Keep it up in the future!

J. Stanton said
Humans, as we collectively exist today, can survive off of a wide range of diets. That being said, I believe the optimal diet generally involves a higher percentage of calories from animal sources (including fish and shellfish) than from plant sources -- and that the plant-source calories should be from plants (e.g. vegetables and tubers) and not acellular carbohydrates (e.g. grains and sugars).

I contend this from several angles:
1. It's the most parsimonious interpretation of the archaeological evidence
2. The nutrient density of animal foods is far higher
3. Our digestive and metabolic systems are not great at interconverting nutrients, unlike those of an herbivore (which ferments cellulose to SCFAs) or a pure carnivore (which is much better at gluconeogenesis)
4. Humans are incompletely adapted to high-starch diets (see below)
5. 40 years of low-fat dietary recommendations, and the shift from animal to seed-sourced fats, has made America fatter than ever
JS

1. Archaeological evidence concerning what early humans ate? If so, it is widely debatable on what Paleolithic humans ate. It is known that Paleolithic humans existed in a wide variety of environments which points to a wide variety of diets.
2. Not necessarily. Yes, organ meats can be dense in nutrients but, plant foods have a high nutrient density (excluding most grains). Foods like kale, broccoli, blueberries (most berries in general), many nuts, and some seeds (almonds).
3. Interconverting nutrients? What exactly does that mean? Why does our ineptness at interconverting nutrients mean we are better suited for a animal-based diet?
4. Response below (where you address it specifically)
5. I agree, fatty foods do not necessarily cause weight gain. Though, I don't agree that seed-based fats are the main problem. I blame processed foods in particular.

J. Stanton said
-Regarding amylase section-
JS

I cannot access the full paper (from nature.com). If that article describes why exactly low copy numbers of the AMY1 gene put people at a greater risk for obesity, I could give you a proper answer. Maybe somewhere on the net I can find similar information that is available to the public for free.

In response to the GI tract related part of the post:
I must ask, where are you getting these measurements for horses I can't seem to find any. I wanted to see if there was much variation over different herbivore's intestinal length to torso length.

Humans still share many resemblances with gorillas, chimpanzees, and bonobos regarding the GI tract. (Also, some of that data may not be reliable according to the note below the chart.)

In response to the rest of the post:

The SAD is an example of a diet that one can survive on (not thrive). (The SAD also comes with many health risks including obesity, high blood pressure, etc.) People have had success with all kinds of diets (vegan, vegetarian, paleo). Like I stated before, it should be assumed Paleolithic humans ate a wide variety of different diets (since they lived in a variety of environments). It is still unknown as to what their diets were like exactly but you can see that Eskimos are living healthily on their diet and the Kitavans are able to thrive on their diet. Genetics play a large factor in what the optimal diet is for a specific person. This is why a paleo diet can work for some but not others. Same with vegetarianism.

I've been very busy this summer, primarily with my 2014 AHS presentation, and am just now catching up with all the unanswered comments -- including yours.

"Do you believe that humans are primarily carnivorous (about 75% animal based foods and 25% plant based) or omnivores that eat about equal amounts of animal and plant materials. (Please note, I'm not asking this based off of mass but off of caloric energy)."

Humans, as we collectively exist today, can survive off of a wide range of diets. That being said, I believe the optimal diet generally involves a higher percentage of calories from animal sources (including fish and shellfish) than from plant sources -- and that the plant-source calories should be from plants (e.g. vegetables and tubers) and not acellular carbohydrates (e.g. grains and sugars).

I contend this from several angles:
1. It's the most parsimonious interpretation of the archaeological evidence
2. The nutrient density of animal foods is far higher
3. Our digestive and metabolic systems are not great at interconverting nutrients, unlike those of an herbivore (which ferments cellulose to SCFAs) or a pure carnivore (which is much better at gluconeogenesis)
4. Humans are incompletely adapted to high-starch diets (see below)
5. 40 years of low-fat dietary recommendations, and the shift from animal to seed-sourced fats, has made America fatter than ever

"Doesn't our saliva contain amylase, an enzyme that breaks down amylose (a complex carbohydrate)?"

Yes, it does. So does the chimpanzee, which is primarily frugivorous and thus has little use for salivary amylase: thus it only has one copy of the AMY1 gene. Most interestingly, the amount of amylase humans produce varies dramatically between different people:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2377015/
"individuals from populations with high-starch diets have on average more AMY1 copies than those with traditionally low-starch diets."

