w3 conversion into EPA/DHA

"andrewvecsey" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

It is stated in many references that the body converts w3 into EPA/DHA
"inefficiently" but they never say how efficient the conversion is.
Can any one lead me to some answers?
regards
andrew vecsey
http://geocities.com/andrewvecsey/omega3.html

From the first abstract (ALNA is alpha-linolenic acid, the omega-3 in flax
oil; DHA is the longer chained omega-3 in fish oil):

"Since the capacity of adult males to convert ALNA to DHA was either very
low or absent, uptake of pre-formed DHA from the diet may be critical for
maintaining adequate membrane DHA concentrations in these individuals."

Young men, ALA to DHA, 0%. (first abstract)
Young women, ALA to DHA, 9%. (second abstract)
The third abstract considers the effect of other fatty acid intake on conversion.

Br J Nutr 2002 Oct;88(4):355-64

Eicosapentaenoic and docosapentaenoic acids are the principal products of
alpha-linolenic acid metabolism in young men*.

Burdge GC, Jones AE, Wootton SA.

Institute of Human Nutrition, Level C, West Wing, Southampton General
Hospital, Tremona Road, Southampton, SO16 6YD, UK.

The capacity for conversion of alpha-linolenic acid (ALNA) to n-3 long-chain
polyunsaturated fatty acids was investigated in young men. Emulsified
[U-13C]ALNA was administered orally with a mixed meal to six subjects
consuming their habitual diet. Approximately 33 % of administered [13C]ALNA
was recovered as 13CO2 on breath over the first 24 h. [13C]ALNA was
mobilised from enterocytes primarily as chylomicron triacylglycerol (TAG),
while [13C]ALNA incorporation into plasma phosphatidylcholine (PC) occurred
later, probably by the liver. The time scale of conversion of [13C]ALNA to
eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA) suggested that
the liver was the principal site of ALNA desaturation and elongation,
although there was some indication of EPA and DPA synthesis by enterocytes.
[13C]EPA and [13C]DPA concentrations were greater in plasma PC than TAG, and
were present in the circulation for up to 7 and 14 d, respectively. There
was no apparent 13C enrichment of docosahexaenoic acid (DHA) in plasma PC,
TAG or non-esterified fatty acids at any time point measured up to 21 d.
This pattern of 13C n-3 fatty acid labelling suggests inhibition or
restriction of DHA synthesis downstream of DPA. [13C]ALNA, [13C]EPA and
[13C]DPA were incorporated into erythrocyte PC, but not
phosphatidylethanolamine, suggesting uptake of intact plasma PC molecules
from lipoproteins into erythrocyte membranes. Since the capacity of adult
males to convert ALNA to DHA was either very low or absent, uptake of
pre-formed DHA from the diet may be critical for maintaining adequate
membrane DHA concentrations in these individuals.

Br J Nutr 2002 Oct;88(4):411-421

Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and
docosahexaenoic acids in young women.

Burdge GC, Wootton SA.

Institute of Human Nutrition, University of Southampton, Southampton, UK.

The extent to which women of reproductive age are able to convert the n-3
fatty acid alpha-linolenic acid (ALNA) to eicosapentaenoic acid (EPA),
docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) was investigated
in vivo by measuring the concentrations of labelled fatty acids in plasma
for 21 d following the ingestion of [U-13C]ALNA (700 mg). [13C]ALNA
excursion was greatest in cholesteryl ester (CE) (224 (sem 70) &mgr;mol/l
over 21 d) compared with triacylglycerol (9-fold), non-esterified fatty
acids (37-fold) and phosphatidylcholine (PC, 7-fold). EPA excursion was
similar in both PC (42 (sem 8) &mgr;mol/l) and CE (42 (sem 9) &mgr;mol/l)
over 21 d. In contrast both [13C]DPA and [13C]DHA were detected
predominately in PC (18 (sem 4) and 27 (sem 7) &mgr;mol/l over 21 d,
respectively). Estimated net fractional ALNA inter-conversion was EPA 21 %,
DPA 6 % and DHA 9 %. Approximately 22 % of administered [13C]ALNA was
recovered as 13CO2 on breath over the first 24 h of the study. These results
suggest differential partitioning of ALNA, EPA and DHA between plasma lipid
classes, which may facilitate targeting of individual n-3 fatty acids to
specific tissues. Comparison with previous studies suggests that women may
possess a greater capacity for ALNA conversion than men. Such metabolic
capacity may be important for meeting the demands of the fetus and neonate
for DHA during pregnancy and lactation. Differences in DHA status between
women both in the non-pregnant state and in pregnancy may reflect variations
in metabolic capacity for DHA synthesis.

