Ben,

this is nice complementary information. The Rait article underscores the
relevance of a reduced retinal blood flow. The current theory says that
in the small retinal vessels the (possibly omega-6 triggered) adherence
of a single leukocyte (nice photos in 1) may trigger the complete sequence
of events leading to stop of flow and endothelial apoptosis.

Prof. Beaumont probably refers to a case-control study (2) and
a prospective study (3) showing that

(2)"...Higher vegetable fat consumption was associated with an elevated
risk for AMD(age-related macular degeneration). After adjusting for age,
sex, education, cigarette smoking, and other risk factors, the odds
ratio (OR) was 2.22 .... for persons in the highest vs those in the
lowest quintiles of intake (P for trend,.007). The risk for AMD was
also significantly elevated for the ... intake of monounsaturated
(OR, 1.71) and polyunsaturated (OR, 1.86) fats (Ps for trend,.03 and
.03, respectively). Higher consumption of linoleic acid was also
associated with a higher risk for AMD (P for trend,.02). Higher intake
of omega-3 fatty acids was associated with a lower risk for AMD among
individuals consuming diets -->low in linoleic acid<--, an omega-6
fatty acid (P for trend,.05; P for continuous variable,.03). Similarly,
higher frequency of fish intake tended to reduce risk for AMD
when the diet was low in linoleic acid (P for trend,.05).
Conversely, neither omega-3 fatty acids nor fish intake were related
to risk for AMD among people with -->high levels of linoleic acid
intake.<--"

and

(3)"...Higher total fat intake increased the risk of progression to the
advanced forms of AMD, with a relative risk (RR) of 2.90 ..., after
controlling for other factors (P trend =.01). Animal fat intake was
associated with a 2-fold increased risk of progression (RR, 2.29 ...),
although the trend for increasing risk with higher animal fat intake
was -->not significant (P=.09).<--
Higher vegetable fat intake had a stronger relationship with increased
risk of AMD progression with an RR of 3.82 ... (P trend =.003).
Saturated, monounsaturated, polyunsaturated, and transunsaturated fats
increased the likelihood of progression (RR, 2.09 and P trend =.08;
RR, 2.21 and P trend =.04; RR, 2.28 and P trend =.04;
RR, 2.39 and P trend =.008, respectively). Higher fish intake was
associated with a lower risk of AMD progression among subjects with lower
linoleic acid intake. Processed baked goods, which are higher in some of
these fats, increased the rate of AMD progression approximately 2-fold,
and nuts were protective.

It is of note that in the paper (3) patients were excluded who ever had
a diagnosis of cancer. As cancer is related to the omega-6 intake, too,
this might have even weakened the significances.

Furthermore, all animal fat related variables (saturated fats, high fat
dairy, meat) lost their significances after controlling for vegetable
fats and other variables while the significances of vegetable fats
rose after controlling for animal fat.

And we should not forget the omega-6 content of grain fed pork and
poultry, accounting for a major part of western animal fat intake and
thus possibly leading to p-values close to significance (e.g. that 0.09
and 0.08 for animal and saturated fat, respectively).

The authors state that nut intake is possibly protective because of
other constituents and significance became borderline after controlling
for other variables.

These studies together with the Chen (and Lindeberg) study (ref. in my
february-posting) show again that the omega-6 FAs have to be considered
as one of the major neolithic nutrients as far as pathogenetic
processes are concerned. Many diseases of civilization have a long
history. Even the ancient egypts knew many of them. But a diet
consisting basically of whole-grain products (like in egypt) is not so
different from what grain-fed animals consume. Comparable adipose
tissue contents of omega-6 acids can be assumed *especially* if the
absolute fat consumption is low and consists mainly of germ oils or
other fats with a high omega-6 fraction.

roland


(1)
Joussen AM, Murata T, Tsujikawa A, Kirchhof B, Bursell SE, Adamis AP.
Leukocyte-mediated endothelial cell injury and death in the diabetic
retina. Am J Pathol. 2001 Jan;158(1):147-52.

(2)
Seddon JM, Rosner B, Sperduto RD, Yannuzzi L, Haller JA, Blair NP,
Willett W.
Dietary fat and risk for advanced age-related macular degeneration.
Arch Ophthalmol. 2001 Aug;119(8):1191-9.

(3)
Seddon JM, Cote J, Rosner B.
Progression of age-related macular degeneration: association with
dietary fat, transunsaturated fat, nuts, and fish intake.
Arch Ophthalmol. 2003 Dec;121(12):1728-37.