeted this.  Now I'm pretty sure since he's at AHS12, this tweet came from a statement someone made in their presentation.  This is a claim I hear made from time to time -- that pretty much every animal being on the planet somehow consumes a high fat diet because when one eats the "right" carbs, gut bacteria convert them into short chain fatty acids.  This is a highly misleading concept as I attempted to outline in this post.   I hope that in revamping and adding to the book, the Jaminets will clarify the section on chain length to distinguish long, short and medium chain FA's (and leave out the part about SCFA qualifying as "fat burning" entirely ... it is generally the other way around in ruminants).

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Resistant Starch & Butyrate: Eades' Shmashthematics

While finally finishing off my last post on short chain "fatty" acids, I was reminded of a whopper of a post on Dr. Eades' blog that I came across a long ago on resistant starch and butyrate.  This post, too, has been in my Drafts for a very long time waiting for some finishing touches.

I came across this whilst I was looking into soluble fiber, low carbing and stalling and discovered that for all intent and purposes, SCFA's are carbohydrates metabolically, not fats at all.  On LC forums I was repeatedly told or reading that soluble fiber is not really a carb because it is converted to a fat therefore doesn't stimulate insulin (I've got a fair amount of info on this to summarize in a future post).  So this was one of the first things I began inquiring after.

I had read several highly informative pieces by Eades through links in discussions, etc.  But when I found and read this one, it perked my "fact check" bunny ears right on up.   He seemed to get so caught up in his smug condescension of the RD in the video (unfortunately no longer available)  that he was discussing, that he put out quite a bit of erroneous information of his own.   Don't get me wrong, the misinformation she was putting out deserved criticism and correction.  But Eades only compounded things with his analysis.

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Soluble Fiber and Net Carbs

I believe that, like sugar alcohols, soluble dietary fiber should be counted on a 0.5g carb/gram fiber basis.  However since most dietary fiber is not listed as to whether it is soluble or insoluble, this can be difficult to do.  Erring on the side of caution, a 1g for every 3g total dietary fiber would be a good compromise.  But many of the LC "fibers" such as polydextrose, inulin and glucomannan (shiritaki noodles) are essentially all soluble so 1g counted for 2g is a better count.

Insoluble dietary fiber, IDF, passes through the human digestive system unchanged so it is non-nutritive in all aspects. Further, since it adds bulk to food and assists in stool formation and "moving things along" IDF can reduce the nutrient absorbtion from the food we do eat.  This is essentially the rap of the "fiber is overrated" contingent.

SDF may not be metabolized by the body, but it is fermented in the large intestine to short chain fatty acids (SCFA) that are absorbed in the large intestine and metabolized. Some of these SCFA's are used by the intestines themselves as fuel, but the rest go mainly to the liver to be metabolized.

The "joys" of SDF are many from a weight loss and general health POV. To list a few I've read we have:

• When SDF absorbs water it swells forming a gel. This gives a feeling of fullness in the stomach and slows the progression through the digestive tract so you may feel full longer.
• This slowing of the digestion has been shown to improve the stability of BG levels in diabetics.
• SDF's are fermented in the large intestine to produce short chain fatty acids (SCFA's) that can be used by the intestine's cells as well as absorbed by the body. These SCFA's are believed to help with irritable bowel syndrome (IBS) by boosting the mucosal cells and perhaps reduce colorectal cancer risks. They are also believed to contribute to lowering LDL levels.
• SDF's do have a smaller than normal caloric nutritive value to us humans as compared to other carbs (1.5 cal/g to 2.5 cal/g, so I'll use an average of 2 cal/g)

What becomes of the rest of the SCFA's? We hear "fatty acid" and presume these are metabolized like other dietary fats, so eating soluble fiber has all the bennies above plus they are like ingesting fats!  But these are metabolized more like carbs -- the SCFA's are prime substrates for gluconeogenesis!!

According to this http://books.google.com/books?id=y2rvBwM...#PPA141,M1 (which focuses on inulin type SDF's) the major byproducts of SDF fermentation are lactate (15%) and SCFA's (40% of which these are further classified as approx 15% butyrate, 28% propionate and 67% acetate respectively). The SCFA's are absorbed or otherwise utilized for energy at a rather high 90-95% rate, and the latter two are either entirely (propionate) or partially (acetate) metabolized by the liver to PRODUCE GLUCOSE via gluconeogenesis (and lactate is also listed as a substrate for gluconeogenesis). Scroll down at this citation. 

I have read several reports around the LC webosphere of BG increases with low carb breads and pastas. And, of course, the numerous reported stalls many seem to experience when including these products in their diet. This may well be why. Those "fibers" are like eating half their grams in sugar.

Also consider that, like all bacteria, the population will increase when their food supply increases. So more SDF is feeding these. Sounds great for digestion, but these same bacteria also ferment something else -- "regular" carbs that have not been completely digested previously. So in addition to adding to your carbs, you are very likely increasing the digestion/absorbtion of the other carbs in your diet.  Be consoled that you have a healthy and efficient digestive system, but you may be getting more carbs than you accounted for.

There may well be some mitigating factors to this in terms of the inefficiency and/or energy requirements for the gluconeogenesis pathways for these substrates, but to me it seems pretty clear now that soluble fibers should NOT be subtracted on a 1:1 ratio to find net carbs. At best they could be subtracted as 1:2. Here's a link to one source of fiber content for a pretty good sized list of foods: http://huhs.harvard.edu/assets/File/OurS..._Fiber.pdf

Fatty Acid Contents of Foods: Butter & Coconut Oil

On occasion I look up this type of info on www.nutritiondata.com -- it comes from the pull-down analysis of the fats.  This is for one ounce (28g) of butter.  (NOTE:  I suspect there is an error here on the serving size vs. fat content.  Normally 1T butter has ~11g total fat)

Of note, a little more than 3% (~1/2 g) of the total fat is butyric acid, the short chain fatty acid product that is the byproduct of some soluble fiber metabolism.  Butter also contains 3.6% of capric and caprylic acids combined -- these are the 8 & 10 carbon medium chain triglycerides in "MCT oil".  Lauric acid (12C)  is 2.7% (this is the longest chain length characterized as medium chain, that is almost 50% of the fatty acid content of coconut oil).  All in all, the short and medium chain triglyceride content of butter is 11.6%, of which ~8.4% are classified as MCT's.  By contrast, coconut oil (source: wikipedia) is a little more than 60% MCT's.

The PUFA's are all Omega 6