Int J Vitam Nutr Res 1998;68(3):159-73

Can adults adequately convert alpha-linolenic acid (18:3n-3) to
eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)?

Gerster H.

Vitamin Research Department, F. Hoffman-Roche Ltd, Basel, Switzerland.

A diet including 2-3 portions of fatty fish per week, which corresponds to
the intake of 1.25 g EPA (20:5n-3) + DHA (22:6n-3) per day, has been
officially recommended on the basis of epidemiological findings showing a
beneficial role of these n-3 long-chain PUFA in the prevention of
cardiovascular and inflammatory diseases. The parent fatty acid ALA
(18:3n-3), found in vegetable oils such as flaxseed or rapeseed oil, is used
by the human organism partly as a source of energy, partly as a precursor of
the metabolites, but the degree of conversion appears to be unreliable and
restricted. More specifically, most studies in humans have shown that
whereas a certain, though restricted, conversion of high doses of ALA to EPA
occurs, conversion to DHA is severely restricted. The use of ALA labelled
with radioisotopes suggested that with a background diet high in saturated
fat conversion to long-chain metabolites is approximately 6% for EPA and
3.8% for DHA. With a diet rich in n-6 PUFA, conversion is reduced by 40 to
50%. It is thus reasonable to observe an n-6/n-3 PUFA ratio not exceeding
4-6. Restricted conversion to DHA may be critical since evidence has been
increasing that this long-chain metabolite has an autonomous function, e.g.
in the brain, retina and spermatozoa where it is the most prominent fatty
acid. In neonates deficiency is associated with visual impairment,
abnormalities in the electroretinogram and delayed cognitive development. In
adults the potential role of DHA in neurological function still needs to be
investigated in depth. Regarding cardiovascular risk factors DHA has been
shown to reduce triglyceride concentrations. These findings indicate that
future attention will have to focus on the adequate provision of DHA which
can reliably be achieved only with the supply of the preformed long-chain
metabolite.

"Larry Hoover" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"andrewvecsey" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

It is stated in many references that the body converts w3 into
EPA/DHA
"inefficiently" but they never say how efficient the conversion
is.
Can any one lead me to some answers?
regards
andrew vecsey
http://geocities.com/andrewvecsey/omega3.html

From the first abstract (ALNA is alpha-linolenic acid, the omega-3
in flax
oil; DHA is the longer chained omega-3 in fish oil):

"Since the capacity of adult males to convert ALNA to DHA was
either very
low or absent, uptake of pre-formed DHA from the diet may be
critical for
maintaining adequate membrane DHA concentrations in these
individuals."

Young men, ALA to DHA, 0%. (first abstract)
Young women, ALA to DHA, 9%. (second abstract)
The third abstract considers the effect of other fatty acid intake
on conversion.

Br J Nutr 2002 Oct;88(4):355-64

Eicosapentaenoic and docosapentaenoic acids are the principal
products of
alpha-linolenic acid metabolism in young men*.

Burdge GC, Jones AE, Wootton SA.

Institute of Human Nutrition, Level C, West Wing, Southampton
General
Hospital, Tremona Road, Southampton, SO16 6YD, UK.

