now.  At least these researchers are honest enough to admit what their
experiment revealed, unlike so many others who begin with assumptions
about how very dangerous fatty acids are "essential" to humans when one

rat experiment was done in 1929/30 (Burr & Burr), before all essential
nutrients, such as some of the B vitamins, were known, and thus any
experiment done at that time would have to be done again with all the
known nutrients, controlling for what is being tested for essentiality
(plus, dogs would be better than rats for this experiment - much closer

to humans in terms of fatty acid metabolization). <<

COMMENT:

A lot of experimental evidence has demonstrated the need of n-3 and n-6
EFAs in the diet of both young and old mammals since 1930. You seem to
be having difficulty either finding it or retaining it.  Perhaps a
shortage of n-3 in your own brain?

SBH

Br J Nutr. 2000 Dec;84(6):803-12.

The conditional nature of the dietary need for polyunsaturates: a
proposal to
reclassify 'essential fatty acids' as 'conditionally-indispensable' or
'conditionally-dispensable' fatty acids.

Cunnane SC.

Department of Nutritional Sciences, Faculty of Medicine, University of
Toronto,
Canada. cunnane@utoronto.ca.

The term essential fatty acid no longer clearly identifies the fatty
acids it
was originally used to describe. It would be more informative if the
concept of
essentiality shifted away from the symptoms arising from the lack of de
novo
synthesis of linoleate or alpha-linolenate and towards the adequacy of
the
capacity for synthesis and conservation of both the parent and the
derived
long-chain polyunsaturates. For instance, despite the existence of the
pathway
for synthesis of docosahexaenoate from alpha-linolenate, the former
would be
more correctly classified as 'conditionally indispensable' because the
capacity
of the pathway appears insufficient during early development, although
it may be
sufficient later in life in healthy individuals. Similarly, despite the
inability to synthesize linoleate de novo, abundant linoleate stores
and its
relatively slow turnover in healthy adults probably makes linoleate
'conditionally dispensable' for long periods. There are two other
anomalies with
the terms essential and non-essential fatty acids: (1) under several
different
experimental circumstances, the C-skeleton of essential fatty acids is
avidly
used in the synthesis of non-essential fatty acids; (2) to function
normally,
the brain is required to endogenously synthesize several non-essential
fatty
acids. As with essential amino acids, which have been reclassified as
indispensable or conditionally indispensable, such a change in
terminology
should lead to an improved understanding of the function and metabolism
of
polyunsaturates in particular, and long-chain fatty acids in general.

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PMID: 11177196 [PubMed - indexed for MEDLINE]

J Nutr Health Aging. 2004;8(3):163-74.

Roles of unsaturated fatty acids (especially omega-3 fatty acids) in
the brain
at various ages and during ageing.

Bourre JM.

INSERM Research Director. Unit U26 Neuro-pharmaco-nutrition. Hopital
Fernand
Widal, 200 rue du Faubourg Saint Denis. 75745 Paris cedex 10.
jean-marie.bourre@fwidal.inserm.fr

