All up in your krill: The story on krill

Oil thus far has been fairly simplistic: it’s better than fish oil and more expensive. But there’s a reason why you can’t draw conclusions based off few studies, and successful results in one condition don’t apply to other conditions. This trial gives some of the first pieces of evidence for possible negative metabolic effects of krill oil.

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Study under review: Supplementation with a blend of krill and salmon oil is associated with increased metabolic risk in overweight men

Introduction

Fish oil. By now, most of our readers have heard of it. Fish oil has been tested as a potential cure for just about everything under the sun. From treating epilepsy^[1] (covered in NERD issue #1), to preventing cognitive decline in the elderly, to reducing fatigue^[2]. The Examine.com page on fish oil currently has more than 700 citations and over 90 categories in the Human Effect Matrix, which covers each of the known effects of a supplement.

However, not as many people know about krill oil: fish oil’s lesser known cousin. Both contain the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are the primary catalysts for many of fish oil’s benefits. However, krill oil has a distinct advantage in that it may be better absorbed than fish oil. One trial has suggested that the EPA in krill oil may be taken up^[3] better depending on the type of oil. A preliminary trial has even indicated that krill oil could potentially be superior at improving cholesterol profiles^[4] over fish oil. Krill oil also contains astaxanthin, a potent antioxidant that gives salmon and krill their reddish pigmentation. Figure 1 shows a selection of health effects that astaxanthin has been researched for (albeit not combined with krill oil, and at varying doses).

Figure 1: Some human effects (or lack thereof) of astaxanthin

And yet, research into krill oil is not terribly extensive. The study under review helps expand krill oil’s evidence base by examining its use as a means to improve insulin sensitivity. Insulin sensitivity refers to how much insulin the body needs to produce in order to manage blood sugar levels. Being insulin-sensitive is a sign of metabolic health, while insulin resistance can be a warning sign of metabolic dysfunction. People with insulin resistance would need their body to pump out a lot of insulin to bring blood glucose down to a normal level. Before the publication of this study, no human trials had investigated the outcomes of krill oil supplementation on insulin sensitivity. Previous research had found omega-3 fatty acids to exert little positive or negative change on insulin sensitivity^[5], but these studies used a number of different omega-3 sources, varying doses, assorted control oils, and had confounding variables, like restricting participant calories in addition to administering an omega-3 supplement. Complexities like these make it hard to determine the true relationship between insulin sensitivity and omega-3s.

Although the sum of evidence to date shows little change in insulin sensitivity after omega-3 supplementation, there are many confounding variables that make it hard to say if omega-3s have an effect or not. Krill oil may possess some unique properties that could give it an advantage over fish oil, since it is easily absorbed and contains astaxanthin, an antioxidant.

Who and what was studied?

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