The capacity for conversion of alpha-linolenic acid (ALNA) to n-3
long-chain
polyunsaturated fatty acids was investigated in young men.
Emulsified
[U-13C]ALNA was administered orally with a mixed meal to six
subjects
consuming their habitual diet. Approximately 33 % of administered
[13C]ALNA
was recovered as 13CO2 on breath over the first 24 h. [13C]ALNA
was
mobilised from enterocytes primarily as chylomicron
triacylglycerol (TAG),
while [13C]ALNA incorporation into plasma phosphatidylcholine (PC)
occurred
later, probably by the liver. The time scale of conversion of
[13C]ALNA to
eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA)
suggested that
the liver was the principal site of ALNA desaturation and
elongation,
although there was some indication of EPA and DPA synthesis by
enterocytes.
[13C]EPA and [13C]DPA concentrations were greater in plasma PC
than TAG, and
were present in the circulation for up to 7 and 14 d,
respectively. There
was no apparent 13C enrichment of docosahexaenoic acid (DHA) in
plasma PC,
TAG or non-esterified fatty acids at any time point measured up to
21 d.
This pattern of 13C n-3 fatty acid labelling suggests inhibition
or
restriction of DHA synthesis downstream of DPA. [13C]ALNA,
[13C]EPA and
[13C]DPA were incorporated into erythrocyte PC, but not
phosphatidylethanolamine, suggesting uptake of intact plasma PC
molecules
from lipoproteins into erythrocyte membranes. Since the capacity
of adult
males to convert ALNA to DHA was either very low or absent, uptake
of
pre-formed DHA from the diet may be critical for maintaining
adequate
membrane DHA concentrations in these individuals.

Br J Nutr 2002 Oct;88(4):411-421

Conversion of alpha-linolenic acid to eicosapentaenoic,
docosapentaenoic and
docosahexaenoic acids in young women.

Burdge GC, Wootton SA.

Institute of Human Nutrition, University of Southampton,
Southampton, UK.

The extent to which women of reproductive age are able to convert
the n-3
fatty acid alpha-linolenic acid (ALNA) to eicosapentaenoic acid
(EPA),
docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) was
investigated
in vivo by measuring the concentrations of labelled fatty acids in
plasma
for 21 d following the ingestion of [U-13C]ALNA (700 mg).
[13C]ALNA
excursion was greatest in cholesteryl ester (CE) (224 (sem 70)
&mgr;mol/l
over 21 d) compared with triacylglycerol (9-fold), non-esterified
fatty
acids (37-fold) and phosphatidylcholine (PC, 7-fold). EPA
excursion was
similar in both PC (42 (sem 8) &mgr;mol/l) and CE (42 (sem 9)
&mgr;mol/l)
over 21 d. In contrast both [13C]DPA and [13C]DHA were detected
predominately in PC (18 (sem 4) and 27 (sem 7) &mgr;mol/l over 21
d,
respectively). Estimated net fractional ALNA inter-conversion was
EPA 21 %,
DPA 6 % and DHA 9 %. Approximately 22 % of administered [13C]ALNA
was
recovered as 13CO2 on breath over the first 24 h of the study.
These results
suggest differential partitioning of ALNA, EPA and DHA between
plasma lipid
classes, which may facilitate targeting of individual n-3 fatty
acids to
specific tissues. Comparison with previous studies suggests that
women may
possess a greater capacity for ALNA conversion than men. Such
metabolic
capacity may be important for meeting the demands of the fetus and
neonate
for DHA during pregnancy and lactation. Differences in DHA status
between
women both in the non-pregnant state and in pregnancy may reflect
variations
in metabolic capacity for DHA synthesis.

Int J Vitam Nutr Res 1998;68(3):159-73

Can adults adequately convert alpha-linolenic acid (18:3n-3) to
eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid
(22:6n-3)?

Gerster H.

Vitamin Research Department, F. Hoffman-Roche Ltd, Basel,
Switzerland.