Among various organs, in the brain, the fatty acids most extensively
studied are
omega-3 fatty acids. Alpha-linolenic acid (18:3omega3) deficiency
alters the
structure and function of membranes and induces minor cerebral
dysfunctions, as
demonstrated in animal models and subsequently in human infants. Even
though the
brain is materially an organ like any other, that is to say elaborated
from
substances present in the diet (sometimes exclusively), for long it was
not
accepted that food can have an influence on brain structure, and thus
on its
function. Lipids, and especially omega-3 fatty acids, provided the
first
coherent experimental demonstration of the effect of diet (nutrients)
on the
structure and function of the brain. In fact the brain, after adipose
tissue, is
the organ richest in lipids, whose only role is to participate in
membrane
structure. First it was shown that the differentiation and functioning
of
cultured brain cells requires not only alpha-linolenic acid (the major
component
of the omega-3, omega3 family), but also the very long omega-3 and
omega-6
carbon chains (1). It was then demonstrated that alpha-linolenic acid
deficiency
alters the course of brain development, perturbs the composition and
physicochemical properties of brain cell membranes, neurones,
oligodendrocytes,
and astrocytes (2).This leads to physicochemical modifications, induces
biochemical and physiological perturbations, and results in
neurosensory and
behavioural upset (3). Consequently, the nature of polyunsaturated
fatty acids
(in particular omega-3) present in formula milks for infants (premature
and
term) conditions the visual and cerebral abilities, including
intellectual.
Moreover, dietary omega-3 fatty acids are certainly involved in the
prevention
of some aspects of cardiovascular disease (including at the level of
cerebral
vascularization), and in some neuropsychiatric disorders, particularly
depression, as well as in dementia, notably Alzheimer's disease. Recent
results
have shown that dietary alpha-linolenic acid deficiency induces more
marked
abnormalities in certain cerebral structures than in others, as the
frontal
cortex and pituitary gland are more severely affected. These selective
lesions
are accompanied by behavioural disorders more particularly affecting
certain
tests (habituation, adaptation to new situations). Biochemical and
behavioural
abnormalities are partially reversed by a dietary phospholipid
supplement,
especially omega-3-rich egg yolk extracts or pig brain. A dose-effect
study
showed that animal phospholipids are more effective than plant
phospholipids to
reverse the consequences of alpha-linolenic acid deficiency, partly
because they
provide very long preformed chains. Alpha-linolenic acid deficiency
decreases
the perception of pleasure, by slightly altering the efficacy of
sensory organs
and by affecting certain cerebral structures. Age-related impairment of
hearing,
vision and smell is due to both decreased efficacy of the parts of the
brain
concerned and disorders of sensory receptors, particularly of the inner
ear or
retina. For example, a given level of perception of a sweet taste
requires a
larger quantity of sugar in subjects with alpha-linolenic acid
deficiency. In
view of occidental eating habits, as omega-6 fatty acid deficiency has
never
been observed, its impact on the brain has not been studied. In
contrast,
omega-9 fatty acid deficiency, specifically oleic acid deficiency,
induces a
reduction of this fatty acid in many tissues, except the brain (but the
sciatic
nerve is affected). This fatty acid is therefore not synthesized in
sufficient
quantities, at least during pregnancy-lactation, implying a need for
dietary
intake. It must be remembered that organization of the neurons is
almost
complete several weeks before birth, and that these neurons remain for
the
subject's life time. Consequently, any disturbance of these neurons, an
alteration of their connections, and impaired turnover of their
constituents at
any stage of life, will tend to accelerate ageing. The enzymatic
activities of
sytivities of synthesis of long-chain polyunsaturated fatty acids from
linoleic
and alpha-linolenic acids are very limited in the brain: this organ
therefore
depends on an exogenous supply. Consequently, fatty acids that are
essential for
the brain are arachidonic acid and cervonic acid, derived from the
diet, unless
they are synthesized by the liver from linoleic acid and
alpha-linolenic acid.
The age-related reduction of hepatic desaturase activities (which
participate in
the synthesis of long chains, together with elongases) can impair
turnover of
cerebral membranes. In many structures, especially in the frontal
cortex, a
reduction of cervonic and arachidonic acids is observed during ageing,
predominantly associated with a reduction of phosphatidylethanolamines
(mainly
in the form of plasmalogens). Peroxisomal oxidation of polyunsaturated
fatty
acids decreases in the brain during ageing, participating in decreased
turnover
of membrane fatty acids, which are also less effectively protected
against
peroxidation by free radicals.

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PMID: 15129302 [PubMed - indexed for MEDLINE]

J Nutr. 1998 Feb;128(2 Suppl):427S-433S.

Comment in:
   J Nutr. 1999 Feb;129(2):446.

The slow discovery of the importance of omega 3 essential fatty acids
in human
health.

Holman RT.

Hormel Institute, University of Minnesota, Austin 55912, USA.

Although linoleic and linolenic acids have been known to be necessary
for normal
growth and dermal function since 1930, the omega 3 essential fatty
acids (EFA)
have not received much attention until recently. The two families of
acids are
metabolized by the same enzymes, making them competitive. Gross
deficiencies of
omega 6 plus omega 3 EFA have been observed in humans, induced by
attempts at
total parenteral nutrition (TPN) with preparations devoid of lipids.
Deficiency
of omega 3 acids has been induced by TPN containing high omega 6 and
low omega 3
fatty acids. In natural human populations, a wide range of omega 3 and
omega 6
proportions have been found, ranging from high omega 3 and low omega 6
content
to low omega 3 and high omega 6 content, showing inverse correlation
between
sigma omega 6 and sigma omega 3. In humans with neuropathy or
impairment of the
immune system, significant deficits of omega 3 EFA have been measured.

