This thoughts on comparative anatomy......
One of the main differences of humans compared to animals,
including apes is: the much bigger brain, especially in
percentage (Elephants have bigger brains and much bigger bodies).
This results in our brain consuming a much bigger percentage of
metabolic energy than any animals brain.
This fact has been used from some scientists as an indication that
our anchestors had to switch to a "denser" food as in the fruit and
leave nutrition found in earlier and other primates.
This denser foods - they are indicated by fossil records too -
are suspected to have been animal carcasses
(hunted or scavenged) but may also have been denser plants e.g.
plant's storage organs, roots, tubers , plant seeds and nuts.
Our brain needs at rest 315kcal per day,
normally about 480 kcal. (120 g glucose) - pretty much.
And it needs this energy the form of glucose - a carbohydrate.
Brain is the only tissue (besides blood) which
has a mandatory need of its energy
to be in the form of carbohydrates.
See (1) http://medtstgo.ucdavis.edu/endo/lecture/metGlucose.htm
If the food is devoid of carbohydrates then the body can generate
the necessary amount (180 g Glucose for brain and blood!)
from protein, with a process called gluconeogenesis.
The brain alone would need 200g of protein to be broken down for
fuel.
This is what is in about *2 lbs* of lean meat.
You can decide between 5 small bananas or 2 lbs of meat
(in portions distributed in more meals over the day because
protein storage of the body contains only about 55g at a time).
This gluconneogenesis is a process typical to predators (e.g. cats)
and necessary for us in times of starvation for glucose supply.
It is however, compared to direct carb ingestion a little costly:
1.It requires the excess nitrogen and nuclein acids (purins)
to be excreted -done by creating ammonia and urea
leaving the body through the kidneys
2.It uses up additional calcium and disturbs the acid-base balance
3.Ammonia is toxic, especially just for the brain -see (3).
There is some more energy needed for the rest
of the body, besides brain. Where does it come from?
The *rest* of the energy (for example 2400-480 = about 2000 kcal)
may come from fat or carbohydrate or more protein.
If there *is* a fat supply it may relieve the need for the additional
carbs or protein beyond the needs of the brain.
If we didn't have fat or carbohydrate, then the above numbers
would multiply 5-fold to 1000g protein (or 5 kg of meat per day)
If paleo-humans were lucky, then they were able to replace the
additional 4kg meat (2000 kcal) by about only 200g of fat.
This is why fat is so valuable and high-priced.
Unfortunately wild game contains only about 4% of fat (4).
While nuts contain about 63% (walnuts).
Particularly dense *especially in terms of metabolic energy* are
tree seeds: nuts. Very rich in fats, they relieve the body from
a gigantic intake of protein or carbohydrate.
Also dense in terms of energy are roots, they replace the fat content
by carbohydrate content (about 2 kg root per day for 2400 kcal).
Summary: density in terms of metabolic energy is *not* given with
animal carcasses (meat), except when only minor parts were used
(only the fatty brain and marrow or adipose).
Density *is* given in the form of fatty foods. Fatty foods in
paleo-africa are - nuts (about 300 g per day enough).
Tubers and roots (maniok e.g.) may also be a reasonable dense food.
Speaking of comparative anatomy therefore i find that
the increased metabolic energy needed by the bigger brain
and smaller gut may point to a denser food
but not to animal carcasses.
I see a hint towards an increased usage of nuts and roots.
Does this sound logical to you?
I'd be looking forward to some counterarguments.
Implications for a modern diet implementation:
At least 500kcal per day should come from carbohydrates,
because this is what we need *at least* in this form
for our brain and blood cells.
Carbohydrates should only come from sources which
have the vitamins needed for its
usage too, namely vitamin b1 (with at least 3mg per 1000g carb).
Nuts or seeds or whole plants, not sugars, not honey, not flour.
The rest of our energy may -maybe should- come in the form of fats.
Which fats to prefer is annother question (and easy decision).
These two sources should represent enough for
our dayly energy requirements (e.g. 2400 kcal)
because otherwise protein needs will increase astronomically.
regards
Amadeus Schmidt
references
(1) http://medtstgo.ucdavis.edu/endo/lecture/metGlucose.htm
(2) http://www.beyondveg.com/billings-t/comp-anat/comp-anat-4a.shtml
(3) http://medtstgo.ucdavis.edu/endo/lecture/metProtNit.htm
(locate "Ammonia Toxicity")
(4)
http://maelstrom.stjohns.edu/CGI/wa.exe?A2=ind9709&L=paleodiet&P=R141
1
<<The amount of animal fat is based on the average fat
content of 43 species of present-day wild game from three
continents. The average is 4.3%, with a range from around 1-8%.
This is far below choice beef sirloin at 27%.>>
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