A diet including 2-3 portions of fatty fish per week, which
corresponds to
the intake of 1.25 g EPA (20:5n-3) + DHA (22:6n-3) per day, has
been
officially recommended on the basis of epidemiological findings
showing a
beneficial role of these n-3 long-chain PUFA in the prevention of
cardiovascular and inflammatory diseases. The parent fatty acid
ALA
(18:3n-3), found in vegetable oils such as flaxseed or rapeseed
oil, is used
by the human organism partly as a source of energy, partly as a
precursor of
the metabolites, but the degree of conversion appears to be
unreliable and
restricted. More specifically, most studies in humans have shown
that
whereas a certain, though restricted, conversion of high doses of
ALA to EPA
occurs, conversion to DHA is severely restricted. The use of ALA
labelled
with radioisotopes suggested that with a background diet high in
saturated
fat conversion to long-chain metabolites is approximately 6% for
EPA and
3.8% for DHA. With a diet rich in n-6 PUFA, conversion is reduced
by 40 to
50%. It is thus reasonable to observe an n-6/n-3 PUFA ratio not
exceeding
4-6. Restricted conversion to DHA may be critical since evidence
has been
increasing that this long-chain metabolite has an autonomous
function, e.g.
in the brain, retina and spermatozoa where it is the most
prominent fatty
acid. In neonates deficiency is associated with visual impairment,
abnormalities in the electroretinogram and delayed cognitive
development. In
adults the potential role of DHA in neurological function still
needs to be
investigated in depth. Regarding cardiovascular risk factors DHA
has been
shown to reduce triglyceride concentrations. These findings
indicate that
future attention will have to focus on the adequate provision of
DHA which
can reliably be achieved only with the supply of the preformed
long-chain
metabolite.

Thanks for an excellent response to an important question.
The following reference illustrates the metabolic 'competition'
between omega 3 and omega 6 PUFA which greatly influences the
process.
http://www.fatsoflife.com/intro_7.html

MikeV

Thanks for your detailed answer. I suppose one can interpret the
results many different ways. I would like to maintain my confidance
that a healthy body designed to produce DHA from ALA would do so
whenever it needed, even at a low efficiency. I would like to
interpret the results "Young men, ALA to DHA, 0%. (first abstract)" as
that it was not 0% efficiency, but instead that for these young men,
their bodies did not need at the time of the tests to convert any ALA
to DHA, because it had enough DHA. It would be disappointing, but
revealing to hear that these young men were suffering fron DHA
deficiency at the time of the test.
regards
andrew

"Larry Hoover" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"andrewvecsey" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

It is stated in many references that the body converts w3 into EPA/DHA
"inefficiently" but they never say how efficient the conversion is.
Can any one lead me to some answers?
regards
andrew vecsey
http://geocities.com/andrewvecsey/omega3.html

From the first abstract (ALNA is alpha-linolenic acid, the omega-3 in flax
oil; DHA is the longer chained omega-3 in fish oil):

"Since the capacity of adult males to convert ALNA to DHA was either very
low or absent, uptake of pre-formed DHA from the diet may be critical for
maintaining adequate membrane DHA concentrations in these individuals."

Young men, ALA to DHA, 0%. (first abstract)
Young women, ALA to DHA, 9%. (second abstract)
The third abstract considers the effect of other fatty acid intake on conversion.

Br J Nutr 2002 Oct;88(4):355-64

Eicosapentaenoic and docosapentaenoic acids are the principal products of
alpha-linolenic acid metabolism in young men*.

Burdge GC, Jones AE, Wootton SA.

Institute of Human Nutrition, Level C, West Wing, Southampton General
Hospital, Tremona Road, Southampton, SO16 6YD, UK.

