Fish Oil Supplementation for Insulin Resistance: Nothing but a Fish Burp?

Introduction

Omega-3 fatty acids from fish oil, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are kinds of polyunsaturated fatty acids (PUFAs) thought to have^[1] anti-inflammatory properties. Their effects may come about in part due to restructuring of the cell membrane^[2]. This restructuring, in turn, can possibly result in healthful downstream effects as shown in Figure 1. Examples include influencing autoimmune diseases^[3] and fatty liver^[4], promoting healthy pregnancy^[5], and preventing cardiovascular disease. In cardiovascular disease, the impact of omega-3 fatty acids is largely thought to be related to lowering triglyceride levels^[6].

While a large amount of research has been done on the effects of fish oil for cardiovascular disease^[7], scientists are also interested them for their potential in treating other inflammatory conditions, in particular insulin resistance. Insulin resistance is an important issue in public health due to its increasing prevalence^[8] among nondiabetic adults and because it often precedes the development of metabolic diseases like type 2 diabetes, which, once present, increases the risk for other diseases, including cancers^[9]. Since insulin resistance is thought to have an inflammatory component^[10], and fish oil may be anti-inflammatory^[11], it is reasonable to think that fish oil could impact insulin resistance.

Evidence on this topic exists. The study under review is a meta-analysis which updates an earlier one^[12] published in 2011. The 2011 study pooled the outcomes of 11 randomized controlled trials (RCTs) testing the effects of fish oil supplementation on insulin sensitivity. Overall, this earlier study found no effects of fish oil on insulin sensitivity. In the years following this original meta-analysis, more research was done; the authors of the present study attempted to capture emerging evidence.

Incidence of insulin resistance rising and is known to increase the risk for type 2 diabetes. Since inflammation is thought to play a role in both insulin resistance and type 2 diabetes, it’s plausible that anti-inflammatory fats, such as omega-3s, may slow down or even reverse insulin resistance. The study under review examines the existing evidence for the impact of fish oil, specifically EPA and DHA, on insulin resistance. The current study is an update of a 2011 meta-analysis and systematic review examining the same effects.

Who and what was studied?

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