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n-3 long-chain polyunsaturated fatty acids in type 2 diabetes: A review

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Abstract

Historically, epidemiologic studies have reported a lower prevalence of impaired glucose tolerance and type 2 diabetes in populations consuming large amounts of the n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) found mainly in fish. Controlled clinical studies have shown that consumption of n-3 LC-PUFAs has cardioprotective effects in persons with type 2 diabetes without adverse effects on glucose control and insulin activity. Benefits include lower risk of primary cardiac arrest; reduced cardiovascular mortality, particularly sudden cardiac death; reduced triglyceride levels; increased high-density lipoprotein levels; improved endothelial function; reduced platelet aggregability; and lower blood pressure. These favorable effects outweigh the modest increase in low-density lipoprotein levels that may result from increased n-3 LC-PUFA intake. Preliminary evidence suggests increased consumption of n-3 LC-PUFAs with reduced intake of saturated fat may reduce the risk of conversion from impaired glucose tolerance to type 2 diabetes in overweight persons. Reported improvements in hemostasis, slower progression of artery narrowing, albuminuria, subclinical inflammation, oxidative stress, and obesity require additional confirmation. Expected health benefits and public health implications of consuming 1 to 2 g/day n-3 LC-PUFA as part of lifestyle modification in insulin resistance and type 2 diabetes are discussed.

Section snippets

Epidemiologic studies

More than 30 years ago disease patterns among the Greenland Inuit, Alaskan natives, and other Arctic and subarctic natives showed far lower incidence of type 2 diabetes than in Danes, US residents, or others (26, 27, 28, 29). Type 2 diabetes was less prevalent among Japanese islanders compared to their mainland counterparts (30). Lower prevalence of type 2 diabetes was attributed mainly to diets rich in n-3 LC-PUFAs. During the past 15 years, the incidence of type 2 diabetes has increased

Glucose control

In a review, Nettleton (44) noted that several clinical studies in the 1980s and early 1990s reported adverse effects on blood glucose control and insulin activity in subjects with type 2 diabetes who consumed large amounts of fish oil (45, 46). It is now believed that these deleterious effects were largely attributable to the high doses used, like 10 g fish oil per day or more. Recent studies using low doses of n-3 LC-PUFAs, ranging from 1 to 2 g/day, have reported no deterioration in glucose

Implications

Promising results from studies of patients with insulin resistance and type 2 diabetes indicate that consumption of n-3 LC-PUFAs improves lipid profiles, may retard disease progression, modestly reduces blood pressure, and may deter the onset of more serious cardiovascular complications, including mortality. However, proof that n-3 LC-PUFAs can prevent subjects with insulin resistance or impaired glucose tolerance from developing type 2 diabetes remains to be established. Effects of n-3

J. A. Nettleton is principal, ScienceVoice Consulting, Denver, CO.

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  • Cited by (0)

    J. A. Nettleton is principal, ScienceVoice Consulting, Denver, CO.

    R. Katz is president, Omega-3 Research Institute, Inc, Bethesda, MD.

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