This message is mainly for Amadeus, who argues that we should be
eating relatively little protein.

I have done a good deal of research lately on the matter of
protein use.  The best conclusion that I can reach is that the
human body is capable of adapting to a wide range of protein
intake levels without adverse consequence.  There really is some
evidence that people who have higher activity levels do better
with more protein, too.  The rate of protein "turnover" in the
cells changes to match the rate of protein intake.

One of the points that Amadeus makes seems to be correct:  If you
eat more protein, and you don't want that protein to be used as
energy fuel, then you must eat more calories.  This implies a
ceiling to the percentage of calories that can come from protein
without forcing the body to burn the protein as fuel, but I don't
know what that percentage is.

I want to emphasize, however, another role of dietary protein
that Amadeus doesn't mention.  Protein, unlike carbs and fats,
stimulates the pancreas to produce the hormone glucagon, the
antagonist of insulin.  Just as insulin facilitates the storage
of body fat, glucagon makes it easier to burn body fat as fuel.
Furthermore, whatever one thinks of the particulars of the Zone
diet, Barry Sears must be credited with making accessible the
effect of protein (and carbs) on the eicosanoids, the short-lived
signal hormones that govern so many physiological processes, with
vast health implications.  The effect of protein on the
eicosanoids is mediated by glucagon.  For example, glucagon
accelerates the conversion of dietary linoleic acid (LA) into
gamma linoleic acid (GLA), by up-regulating the activity of the
delta 6 desaturase enzyme.  It also favors the conversion of GLA
into the generally "good" series 1 eicosanoids.  This may explain
why Wolfe found that higher protein intake reduces risk of
atherosclerosis (BM Wolfe, Potential role of raising dietary
protein intake for reducing risk of atherosclerosis.  Can J.
Cardiol. 1995; 11 (supp G): 127G-131G. and BM Wolfe, Short term
effects of substituting protein for carbohydrate in the diets of
moderately hypercholesterolemic human subjects. Metabolism
1991;40:338-43).

Oddly enough, the last time I checked Sears' bibliography did not
mention Wolfe.  Anyway, Sears' research suggests that .5 to 1.0
grams of protein per pound of body weight, depending on activity
levels, is about right, and the ratio of carbs to protein should
not be higher than 9/7.  This comes to 30% protein *on a
hypocaloric diet*.  If you increase calories for "maintenance",
as many Zoners do, you must add fat, and the percentage of
calories from protein is diminished (although it remains constant
in absolute terms).  This means that in practice Zoners eat
between 20% and 30% of their calories as protein.  This fits very
nicely with Wolfe's results, and with estimates of typical
hunter-gatherer diets.  Pemmican is about 20% protein, for
example.

I conclude that the case for protein intake of 20-30% of calories
is fairly strong.  In addition, I believe that this can be
accomplished in a nutritious way by using mostly animal protein,
mostly plant protein, or a combination of both.

Todd Moody
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Todd Moody
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