J Nutr. 2012 May;142(5):853-8. doi: 10.3945/jn.111.156984. Epub 2012 Apr 4.
High endogenous salivary amylase activity is associated with improved glycemic homeostasis following starch ingestion in adults.
Mandel AL1, Breslin PA.
http://www.ncbi.nlm.nih.gov/pubmed/22492122
"HA individuals had significantly more AMY1 gene copies within their genomes than did the LA individuals. We found that following starch ingestion, HA individuals had significantly lower postprandial blood glucose concentrations at 45, 60, and 75 min, as well as significantly lower AUC and peak blood glucose concentrations than the LA individuals. [...] These observations are interpreted to suggest that HA individuals may be better adapted to ingest starches, whereas LA individuals may be at greater risk for insulin resistance and diabetes if chronically ingesting starch-rich diets."

Nat Genet. 2014 May;46(5):492-7. doi: 10.1038/ng.2939. Epub 2014 Mar 30.
Low copy number of the salivary amylase gene predisposes to obesity.
Falchi M et.al.
http://www.nature.com/ng/journal/v46/n5/abs/ng.2939.html
"The OR value of 1.19 per copy of AMY1 translates into about an eightfold difference in risk of obesity between subjects in the top (copy number > 9) and bottom (copy number < 4) 10% of the copy number distribution."

In other words, the process of human adaptation to a high-starch diet is incomplete, suggesting it 1. took place very recently and 2. is still in progress. Do you know how many AMY1 gene copies you have? Why take the risk?

Re: GI tract length, you're not comparing apples to apples. If you only count the human torso as "body length", you must also only count the equine torso as "body length". This means you can't count the head and neck, and the average horse is no longer 8-10 feet long! The average horse's back is 1/3 body length, so add a bit for the part of the croup behind the peak, and we'll call it slightly over half body length. (Stretch out a horse's neck and head...they're quite long!) Result: horse intestine = 18-22x torso length.

In contrast, the average human torso is about two feet long, for about 10x-14x torso length...so the human's still substantially shorter in comparison. (I didn't see that the upper-bound 30 foot figure I linked previously includes the esophagus and stomach, so the intestine is perhaps 28 feet. The lower-bound figure of 20 feet doesn't change.)

However, I find the comparison between us and our closest primate relatives is far more relevant. Humans have a smaller gut in proportion to body size, and much more of it is dedicated to the small intestine. For instance, a (folivorous) gorilla's colon comprises over half of its gut, as does a (mostly frugivorous, with occasional meat) chimpanzee's. In contrast, our own colon only occupies 17% of our gut, strongly suggesting a greatly reduced intake of plant foods.
(Ref: Milton 2003, p. 99. http://books.google.com/books?id=xHYxSHr86T8C&lpg=PA93&lr&pg=PA99#v=onepage&q&f=false)

Yes, humans can usually survive on what's available: people regularly grow to adulthood on a diet of McNuggets, takeout pizza, and gas station burritos! Furhtermore, the ability to survive periods of low prey availability would have no doubt been strongly selected for, which is why we're omnivores, not pure carnivores. However, I'm concerned with what's optimal for health, not just what allows us to survive...and the evidence points me towards a primarily animal-based diet. (By calories, though perhaps not by weight depending on the source.)

JS

J. Stanton said

Skgr:
Finally, our guts are NOT more like an herbivore's than a carnivore's: our stomach acid is just as strong as a carnivore's, and our digestive tract is NOT "much longer than a carnivore's." (Further discussion, including links to scientific literature, here.) Nor do we have a rumen or a cecum, necessary to extract significant energy from vegetation (the rumen and cecum are places where bacteria ferment vegetation into SCFAs.) And we don't need huge teeth, as we've been using sharp rocks for over 3 million years.

JS

Due to recent information I have found, I no longer agree with two of these points.

About the length of GI tract compared to body length: When we are talking about body LENGTH (shoulders to hips) we have to remember not to measure human height. If we compared our GI tract to height it would indeed be 3.2 to 5.2x the height of a human. If we compare our GI tract to body length it would be about the same ratio as an herbivore's. So our GI tract is much longer than a carnivore's, and it is about the same length (in proportion of course) as a herbivore's is to its body length.

Not all herbivores need a rumen and cecum. A rumen and cecum are needed for when plant material with loads of cellulose are eaten. (Leaves, stems, grasses.) Other herbivores only need a single chambered stomach. These herbivores eat (Fruit, nuts, seeds, some leaves (i.e vegetables that provide fiber in the form of cellulose) tubers, mushrooms, et cetera).

