In light of recent postings concerning the benefits of nut
consumption, in conjunction with the fact that nuts would have
been part of the human diet during most or all of our
evolutionary history, I want to share a conjecture or two.
Since I am not a scientist or any sort of expert in nutrition, I
hope those who are more qualified will comment.

Anyway, in the course of browsing through Medline I noted that
the protein casein can be used in laboratory studies to induce
elevated cholesterol in animals [1].  The explanation for this
is, apparently, the fact that the casein protein has a low
arginine:lysine ratio.  Another study [2] also suggests that the
arg:lys ratio has a significant effect on cholesterol.

Most of the literature on the health benefits of nuts deals with
their monounsaturated fat content, which is high.  I had the idea
of checking their arg:lys ratio in the USDA database and
discovered that many nuts have quite high ratios, among the
highest of any foods that I looked at.  Here are some samples:

Food            arg:lys ratio
-----------------------------
walnuts                 5.1
filberts                5.5
brazil nuts             4.8
almonds                 4.2
lentils                 1.1
milk                     .4
beef                     .7
sardines                 .7
whole wheat flour       1.5
chicken breast           .8
turkey                   .8
peanuts                 3.4
black beans              .9
sunflower seeds         2.7

Well, that gives some idea.  The arg:lys ratio of the nut
proteins is significantly higher than that of most other foods,
with the interesting exception of peanuts.  Loren Cordain
recently posted some information on the atherogenic properties of
peanut oil.  Yet another (partisan) study suggests that whole
peanuts are associated with reduced CHD risk [3].  The suggested
explanation is that the peanut contains resveratrol, but perhaps
the arg:lys ratio is another factor.

Todd Moody
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1. Kurowska EM, Carroll KK.  Effect of high levels of selected
dietary essential amino acids on hypercholesterolemia and
down-regulation of hepatic LDL receptors in rabbits.  Biochim
Biophys Acta 1992 Jun 22;1126(2):185-191

2. Rajamohan T, Kurup PA. Lysine: arginine ratio of a protein
influences cholesterol metabolism. Part 1--Studies on sesame
protein having low lysine: arginine ratio.  Indian J Exp Biol
1997 Nov;35(11):1218-1223

3. http://www.peanut-institute.org/Resveratrol_Abstract.html

Todd Moody
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