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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).
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?
What were the findings?
What does the study really tell us?
The big picture
Frequently Asked Questions
What should I know?
Other Articles in Issue #10 (August 2015)
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Put down the apple and have some chedda
Although both cheese and meat are lumped into the “watch out!” category in hearthealth recommendations, dairy products often show neutral or positive associations with cardiovascular health. But how do cheese-rich diets fare in randomized trials when compared to other diets? This trial tested three diets against each other in a highly controlled fashion: a cheese diet, meat diet, and high-carb diet.
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Omega-3: kid-tested, mom approved?
While heart health gets much of the attention for fish oil benefits (which, incidentally, are often overstated), outcomes in children typically show more promise. This study, involving children and their parents living on the island of Mauritius, explored possible behavioral benefits to fish oil supplementation. And not just the childrens’ behavior, but the parents’ as well!
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Priming the pump: carb levels for endurance exercise
If you run, cycle, or do anything long and sweaty, then you already know that carb intake is especially important for endurance activity. But recommended intakes range from around 30-60 grams, which is pretty broad. This trial can help you get to a more specific number, and possibly perform better.
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A thorough trial of carb intake for diabetes
There are few conditions where carbs play as direct of a role as in type 2 diabetes. Yet the recommended carb intake levels for this condition aren’t so different than for the general population. That may change at some point, due to trials like this one, which is more highly controlled and thorough than previous lower-carb & diabetes studies.
- Interview: Elke Nelson PhD
- Interview: Marguerite McDonald, MD
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“B” is for breakouts
B vitamins are commonly thought of as harmless, due to being water-soluble. As nutrition junkies know, that view lacks nuance, and B vitamins can indeed be harmful in certain situations. As an example, this elegant series of experiments sheds new light on the mechanism by which vitamin B12 may impact acne formation.
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Wellness, Not Weight
By Cristen Harris, PhD
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Salt in the wound
Science and mystery often go hand in hand, and this is a perfect example: when you have a skin infection, you tend to have more salt in the infected skin. But why is that? Well, where there’s smoke, there’s fire. The salt is probably doing something in regards to immune response, and it’s possible that how much salt you eat could also play a role. Resist the urge to skip to the end of this mystery -- the buildup is worth it.
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Carbs-protein or protein-carbs …
Does food order matter? Grandma always said “You have to eat your vegetables first if you want dessert!”. If you substitute “carbs” in for dessert, grandma might have hit another one out of the park. It’s possible that simply switching the order of what you eat might benefit blood sugar control, which would be a relatively easy way to address the thorny public health issue of type 2 diabetes
