High Omega-6 Diet Lowers Omega-3 Status, but Low Omega-6 Diet Preserves
Bottomline: Healthy men fed a high omega-6 fat diet resulted in lower EPA blood levels, compared to those given a low omega-6 fat diet. Researchers conclude that the typical western diet, high in omega-6 fat is pro-inflammatory.
Prostaglandins, Leukotrienes and Essential Fatty Acids - April 2009: 201-206.
Background: Linoleic acid, an omega-6 fatty acid, accounts for 90% of the polyunsaturated fat consumption in western countries. There has been a dramatic increase in the food supply of omega-6 fats since the 1900s.
Linoleic acid competes with omega-3 fatty acid, alpha linolenic acid, for key enzymes, which are in limited supply. This competitive factor, combined with high intakes of dietary linoleic acid, can reduce the cellular levels of the potent omega-3 fatty acids, EPA and DHA. Consequently, this alters the balance of omega-3- and omega-6-fatty acids in the cells, which ultimately effects eicosanoid formation (leukotrienes, thromboxanes, prostaglandins, and lipoxins).
Study:This randomized cross-over study, involved 21 adult men, 20–45yr of age. They were fed either a low omega-6 fat diet (4% of total calories from linoleic acid), or a high omega-6 fat diet (10% of total calories). Both diets had 1% of calories from alpha linolenic acid, which respectively provides dietary omega-6/omega-3 ratios of 10:1 to 4:1.
An increase in linoleic acid intakes from 4% energy to 10% energy resulted in an increase in 20:2n-6 and decrease in EPA, suggesting increased metabolism of linoleic acid by direct elongation and inhibition of alpha linolenic acid conversion to EPA. Conversely, decreasing dietary linoleic acid resulted in a two-fold increase of EPA in the cells.
There was no increase in arachidonic acid, which is consistent with other findings, indicating that 3% energy linoleic acid is too high and floods the fatty acid metabolic pathway. The researchers believe that alpha linolenic acid functions to constrain linoleic acid conversion to arachidonic acid, and is most likely to be evident at linoleic acid/alpha linolenic acid ratios below 4:1.
Conclusion: Since the phospholipid arachidonic acid/EPA ratios were higher in men consuming 10% omega-6 fat diet compared to the 4% omega-6 fat, it is consistent with the concern that current western diets promote a pro-inflammatory environment.
Study Quote: “Our studies add to the concern that current intakes and recommendations for linoleic acid are high, while intakes of alpha-linoleic acid are so low as to contribute to a high tissue arachidonic acid/omega-3 fatty acids balance through suppression of omega-3 fatty acids metabolism."
Link to Study:
Y. Angela Liou and Sheila M. Innis
Dietary linoleic acid has no effect on arachidonic acid, but increases n-6 eicosadienoic acid, and lowers dihomo-γ-linolenic and eicosapentaenoic acid in plasma of adult men. Prostaglandins, Leukotrienes and Essential Fatty Acids - April 2009: 201-206.
Prostaglandins, Leukotrienes and Essential Fatty Acids - April 2009: 201-206.
Background: Linoleic acid, an omega-6 fatty acid, accounts for 90% of the polyunsaturated fat consumption in western countries. There has been a dramatic increase in the food supply of omega-6 fats since the 1900s.
Linoleic acid competes with omega-3 fatty acid, alpha linolenic acid, for key enzymes, which are in limited supply. This competitive factor, combined with high intakes of dietary linoleic acid, can reduce the cellular levels of the potent omega-3 fatty acids, EPA and DHA. Consequently, this alters the balance of omega-3- and omega-6-fatty acids in the cells, which ultimately effects eicosanoid formation (leukotrienes, thromboxanes, prostaglandins, and lipoxins).
Study:This randomized cross-over study, involved 21 adult men, 20–45yr of age. They were fed either a low omega-6 fat diet (4% of total calories from linoleic acid), or a high omega-6 fat diet (10% of total calories). Both diets had 1% of calories from alpha linolenic acid, which respectively provides dietary omega-6/omega-3 ratios of 10:1 to 4:1.
An increase in linoleic acid intakes from 4% energy to 10% energy resulted in an increase in 20:2n-6 and decrease in EPA, suggesting increased metabolism of linoleic acid by direct elongation and inhibition of alpha linolenic acid conversion to EPA. Conversely, decreasing dietary linoleic acid resulted in a two-fold increase of EPA in the cells.
There was no increase in arachidonic acid, which is consistent with other findings, indicating that 3% energy linoleic acid is too high and floods the fatty acid metabolic pathway. The researchers believe that alpha linolenic acid functions to constrain linoleic acid conversion to arachidonic acid, and is most likely to be evident at linoleic acid/alpha linolenic acid ratios below 4:1.
Conclusion: Since the phospholipid arachidonic acid/EPA ratios were higher in men consuming 10% omega-6 fat diet compared to the 4% omega-6 fat, it is consistent with the concern that current western diets promote a pro-inflammatory environment.
Study Quote: “Our studies add to the concern that current intakes and recommendations for linoleic acid are high, while intakes of alpha-linoleic acid are so low as to contribute to a high tissue arachidonic acid/omega-3 fatty acids balance through suppression of omega-3 fatty acids metabolism."
Link to Study:
Y. Angela Liou and Sheila M. Innis
Dietary linoleic acid has no effect on arachidonic acid, but increases n-6 eicosadienoic acid, and lowers dihomo-γ-linolenic and eicosapentaenoic acid in plasma of adult men. Prostaglandins, Leukotrienes and Essential Fatty Acids - April 2009: 201-206.
Posted by Evelyn Tribole MSRD at May 22, 2009 9:01 PM 
Categories: Arachidonic Acid,DHA,inflammation,ratio.,2009 Studies,omega-6/omega-3 Ratio,Diet,Cox,polyunsaturated fatty acids,Omega-6 Fat,Biomarkers,Intervention Study (Low Omega-6),Abstract
Tags: omega-6 fat omega-3 fat polyunsaturated fatty acids
Categories: Arachidonic Acid,DHA,inflammation,ratio.,2009 Studies,omega-6/omega-3 Ratio,Diet,Cox,polyunsaturated fatty acids,Omega-6 Fat,Biomarkers,Intervention Study (Low Omega-6),Abstract
Tags: omega-6 fat omega-3 fat polyunsaturated fatty acids
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