The capacity for conversion of alpha-linolenic acid (ALNA) to n-3 long-chain
polyunsaturated fatty acids was investigated in young men. Emulsified
[U-13C]ALNA was administered orally with a mixed meal to six subjects
consuming their habitual diet. Approximately 33 % of administered [13C]ALNA
was recovered as 13CO2 on breath over the first 24 h. [13C]ALNA was
mobilised from enterocytes primarily as chylomicron triacylglycerol (TAG),
while [13C]ALNA incorporation into plasma phosphatidylcholine (PC) occurred
later, probably by the liver. The time scale of conversion of [13C]ALNA to
eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA) suggested that
the liver was the principal site of ALNA desaturation and elongation,
although there was some indication of EPA and DPA synthesis by enterocytes.
[13C]EPA and [13C]DPA concentrations were greater in plasma PC than TAG, and
were present in the circulation for up to 7 and 14 d, respectively. There
was no apparent 13C enrichment of docosahexaenoic acid (DHA) in plasma PC,
TAG or non-esterified fatty acids at any time point measured up to 21 d.
This pattern of 13C n-3 fatty acid labelling suggests inhibition or
restriction of DHA synthesis downstream of DPA. [13C]ALNA, [13C]EPA and
[13C]DPA were incorporated into erythrocyte PC, but not
phosphatidylethanolamine, suggesting uptake of intact plasma PC molecules
from lipoproteins into erythrocyte membranes. Since the capacity of adult
males to convert ALNA to DHA was either very low or absent, uptake of
pre-formed DHA from the diet may be critical for maintaining adequate
membrane DHA concentrations in these individuals.

Br J Nutr 2002 Oct;88(4):411-421

Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and
docosahexaenoic acids in young women.

Burdge GC, Wootton SA.

Institute of Human Nutrition, University of Southampton, Southampton, UK.

The extent to which women of reproductive age are able to convert the n-3
fatty acid alpha-linolenic acid (ALNA) to eicosapentaenoic acid (EPA),
docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) was investigated
in vivo by measuring the concentrations of labelled fatty acids in plasma
for 21 d following the ingestion of [U-13C]ALNA (700 mg). [13C]ALNA
excursion was greatest in cholesteryl ester (CE) (224 (sem 70) &mgr;mol/l
over 21 d) compared with triacylglycerol (9-fold), non-esterified fatty
acids (37-fold) and phosphatidylcholine (PC, 7-fold). EPA excursion was
similar in both PC (42 (sem 8) &mgr;mol/l) and CE (42 (sem 9) &mgr;mol/l)
over 21 d. In contrast both [13C]DPA and [13C]DHA were detected
predominately in PC (18 (sem 4) and 27 (sem 7) &mgr;mol/l over 21 d,
respectively). Estimated net fractional ALNA inter-conversion was EPA 21 %,
DPA 6 % and DHA 9 %. Approximately 22 % of administered [13C]ALNA was
recovered as 13CO2 on breath over the first 24 h of the study. These results
suggest differential partitioning of ALNA, EPA and DHA between plasma lipid
classes, which may facilitate targeting of individual n-3 fatty acids to
specific tissues. Comparison with previous studies suggests that women may
possess a greater capacity for ALNA conversion than men. Such metabolic
capacity may be important for meeting the demands of the fetus and neonate
for DHA during pregnancy and lactation. Differences in DHA status between
women both in the non-pregnant state and in pregnancy may reflect variations
in metabolic capacity for DHA synthesis.

Int J Vitam Nutr Res 1998;68(3):159-73

Can adults adequately convert alpha-linolenic acid (18:3n-3) to
eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)?

Gerster H.

Vitamin Research Department, F. Hoffman-Roche Ltd, Basel, Switzerland.

A diet including 2-3 portions of fatty fish per week, which corresponds to
the intake of 1.25 g EPA (20:5n-3) + DHA (22:6n-3) per day, has been
officially recommended on the basis of epidemiological findings showing a
beneficial role of these n-3 long-chain PUFA in the prevention of
cardiovascular and inflammatory diseases. The parent fatty acid ALA
(18:3n-3), found in vegetable oils such as flaxseed or rapeseed oil, is used
by the human organism partly as a source of energy, partly as a precursor of
the metabolites, but the degree of conversion appears to be unreliable and
restricted. More specifically, most studies in humans have shown that
whereas a certain, though restricted, conversion of high doses of ALA to EPA
occurs, conversion to DHA is severely restricted. The use of ALA labelled
with radioisotopes suggested that with a background diet high in saturated
fat conversion to long-chain metabolites is approximately 6% for EPA and
3.8% for DHA. With a diet rich in n-6 PUFA, conversion is reduced by 40 to
50%. It is thus reasonable to observe an n-6/n-3 PUFA ratio not exceeding
4-6. Restricted conversion to DHA may be critical since evidence has been
increasing that this long-chain metabolite has an autonomous function, e.g.
in the brain, retina and spermatozoa where it is the most prominent fatty
acid. In neonates deficiency is associated with visual impairment,
abnormalities in the electroretinogram and delayed cognitive development. In
adults the potential role of DHA in neurological function still needs to be
investigated in depth. Regarding cardiovascular risk factors DHA has been
shown to reduce triglyceride concentrations. These findings indicate that
future attention will have to focus on the adequate provision of DHA which
can reliably be achieved only with the supply of the preformed long-chain
metabolite.

