Increased Omega-3s a Mixed Bag on Insulin Sensitivity

LONDON—A new British study reports altering the dietary ratio of omega-6 (n-6) to omega-3 (n-3) fatty acids by increasing intake of n-3s failed to improve insulin sensitivity scores or postprandial lipemia (high blood lipid count), but did reduce low-density lipoprotein (LDL) size. The study was reported in the December issue of American Journal of Clinical Nutrition (84,6:1290-98).

Scientists from several London-area universities jointly investigated insulin sensitivity, lipoprotein size, and postprandial lipemia after a six-month alteration of the n-6 to n-3 ratio in 258 subjects aged 45 to 70. Researchers compared three diets—each providing 6 percent of energy as polyunsaturated fatty acids (PUFAs)—with an n-6 to n-3 ratio between 5-to-1 and 3-to-1 and a control diet with an n-6 to n-3 ratio of 10-to-1. The omega-3s in the study were either alpha-linolenic acid (ALA), a combination of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), or both. Insulin sensitivity was assessed using the homeostatic model assessment (HOMA), which quantifies insulin resistance and beta cell function, along with the revised quantitative insulin sensitivity test.

Results showed the omega-3 dietary intervention did not influence insulin sensitivity or postprandial lipase activities. However, fasting and postprandial triacylglycerol concentrations were lower in the omega-3-enriched groups, which also showed significantly decreased proportions of small, dense LDLs, at an n-6 to n-3 ratio of around 3-to-1.

Researchers concluded decreasing the n-6 to n-3 ratio does not influence insulin sensitivity or lipase activities in older subjects; however, the reduction in plasma triacylglycerol following an increased intake of omega-3s results in favorable changes to LDL size.

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