On 9 Jul 2005 17:30:32 GMT, John Sankey wrote in
<news:[email hidden]> on sci.med.nutrition :
Quoted message said:"From The Center for Genetics, Nutrition and Health, Washington, DC.
Human beings evolved consuming a diet that contained about equal
amounts of n-3 and n-6 essential fatty acids. Over the past
100-150 y there has been an enormous increase in the consumption
of n-6 fatty acids due to the increased intake of vegetable oils
from corn, sunflower seeds, safflower seeds, cottonseed, and
soybeans. Today, in Western diets, the ratio of n-6 to n-3 fatty
acids ranges from {approx}20-30:1 instead of the traditional
range of 1-2:1."
I have two major concerns with these statements.
First, the time scale. I'm old enough to well remember when lard,
suet and butter were replaced in Canada by margarines and
vegetable oils, and it was no 100-150 years ago, it was less than
60. For years after the introduction of margarine, the dairy
lobby made sure that it was illegal to sell any margarine here
unless it was yucky-looking white. (Later, it became legal to
include a dye packet. Margarines instantly became soft and were
packed in plastic bags so that all you had to do to have butter-
coloured margarine was to knead the unopened package.) I don't
remember when pre-coloured margarine became legal because I
couldn't stand the smell of early margarines, so always used
butter until I moved to Ottawa, where the large Italian
population ensured that fine olive oils were available.
Second, the reference population for 'traditional'. My mother's
family lived since 1818 over 100 miles from any significant fish-
bearing water. And, with transportation by farm horse and wagon
and with no refrigeration other than river ice, their consumption
of seafood was mighty close to zero. (No, they didn't use salted
fish - my mother never heard of it and my grandmother's recipe
box contains not a single mention of it.) They didn't grow flax,
they couldn't grow olives with the climate, so almost all their
lipids came from corn (maize), wheat, or grass-eating meat.
Before that, her family (including most of her in-laws) came from
the Alston Moor in England (see http://sankey.ws/wallacea.html),
where the diet would have been very similar for longer than we
have recorded history there, except that the primary grain would
have been barley. I don't believe they could have had anything
remotely close to an n6:n3 ratio of 2:1.
Personally, I aim for a maximum ratio of 4:1 and achieve it
easily, given the plentitude of fine fish resulting from air
transport and freezing (cf. http://sankey.ws/dietref.html). But,
I'm very uncomfortable with the claims made for 2:1, let alone
1:1, for my effective ancestry.
Actually it's not clear what they mean with "traditionally".
Here's another interesting bit about the n6:n3 ratio in history.
http://www.st-hs.com/TMA_Forum/PUFA%20-%20Calvani%20Benatti%20-%20Feb%202K3.pdf
Polyunsaturated Fatty Acids (PUFA)
CALVANI M. AND BENATTI P.
sigma-tau S.p.A. - Scientific Department
28.02.03
[...]
4. EVOLUTIONARY ASPECTS OF DIET
Studies of hunter-gatherer societies indicates that man evolved on a diet
that was low in
saturated fat and the amounts of n-3 and n-6 fatty acids was quite equal.
Over the past 10000 years with the development of agriculture, changes
began to take
place in the food supply, especially during the last 100-150 years, that
lead to increases in
saturated fat from grain-fed cattle; increases in trans-fatty acids from
the hydrogenation of
vegetable oils; and enormous increase in n-6 fatty acids (about 30 g/day)
due to the production of
oils from vegetable seeds such as corn, safflower, and cotton (Fig. 4) (4).
FIGURE 4. SCHEME OF THE RELATIVE PERCENTAGES OF DIFFERENT DIETARY FATTY
ACIDS AND POSSIBLE
CHANGES SUBSEQUENT TO INDUSTRIAL FOOD PROCESSING, INVOLVING ANIMAL
HUSBANDRY AND
HYDROGENATION OF FATTY ACIDS.
Increases in meat consumption have lead to increased amounts of arachidonic
acid (C20:4
n-6, AA), about 0.2-1.0 mg/day (5), whereas the amount of LNA is only 2.92
g/day (6) and
amounts of EPA, DHA are 48 and 72 mg/day, respectively. Thus a relative and
absolute decrease
in the amount of n-3 fatty acids has lead to an imbalance and increase in
the ratio of n-6/n-3.
Intake of n-3 fatty acids is much lower today because of the decrease of
fish consumption
and the industrial production of animal feeds rich in grains containing n-6
fatty acids, leading to
production of meat reach in n-6 and poor in n-3 fatty acids. The same is
true for cultured fish and
eggs (7; 8). Even cultivated vegetables contain fewer n-3 fatty acids than
do plants in the wild
(9). In today¢s diet this ratio is 20-30/1, whereas at the time when the
human genetic code was
established in response to diet, it was 1-4/1.
The ratio of n-6/n-3 in various populations, is reported in the following
table (Tab. 1).
TABLE 1. RATIOS OF N-6 TO N-3 FATTY ACIDS IN VARIOUS POULATIONS
POPULATION n-6/n-3 Ref.
Paleolithic 0.79
Greece before 1960 1.00-2.00
Current Greece 1.10-2.10
Current United States 16.74
Current United Kingdom and Northern Europe 15.00
Current Japan 4.00
BIBLIOGRAPHY
[...]
4. Leaf A, Waber PC. A new era for science in nutrition. Am J Clin Nutr
1987; 45:1048-53.
5. Phinney SD, Odin RS, Johnson SB et al. Reduced arachidonate in serum
phospholipids and cholesteryl esters
associated with vegetarian diet in humans. Am J Clin Nutr 1990; 51:385-92.
6. Raper NR, Cronin FJ, Exler J. Omega-3 fatty acid content of the US food
supply. Am J Coll Nutr 1992; 11:304-8.
7. Van Vliet T, Katan MB. Lower ratio of n-3 to n-6 fatty acids in cultured
than in wild fish. Am J Clin Nutr 1990;
51:1-2.
8. Simopoulos AP, Salem N Jr. n-3 fatty acids in eggs from range-fed Greek
Chickens. N Engl J Med 1989;
321:1412.
9. Simopoulos AP, Salem N Jr. Purslane: a terrestrial source of omega-3
fatty acids. N Engl J Med 1986; 315:833.
10. Eaton SB, Eaton SB III, Sinclair Aj et al. Dietary intake of long-chain
polyunsaturated fatty acids during the
paleolithic World Rev Nutr 1998; 83:12-23.
11. Simopoulos AP. Overview of evolutionary aspects of omega-3 fatty acids
in the diet. World Rev Nutr 1998;
83:1-11.
12. Simopoulos AP. The Mediterranean diet: what is so special about the
diet of Greece? The scientific evidence. J
Nutr 2001; 131:3065S-73S.
13. Sanders TAB. Polyunsaturated fatty acids in food chain in Europe. Am J
Clin Nutr 2000; 71(suppl):S176-S8.
14. Sugano AM, Hirata F. Polyunsaturated fatty acids in food chain in
Japan. Am J Clin Nutr 2000;
71(suppl):S189-S96.
[...]