On Mon, 22 Nov 2004 12:27:07 -0500, "Larry Hoover"
<[email hidden]> posted:

Quoted message said:

"andrewvecsey" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

It is stated in many references that the body converts w3 into EPA/DHA
"inefficiently" but they never say how efficient the conversion is.
Can any one lead me to some answers?
regards
andrew vecsey
http://geocities.com/andrewvecsey/omega3.html

From the first abstract (ALNA is alpha-linolenic acid, the omega-3 in flax
oil; DHA is the longer chained omega-3 in fish oil):

"Since the capacity of adult males to convert ALNA to DHA was either very
low or absent, uptake of pre-formed DHA from the diet may be critical for
maintaining adequate membrane DHA concentrations in these individuals."

Young men, ALA to DHA, 0%. (first abstract)
Young women, ALA to DHA, 9%. (second abstract)
The third abstract considers the effect of other fatty acid intake on conversion.

Br J Nutr 2002 Oct;88(4):355-64

Eicosapentaenoic and docosapentaenoic acids are the principal products of
alpha-linolenic acid metabolism in young men*.

Burdge GC, Jones AE, Wootton SA.

Institute of Human Nutrition, Level C, West Wing, Southampton General
Hospital, Tremona Road, Southampton, SO16 6YD, UK.

The capacity for conversion of alpha-linolenic acid (ALNA) to n-3 long-chain
polyunsaturated fatty acids was investigated in young men. Emulsified
[U-13C]ALNA was administered orally with a mixed meal to six subjects
consuming their habitual diet. Approximately 33 % of administered [13C]ALNA
was recovered as 13CO2 on breath over the first 24 h. [13C]ALNA was
mobilised from enterocytes primarily as chylomicron triacylglycerol (TAG),
while [13C]ALNA incorporation into plasma phosphatidylcholine (PC) occurred
later, probably by the liver. The time scale of conversion of [13C]ALNA to
eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA) suggested that
the liver was the principal site of ALNA desaturation and elongation,
although there was some indication of EPA and DPA synthesis by enterocytes.
[13C]EPA and [13C]DPA concentrations were greater in plasma PC than TAG, and
were present in the circulation for up to 7 and 14 d, respectively. There
was no apparent 13C enrichment of docosahexaenoic acid (DHA) in plasma PC,
TAG or non-esterified fatty acids at any time point measured up to 21 d.
This pattern of 13C n-3 fatty acid labelling suggests inhibition or
restriction of DHA synthesis downstream of DPA. [13C]ALNA, [13C]EPA and
[13C]DPA were incorporated into erythrocyte PC, but not
phosphatidylethanolamine, suggesting uptake of intact plasma PC molecules
from lipoproteins into erythrocyte membranes. Since the capacity of adult
males to convert ALNA to DHA was either very low or absent, uptake of
pre-formed DHA from the diet may be critical for maintaining adequate
membrane DHA concentrations in these individuals.

Br J Nutr 2002 Oct;88(4):411-421

Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and
docosahexaenoic acids in young women.

Burdge GC, Wootton SA.

Institute of Human Nutrition, University of Southampton, Southampton, UK.