Publication Types:
   Review
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PMID: 9478042 [PubMed - indexed for MEDLINE]

Curr Opin Clin Nutr Metab Care. 2002 Mar;5(2):127-32.

Efficiency of conversion of alpha-linolenic acid to long chain n-3
fatty acids
in man.

Brenna JT.

Division of Nutritional Sciences, Savage Hall, Cornell University,
Ithaca, New
York 14853, USA. jtb4@cornell.edu

Alpha-linolenic acid (18:3n-3) is the major n-3 (omega 3) fatty acid in
the
human diet. It is derived mainly from terrestrial plant consumption and
it has
long been thought that its major biochemical role is as the principal
precursor
for long chain polyunsaturated fatty acids, of which eicosapentaenoic
(20:5n-3)
and docosahexaenoic acid (22:6n-3) are the most prevalent. For infants,
n-3 long
chain polyunsaturated fatty acids are required for rapid growth of
neural tissue
in the perinatal period and a nutritional supply is particularly
important for
development of premature infants. For adults, n-3 long chain
polyunsaturated
fatty acid supplementation is implicated in improving a wide range of
clinical
pathologies involving cardiac, kidney, and neural tissues. Studies
generally
agree that whole body conversion of 18:3n-3 to 22:6n-3 is below 5% in
humans,
and depends on the concentration of n-6 fatty acids and long chain
polyunsaturated fatty acids in the diet. Complete oxidation of dietary
18:3n-3
to CO2 accounts for about 25% of 18:3n-3 in the first 24 h, reaching
60% by 7
days. Much of the remaining 18:3n-3 serves as a source of acetate for
synthesis
of saturates and monounsaturates, with very little stored as 18:3n-3.
In term
and preterm infants, studies show wide variability in the plasma
kinetics of 13C
n-3 long chain polyunsaturated fatty acids after 13C-18:3n-3 dosing,
suggesting
wide variability among human infants in the development of biosynthetic
capability to convert 18:3n-3 to 22:6n3. Tracer studies show that
humans of all
ages can perform the conversion of 18:3n-3 to 22:6n3. Further studies
are
required to establish quantitatively the partitioning of dietary
18:3n-3 among
metabolic pathways and the influence of other dietary components and of
physiological states on these processes.

Publication Types:
   Review
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PMID: 11844977 [PubMed - indexed for MEDLINE]

Annu Rev Nutr. 2004;24:597-615.

Dietary n-6 and n-3 fatty acid balance and cardiovascular health.

Wijendran V, Hayes KC.

Foster Biomedical Research Lab, Brandeis University, Waltham,
Massachusetts
02254, USA. vwijen@brandeis.edu

Epidemiological and clinical studies have established that the n-6
fatty acid,
linoleic acid (LA), and the n-3 fatty acids, linolenic acid (LNA),
eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)
collectively protect
against coronary heart disease (CHD). LA is the major dietary fatty
acid
regulating low-density lipoprotein (LDL)-C metabolism by downregulating
LDL-C
production and enhancing its clearance. Further, the available mass of
LA is a
critical factor determining the hyperlipemic effects of other dietary
fat
components, such as saturated and trans fatty acids, as well as
cholesterol. By
contrast, n-3 fatty acids, especially EPA and DHA, are potent
antiarryhthmic
agents. EPA and DHA also improve vascular endothelial function and help
lower
blood pressure, platelet sensitivity, and the serum triglyceride level.
The
distinct functions of these two families make the balance between
dietary n-6
and n-3 fatty acids an important consideration influencing
cardiovascular
health. Based on published literature describing practical dietary
intakes, we
suggest that consumption of ~6% en LA, 0.75% en LNA, and 0.25% en EPA +
DHA
represents adequate and achievable intakes for most healthy adults.
This
corresponds to an n-6/n-3 ratio of ~6:1. However, the absolute mass of
essential
fatty acids consumed, rather than their n-6/n-3 ratio, should be the
first
consideration when contemplating lifelong dietary habits affecting
cardiovascular benefit from their intake.

Publication Types:
   Review

PMID: 15189133 [PubMed - indexed for MEDLINE]

What "you have been saying here for years" is ever so slightly changing..
once it was: all PUFA's are the ultimate evil..
now you slowly seem to adapt to the idea that w3's can actually be
beneficial.

Sbharris commented on this 1930's myth already. You seem to like this idea
quite a lot since you still cite yourself on that constantly.. you are not
up to date on the literature there.