Brian MacLean posted, and Loren Cordain responded:

4.      "With regard to pathology, a high intake of red meat has been
associated quite consistently with the development of cancers (6)."

        There is no doubt that multiple epidemiological studies have shown
an association between high consumption of red meat intake and many types of
cancers.  However, there is just as strong epidemiological evidence to show
a relationship between saturated fat intake and cancers (checkout medline,
there are thousands of references).  Because,  modern commercially available
red meat contain enormous amounts of saturated fat (a t-bone steak with 10%
fat by weight contains 50% fat by energy), it is quite difficult if not
impossible for epidemiological studies to untangle the effects of the meat
protein with the meat fat.  There is very little experimental evidence to
show that protein is a mutagen whereas there numerous animal studies and in
vitro cell studies indicate that high fat diets can serve as promoters of
many diverse cancers.  The  fat content of muscle meat in wild game animals
ranges from 1-2% by weight or about 10-20% by energy.  Thus, the muscle of game
meat (the staple food of hunter-gatherers) is almost entirely protein.


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In addition to the role that the saturated fat in modern meat
may be playing in contributing to cancer, I would like to
mention 2 other possible factors (which were not present in
the Paleo diet):

1) Pesticide residues from animal feed that concentrate in the fat
(perhaps this could partly explain the correlation between saturated
fat intake and cancer?)

2) Modern meat consumption generally takes place place in the
context of a low-fiber diet and relative inactivity, whereas
the Paleo diet was probably high in fiber (at least in plant-rich
regions) and high in activity. Both of these would contribute to
quicker passage of any negative (possibly carcinogenic) residues from
animal protein digestion through the digestive system.


Steve Meyers
Lawrence Berkeley Natl Lab