The extent to which women of reproductive age are able to convert the n-3
fatty acid alpha-linolenic acid (ALNA) to eicosapentaenoic acid (EPA),
docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) was investigated
in vivo by measuring the concentrations of labelled fatty acids in plasma
for 21 d following the ingestion of [U-13C]ALNA (700 mg). [13C]ALNA
excursion was greatest in cholesteryl ester (CE) (224 (sem 70) &mgr;mol/l
over 21 d) compared with triacylglycerol (9-fold), non-esterified fatty
acids (37-fold) and phosphatidylcholine (PC, 7-fold). EPA excursion was
similar in both PC (42 (sem 8) &mgr;mol/l) and CE (42 (sem 9) &mgr;mol/l)
over 21 d. In contrast both [13C]DPA and [13C]DHA were detected
predominately in PC (18 (sem 4) and 27 (sem 7) &mgr;mol/l over 21 d,
respectively). Estimated net fractional ALNA inter-conversion was EPA 21 %,
DPA 6 % and DHA 9 %. Approximately 22 % of administered [13C]ALNA was
recovered as 13CO2 on breath over the first 24 h of the study. These results
suggest differential partitioning of ALNA, EPA and DHA between plasma lipid
classes, which may facilitate targeting of individual n-3 fatty acids to
specific tissues. Comparison with previous studies suggests that women may
possess a greater capacity for ALNA conversion than men. Such metabolic
capacity may be important for meeting the demands of the fetus and neonate
for DHA during pregnancy and lactation. Differences in DHA status between
women both in the non-pregnant state and in pregnancy may reflect variations
in metabolic capacity for DHA synthesis.

Int J Vitam Nutr Res 1998;68(3):159-73

Can adults adequately convert alpha-linolenic acid (18:3n-3) to
eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)?

Gerster H.

Vitamin Research Department, F. Hoffman-Roche Ltd, Basel, Switzerland.

A diet including 2-3 portions of fatty fish per week, which corresponds to
the intake of 1.25 g EPA (20:5n-3) + DHA (22:6n-3) per day, has been
officially recommended on the basis of epidemiological findings showing a
beneficial role of these n-3 long-chain PUFA in the prevention of
cardiovascular and inflammatory diseases. The parent fatty acid ALA
(18:3n-3), found in vegetable oils such as flaxseed or rapeseed oil, is used
by the human organism partly as a source of energy, partly as a precursor of
the metabolites, but the degree of conversion appears to be unreliable and
restricted. More specifically, most studies in humans have shown that
whereas a certain, though restricted, conversion of high doses of ALA to EPA
occurs, conversion to DHA is severely restricted. The use of ALA labelled
with radioisotopes suggested that with a background diet high in saturated
fat conversion to long-chain metabolites is approximately 6% for EPA and
3.8% for DHA. With a diet rich in n-6 PUFA, conversion is reduced by 40 to
50%. It is thus reasonable to observe an n-6/n-3 PUFA ratio not exceeding
4-6. Restricted conversion to DHA may be critical since evidence has been
increasing that this long-chain metabolite has an autonomous function, e.g.
in the brain, retina and spermatozoa where it is the most prominent fatty
acid. In neonates deficiency is associated with visual impairment,
abnormalities in the electroretinogram and delayed cognitive development. In
adults the potential role of DHA in neurological function still needs to be
investigated in depth. Regarding cardiovascular risk factors DHA has been
shown to reduce triglyceride concentrations. These findings indicate that
future attention will have to focus on the adequate provision of DHA which
can reliably be achieved only with the supply of the preformed long-chain
metabolite.

Yes, thanks for a fascinating response. I'm wondering what the bottom
line is here. I keep hearing about EFAs (essential fatty acids) and
can't seem to find a consistent definition of these.

The studies you quote seem to indicate that fish oils are essential to
health, and some EFAs cannot be derived from vegetable sources. Is
this how you read it? If you eat only fats from a little lean meat, a
little low fat cheese, and vegetable sources (avocado, grains and nuts
- not refined oils, but the whole food) and your fat intake is say 20%
of your calorie intake, will you likely get sufficient EFAs for good
health? I'd really appreciate your comments on this, thanks.