I believe that humans evolved to eat whatever is available. Some Paleolithic humans ate more meat (such as the Inuit) while others ate a significant amount of plant matter (can't remember the names of the people that ate like this but I believe they lived in South America, Africa, and Asia). That's why humans can find success in multiple diets from Paleo, to Vegetarianism, and more rarely, Veganism.

J. Stanton said

Skgr:

I don't content that a high-carb diet always causes metabolic inflexibility -- that's clearly not the case, and a combination of other factors Including genetic susceptibility) must also occur.

Also, I would be careful about generalizing your and your family's experience to the rest of the world: I've received many communications from people who find carbohydrate of any type addictive, regardless of taste.

Finally, our guts are NOT more like an herbivore's than a carnivore's: our stomach acid is just as strong as a carnivore's, and our digestive tract is NOT "much longer than a carnivore's." (Further discussion, including links to scientific literature, here.) Nor do we have a rumen or a cecum, necessary to extract significant energy from vegetation (the rumen and cecum are places where bacteria ferment vegetation into SCFAs.) And we don't need huge teeth, as we've been using sharp rocks for over 3 million years.

JS

First off, thank you for pointing out all those inaccuracies. I do have a few more to ask you about but first, a question. Do you believe that humans are primarily carnivorous (about 75% animal based foods and 25% plant based) or omnivores that eat about equal amounts of animal and plant materials. (Please note, I'm not asking this based off of mass but off of caloric energy).

Doesn't our saliva contain amylase, an enzyme that breaks down amylose (a complex carbohydrate)? It would make sense if humans were 50/50 omnivores but not if we were primarily carnivorous. Also, why do we have the ability to move our jaw left and right (presumably to grind up plant matter) if we are primarily carnivorous? Do you think that the paleo diet is suitable for all modern humans?

This is off topic though but why do (not all) vegetarians and vegans report success with their diet in the long term? I understand that vegans can "cheat" with supplements but what about lacto-ovo vegetarians that don't supplement any nutrients?

I don't content that a high-carb diet always causes metabolic inflexibility -- that's clearly not the case, and a combination of other factors Including genetic susceptibility) must also occur.

Also, I would be careful about generalizing your and your family's experience to the rest of the world: I've received many communications from people who find carbohydrate of any type addictive, regardless of taste.

Finally, our guts are NOT more like an herbivore's than a carnivore's: our stomach acid is just as strong as a carnivore's, and our digestive tract is NOT "much longer than a carnivore's." (Further discussion, including links to scientific literature, here.) Nor do we have a rumen or a cecum, necessary to extract significant energy from vegetation (the rumen and cecum are places where bacteria ferment vegetation into SCFAs.) And we don't need huge teeth, as we've been using sharp rocks for over 3 million years.

JS

Blood sugar spikes and crashes are only one contributor to hunger and weight gain: nutrition is a primary driver, as I've shown in my presentation "Why Are We Hungry?"  (Print articles here.)  So while slathering butter on a croissant does blunt the blood sugar spike (and adds at least a little bit of fat-soluble nutrition), substituting the white flour-based croissant with food that isn't just empty calories will keep you less hungry and produce better results.

To that end, sprouted bread will indeed be superior to other breads, but even the humble potato will provide superior nutrition -- and whole eggs, meat, and vegetables will be even better still. 

I agree that dark chocolate in moderation isn't a bad thing: the darker it is, the less sugar it contains vs. cocoa butter, antioxidants, and the odd stimulant and euphoric.  My current favorite is the Lindt 90%.

"But that has more to do with the cheaper processed foods in this country that is available to them. Not something they would eat living in Africa."

I agree.  Indigenous populations, whether Native American, Australian Aboriginal, or Pacific Islander, suffer much more from obesity, diabetes, and other "diseases of civilization" upon adopting a diet of processed industrial Western food than Westerners do -- whether they adopt the processed industrial diet in their homeland or upon moving to the West. 

JS

"Gluten-free bread" can contain any number of ingredients, as there's no universally accepted way to make it.  (Typical contents include potato starch, rice flour, tapioca starch, sorghum flour, bean flour, cornstarch, ...)

However, it's all just processed carbohydrate -- and while gluten is unhealthy for several other reasons, the usual effect of simply substituting gluten-free junk for the junk you used to eat is a diminution of your savings account.  (Gluten-free bread and cracker substitutes are expensive!)  It's best to substitute the bready junk you used to eat with real food -- meat, fish, eggs, vegetables (including root vegetables), some nuts and fruits.  Eat like a predator, not like prey.  

That being said, gluten-free junk is less bad for us than gluten-based junk, and I do indulge in an occasional treat...but it's still processed "carbohydrate" (sugar).

JS