Journal Name:
Am. J. Clin. Nutr.
Article Title:
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
Date Written:
2006
Volume:
84
Number:
0
Page:
1290
Author(s):
Griffin, M.D.; Sanders, T.A.B.; Davies, I.G.; Morgan, L.M.; Millwar, D.J.; Lewis, F.; Slaughter, S.; Cooper, J.A.; Miller, G.J.; Griffin, B.A.
Article:
Insulin resistance and elevated fasting and postprandial blood insulin concentrations are associated with an increased risk of ischemic heart disease (IHD). The prevalence of insulin resistance increases with age, obesity, and low physical activity and has reached epidemic proportions in most developing countries. Part of the increased risk of IHD associated with insulin resistance and hyperinsulinemia appears to be associated with dyslipidemia, commonly referred to as the atherogenic lipoprotein phenotype, which is characterized by elevated VLDL concentrations, impaired postprandial clearance of triacylglycerolrich lipoproteins, low HDL-cholesterol concentrations, and a preponderance of small, dense LDL particles.
Modifying the intake of polyunsaturated fatty acids (PUFAs) may correct some of these lipid abnormalities by increasing the sensitivity of tissues to insulin. N-6 and n-3 fatty acids appear to have different effects on lipid metabolism, particularly with regard to plasma triacylglycerol, LDL, HDL, and lipoprotein subclasses. Evidence from prospective cohort studies and secondary prevention trials of IHD suggest that altering the dietary ratio of n- to n-3 fatty acids (n-6:n-3) decreases the risk of fatal IHD.
The Quantification of the Optimal n-6/n-3 ratio in the UK Diet (OPTILIP) Study was designed to assess the effects of lowering the dietary n-6:n-3 on cardiovascular disease risk factors in older persons. In particular, the objective was achieved by using a food-based intervention that involved increasing the relative intake of alpha-linolenic acid (ALA) or n-3 long chain PUFAs (notably EPA and DHA), or both, in relation to the intake of n-6 linoleic acid. Parameters of interest included insulin sensitivity, postprandial lipid metabolism, and lipoprotein size.
The rationale for selecting an older population of men and women was because of their substantial risk of cardiovascular events. Most of the subjects (89%) had one or more of the established risk factors for IHD [serum cholesterol >5.0 mmol/L, blood pressure >140 (systolic)/90 (diastolic), cigarette smoking], and 60% of the subjects had impaired fasting glucose.
It was found that decreasing the n-6:n-3 did not influence insulin sensitivity or lipase activities in older subjects. A reduction in plasma triacylglycerol was noted with an increased intake of n-3 long-chain PUFAs and resulted in favorable changes in LDL size.
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