"Dunne E. Dawe" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Mon, 22 Nov 2004 12:27:07 -0500, "Larry Hoover"
<[email hidden]> posted:

Quoted message said:

Yes, thanks for a fascinating response. I'm wondering what the
bottom
line is here. I keep hearing about EFAs (essential fatty acids)
and
can't seem to find a consistent definition of these.

The studies you quote seem to indicate that fish oils are
essential to
health, and some EFAs cannot be derived from vegetable sources. Is
this how you read it? If you eat only fats from a little lean
meat, a
little low fat cheese, and vegetable sources (avocado, grains and
nuts
- not refined oils, but the whole food) and your fat intake is say
20%
of your calorie intake, will you likely get sufficient EFAs for
good
health? I'd really appreciate your comments on this, thanks.

This is a good review, I believe, listing 226 refs. This should
satisfy even a Mooshe. :-)

http://www.st-hs.com/TMA_Forum/PUFA%20-%20Calvani%20Benatti%20-%20Feb%202K3.pdf

MikeV

On Wed, 24 Nov 2004 05:53:46 GMT, "MikeV" <[email hidden]>
posted:

Quoted message said:

"Dunne E. Dawe" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Mon, 22 Nov 2004 12:27:07 -0500, "Larry Hoover"
<[email hidden]> posted:

Quoted message said:

Yes, thanks for a fascinating response. I'm wondering what the
bottom
line is here. I keep hearing about EFAs (essential fatty acids)
and
can't seem to find a consistent definition of these.

The studies you quote seem to indicate that fish oils are
essential to
health, and some EFAs cannot be derived from vegetable sources. Is
this how you read it? If you eat only fats from a little lean
meat, a
little low fat cheese, and vegetable sources (avocado, grains and
nuts
- not refined oils, but the whole food) and your fat intake is say
20%
of your calorie intake, will you likely get sufficient EFAs for
good
health? I'd really appreciate your comments on this, thanks.

This is a good review, I believe, listing 226 refs. This should
satisfy even a Mooshe. :-)

http://www.st-hs.com/TMA_Forum/PUFA%20-%20Calvani%20Benatti%20-%20Feb%202K3.pdf

Thanks Mike. I've printed it out to study it thoroughly.
Lots to learn! Great stuff!
By the way, what's a Mooshe? Is that an American term?

"Dunne E. Dawe" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Wed, 24 Nov 2004 05:53:46 GMT, "MikeV"
<[email hidden]>
posted:

Quoted message said:

"Dunne E. Dawe" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Mon, 22 Nov 2004 12:27:07 -0500, "Larry Hoover"
<[email hidden]> posted:

>

I'd really appreciate your comments on this, thanks.

This is a good review, I believe, listing 226 refs. This should
satisfy even a Mooshe. :-)

http://www.st-hs.com/TMA_Forum/PUFA%20-%20Calvani%20Benatti%20-%20Feb%202K3.pdf

Thanks Mike. I've printed it out to study it thoroughly.
Lots to learn! Great stuff!
By the way, what's a Mooshe? Is that an American term?

An Aussie not familiar with the Mooshe... ... ? I'd have to say that
this is roughly the equivalent of not knowing "Walting Matilda".

'The Mooshe' was a fabled but elusive "swagperson" who roamed the
outback and the news-groups around the turn of the century. (even
her/his gender was uncertain and frequently debated).
Almost never missed a chance to leave his mark, frequently derisive,
on other posters' generally inadequate posts.
Probably of Pommish origin. Definitely not your typical laid-back
Aussie.
Rumored to have been been an illegitimate off-spring of an itinerant
Oxford Don.
Style: Casting pearls to the masses.
Key words: Traditional; succinct; pedantic; simplistic;
authoritative; deluded; glycemic.

Search the google 'groups' for 'mooshe' along with almost any
scientific topic. You'll find her/him! :-)

HTH
MikeV