The relationship between dietary alpha-linolenic:linoleic acid and rat eicosapentaenoic and arachidonic acids.
The relationship between dietary alpha-linolenic:linoleic acid and rat eicosapentaenoic and arachidonic acids.
Year: 1996
Authors: E A Leece, M A Allman.
Publication Name: Brit. J. Nutr.
Publication Details: Volume 76; Page 447.
Abstract:
Competition between n-3 and n-6 fatty acids for enzymes involved in elongation and subsequent desaturation will determine the relative proportions of long chain PUFAs that can be synthesized in humans. Previous research has indicated that the dietary ratio of ALA:LA, rather the absolute amount of ALA, influences EPA incorporation into tissue PLs. However, controversy exists regarding the ideal dietary amounts of ALA and LA that should be consumed as various ratios of these two fatty acids have been studied. The aim of the present research was to examine the effects of altering the dietary ALA:LA ratio on rat platelet EPA and AA concentrations. Rats were fed diets containing 30% total energy as fat with approximately 10% each of SFA, MUFA and PUFA. Diets contained one of the following ALA:LA values: 1:7, 1:4, 1:1 or 1.3:1 (nine rats per group). These diets were chosen because they would be achievable in human mixed diets based on 30% of total energy as fat with 10% from SFA and 10% from PUFA. Rats were used because they have the same enzyme pathways as humans for elongation and desaturation of ALA to EPA. After 4 weeks, the ratio of platelet EPA:ALA increased in a linear fashion as rats were fed diets with increasing ALA:LA ratios. The EPA level in platelet PLs was significantly greater at the 1:1 and 1.3:1 ratios compared with the 1:7 and 1:4. A significant decrease in platelet AA was observed at the higher dietary ratios. It was established that the ratio of platelet EPA:AA increased significantly as the dietary ALA:LA value increased. The authors noted that, although these findings can not be applied directly to humans, they do suggest that the inclusion of dietary oils such as flaxseed oil with moderate ALA:LA ratios should result in significant EPA enrichment and an increase in the EPA:AA ratio in tissue PLs. However, the dietary ratio of ALA:LA required to produce maximal concentrations of EPA requires further investigation as does the level of EPA:AA in platelets which would provide beneficial biological effects.
