Posted by Larry Hoover on October 17, 2003, at 9:06:50
In reply to Omega3 - Fish Oil or Flaxseed Oil?, posted by rianny on October 15, 2003, at 22:50:47
> It seems like both contain Omega3, but I'd like to know if they have the same effect when consumed.
No, they don't. Omega-3 is a category of fatty acids, within which are a number of biochemically distinct molecules. Flaxseed oil contains high concentrations of alpha-linolenic acid (ALNA), an eighteen carbon fatty acid with three unsaturated positions, one of which is in the omega-3 position. Fish oil has a little bit of alpha-linolenic acid, but it contains much higher concentrations of eicosapentaenoic acid, (EPA, twenty carbons, five times desaturated), and docosahexaenoic acid (DHA, twenty-two carbons, six unsaturated). It was once believed that dietary sources of ALA were sufficient to produce the necessary amounts of EPA and DHA, via enzymatic elongation and desaturation, but recent research has shown that assumption to be false, particularly if you're of the male gender. From the first abstract: "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." Even for females, conversion to DHA did not exceed 9%, so it still makes sense to obtain EPA and DHA from diet, e.g. fish, or omega-enhanced eggs, or free-range meat.
Br J Nutr. 2002 Oct;88(4):355-63.
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. gcb@soton.ac.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):411-20.
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. g.c.burdge@soton.ac.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) micromol/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) micromol/l) and CE (42 (sem 9) micromol/l) over 21 d. In contrast both [13C]DPA and [13C]DHA were detected predominately in PC (18 (sem 4) and 27 (sem 7) micromol/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.
> Also, please recommend the best brand of Fish Oil. There are too many, and I don't know which one to try.For price and quality, I don't think you can beat the Walmart or Sam's Club or Costco house-brand products.
Lar
poster:Larry Hoover
thread:269861
URL: http://www.dr-bob.org/babble/alter/20031003/msgs/270167.html