I'd like to thank Loren Cordain for clearing up this issue of the fat and
protein content of Kangaroo. I for one have been confused about the issue
of whether it was weight or percentage of energy returned that was most
important.
Sean McBride
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> Subject: PALEODIET Digest - 22 Jul 2000 to 6 Aug 2000 (#2000-20)
> Date: Monday, August 07, 2000 6:00 AM
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> Topics of the day:
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> 1. Kangaroo fat and protein poisoning
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> Date: Sun, 6 Aug 2000 13:24:45 -0600
> From: Loren Cordain <[log in to unmask]>
> Subject: Re: Kangaroo fat and protein poisoning
>
> I'd like to respond to Sean McBride's post of July 14th regarding
kangaroo
> fat and the physiological protein ceiling. Gould's (1) observation that
a
> 97 lb (44 kg) kangaroo yielded only 4 ounces (114 g) of removable fat
would
> not give the true picture of the total carcass fat because it doesnt
account
> for endogenous, non-dissectable structural and storage fat. Additionally,
> fat given by weight rather than by energy for wild animal carcasses is
> misleading because it doesn't adequately reveal the carcass protein/fat
> relationships.
> It is possible to mathematically re-arrange the Pitts and
Bullard
> regression (2) and solve for % body fat from body weight rather than FFM
> such that (log % body fat = 0.357 + 0.177 x (log body wt (g); r =0.75;
SEE =
> 0.27). So, a 44 kg kangaroo would be predicted to have 8.2% body fat by
> weight (360.8 g) if one were to homogenize the entire carcass and
chemically
> extract the total lipid mass. If one subtracts the amount of fat that
Gould
> was able to dissect (114 g) from the predicted total carcass fat (360.8
g),
> the remaining figure (246.8 g) represents the predicted non-dissectable
> lipid. The endogenous non-dissectable lipid in the tissues of wild
animals
> averages 2.1 % by weight for muscle, 3.8 % for liver, 9.3% for brain, 51%
> for marrow and 82.3 % for subcutaneous storage fat (3). Hence, the
residual
> fat (~ 250 g) that Gould was not able to extract lies primarily as
> structural lipid in muscle and other organs. Additionally storage
> triglyceride would be present in marrow (it is unclear if Gould used
marrow
> in his estimates).
> Using the 3rd order polynomials that we have developed (4), it is
> possible to now examine the true energetic relationships between fat and
> protein in our 44 kg kangaroo in light of the physiologic protein
ceiling.
> The total carcass food by energy would be 46% fat and 54% protein. Since
> the maximal protein ceiling in humans averages about 35% of total energy
> (4), then most of the kangaroo edible carcass could be consumed,
providing
> the fat were divided evenly and that just a small amount of carbohydrate
> from plant food were available. Fat can even be extracted from
non-edible
> portions (cancellous bone tissues) of the carcass by boiling them. Also,
> remember that the protein ceiling is an absolute number (i.e. grams of
> protein, not % total calories) - consequently, high amounts of protein
> could be eaten for a number of consequtive days, as long as either a fat
or
> carbohydrate source were eventually found to make up the caloric
deficiency
> that was dictated by the excessive lean meat. Only when lean meat is the
> sole available food source day after day will symptoms of protein
toxicity
> emerge.
> Human's living at northern latitudes preferentially hunted
megafauna
> because these beasts contained both absolutely and relatively more fat.
> Hence, at northern latitudes wherein carbohydrate (plant food) sources
are
> seasonally restricted, the fat obtained from larger mammals was
sufficient
> to dilute the lean protein from muscle tissues. The fossil record shows
> that the worldwide extinction of animals that took place at the end of
the
> Pleistocene occurred primarily in animals over 100 kg (220 lbs) (5).
Using
> the Pitts and Bullard regression (2), a 220 lb mammal would be expected
to
> have about 15% body fat. Applying our cubic regressions (4) to this
value,
> a 220 lb mammal would have 60 % of its total body energy as fat and 40%
as
> protein. The protein value then is very close to maximal protein ceiling
> (also 40 % of energy) -- hence it is not surprising that the "cutoff"
> values for megafauna extinction (100 kg) corresponds almost exactly to
the
> value for the maximal physiological protein ceiling in humans. In
animals
> weighing less than 100 kg, the entire carcass cannot be consumed unless
> there is a carbohydrate source, whereas in animals weighing more than 100
> kg, the entire carcass can be eaten with no worry about protein toxicity
and
> with no need to find a carbohydrate source.
>
>
>
>
> REFERENCES
> 1. Gould RA. Notes on hunting, butchering and sharing among the
> Ngatatjara and their neighbours in the Western Australian desert. Kroeber
> Anthropological Society Papers 1966;36:41-63.
> 2. Pitts GC, Bullard TR. Some interspecific aspect of body
composition
> in mammals. In: Body composition in animals and man. Washington D.C.:
> National Academy of Sciences, 1968:45-70. (Publication 1598).
> 3. Cordain L, Watkins BA, Mann NJ. Fatty acid composition and energy
> density of foods available to African hominids: evolutionary implications
> for human brain development. World Rev Nutr Diet, in press.
> 4. Cordain L, Brand Miller J, Eaton SB, Mann N, Holt SHA, Speth JD.
> Plant-animal subsistence ratios and macronutrient energy estimations in
> worldwide hunter-gatherer diets. Am J Clin Nutr 2000;71:682-92.
>
> 5. Stuart AJ. Mammalian extinctions in the late pleistocene of
> northern eurasia and north america. Biol Rev 1991;66:453-562.
>
>
> Loren Cordain, Ph.D., Professor
> Department of Health and Exercise Science
> Colorado State University
> Fort Collins, CO 80523
> tel: (970) 491-7436
> fax: (970) 491-0445
> email:[log in to unmask]
> http://www.colostate.edu/Colleges/CAHS/ess/cordain.htm
>
> ------------------------------
>
> End of PALEODIET Digest - 22 Jul 2000 to 6 Aug 2000 (#2000-20)
> **************************************************************
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