Effects of altering the ratio of dietary n-6 to n-3 fatty acids on insulin sensitivity, lipoprotein size, and postprandial lipemia in men and postmenopausal women aged 45-70 y: the OPTILIP Study.
BACKGROUND
Insulin resistance is associated with elevated plasma triacylglycerol, low HDL concentrations, elevated postprandial lipemia, and a predominance of small, dense LDLs (sdLDLs). It has been hypothesized that the dietary ratio of n-6 to n-3 (n-6:n-3) polyunsaturated fatty acids (PUFAs) may have favorable effects on these risk factors by increasing insulin sensitivity.


OBJECTIVE
The objective was to measure changes in insulin sensitivity, lipoprotein size, and postprandial lipemia after a 6-mo alteration in n-6:n-3.


METHODS
In a randomized, parallel design in 258 subjects aged 45-70 y, we compared 4 diets providing 6% of energy as PUFAs with an n-6:n-3 between 5:1 and 3:1 with a control diet that had an n-6:n-3 of 10:1. The diets were enriched in alpha-linolenic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), or both. Insulin sensitivity was assessed with the homeostatic model assessment of insulin resistance and the revised quantitative insulin sensitivity test.


RESULTS
Dietary intervention did not influence insulin sensitivity or postprandial lipase activities. Fasting and postprandial triacylglycerol concentrations were lower, and the proportion of sdLDLs decreased (by 12.7%; 95% CI: -22.9%, 2.4%), with an n-6:n-3 of approximately 3:1, which was achieved by the addition of long-chain n-3 PUFAs (EPA and DHA).


CONCLUSIONS
Decreasing the n-6:n-3 does not influence insulin sensitivity or lipase activities in older subjects. The reduction in plasma triacylglycerol after an increased intake of n-3 long-chain PUFAs results in favorable changes in LDL size.
Griffin
Margaret D
MD
School of Biomedical & Molecular Sciences, University of Surrey, Guildford, Surrey, United Kingdom.
Sanders
Thomas A B
TA
Davies
Ian G
IG
Morgan
Linda M
LM
Millward
D Joe
DJ
Lewis
Fiona
F
Slaughter
Suzanne
S
Cooper
Jackie A
JA
Miller
George J
GJ
Griffin
Bruce A
BA
D000368:Aged; D004042:Dietary Fats, Unsaturated / Q000008:administration & dosage* / Q000097:blood; D004281:Docosahexaenoic Acids / Q000008:administration & dosage / Q000097:blood; D015118:Eicosapentaenoic Acid / Q000008:administration & dosage / Q000097:blood; D015525:Fatty Acids, Omega-3 / Q000008:administration & dosage* / Q000097:blood; D043371:Fatty Acids, Omega-6 / Q000008:administration & dosage* / Q000097:blood; D005260:Female; D006801:Humans; D006949:Hyperlipidemias / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008049:Lipase / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000097:blood / Q000737:chemistry; D008077:Lipoproteins, LDL / Q000097:blood* / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D010316:Particle Size; D017698:Postmenopause; D019518:Postprandial Period; D014280:Triglycerides / Q000097:blood*; D017962:alpha-Linolenic Acid / Q000008:administration & dosage / Q000097:blood
D004042:Dietary Fats, Unsaturated; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D007328:Insulin; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D014280:Triglycerides; D017962:alpha-Linolenic Acid; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; D008049:Lipase