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Krill Oil: Bioavailable Source of Omega-3s

By Gene Bruno, MS, MHS
It seems that hardly a week or two passes without some new study being reported about the importance of the omega-3 fatty acids eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) to human health. Unfortunately, our Western diets are deficient in omega-3 fatty acids, and have excessive amounts of omega-6 fatty acids compared with the diet on which human beings evolved and their genetic patterns were established.1 The ultimate ramifications of this were reported in a landmark study from the Harvard School of Public Health, which indicated that omega-3 fatty acid deficiency has significant health implications annually in the U.S., and optimal health depends on achieving appropriate dietary levels of omega-3s. This is a prime way of enhancing health by simply improving dietary choices,2 making a strong case for supplementation with omega-3 fatty acids.
At this point, the real question is not should we supplement with omega-3 fatty acids, but rather what source should we supplement with? Fish oils are the most common dietary supplement form of omega-3 fatty acids, but a lesser-known alternative called krill oil also has a number of excellent health benefits.

Krill Oil: Composition and Mechanism of Action
Krill are a shrimp-like crustacean, most of which are only about 1-2 centimeters long and serve as food for certain types of whales and seals, as well as manta rays, whale sharks and a few seabird species. There are an enormous number of krill in our oceans. In fact, one species of krill, the Antarctic krill, makes up an estimated biomass of over 500 million tons, roughly twice that of humans.
Krill oil, derived from krill, contains significant amounts of the omega-3 fatty acids EPA and DHA. Although the concentration of omega-3 fatty acids in krill oil is usually less than in fish oil products, krill oil contains other valuable constituents including phospholipids—primarily consisting of phosphatidylcholine, with lesser amounts of phosphatidylethanolamine and lysophosphatidylcholine.3 Krill oil also provides vitamin A, vitamin E (alpha-tocopherol) and astaxanthin, a powerful carotenoid antioxidant.4-5 It is this unique composition, rather than just the omega-3 fatty acid content, that seem to provide krill oil’s spectrum of benefits. Krill oil’s mechanism of action involves anti-inflammatory and blood viscosity balancing properties, as well as promoting healthy levels of C-reactive protein.6 In addition, animal research has shown that krill oil seems to increase hepatic antioxidant enzymes such as catalase, glutathione peroxidase and superoxide dismutase (SOD) while reducing hepatic arachidonic acid,7 which is used for the formation of pro-inflammatory prostaglandins.

Krill Oil vs. Fish Oil
One study investigated the effects of krill oil and fish oil on a number of parameters in one hundred thirteen subjects to determine if there were differences in the effects of these two sources of omega-3 fatty acids, and to see if they had a different influence on the plasma level of EPA and DHA.8 The subjects were randomized into three groups and given either six capsules of krill oil (n = 36; 3.0 g/day, EPA + DHA = 543 mg) or three capsules of fish oil (n = 40; 1.8 g/day, EPA + DHA = 864 mg) daily for 7 weeks. A third group did not receive any supplementation and served as controls (n = 37). The results were a significant increase in plasma EPA and DHA in subjects supplemented with krill oil or fish oil as compared with the controls—but there were no significant differences in changes of EPA and DHA levels between the fish oil and the krill oil groups even though the EPA + DHA dose in the krill oil was 62.8 percent of that in the fish oil. Likewise, changes in serum lipids and markers of oxidative stress and inflammation were not significantly different between the fish oil and the krill oil groups. This study is particularly noteworthy since it demonstrated similar benefits between fish oil and the krill oil, but with lower levels of EPA + DHA dose in krill oil.

Improvements in Metabolic Parameters
In an animal study, the effects of krill oil on cardiometabolic health factors in mice fed a high-fat diet were examined.10 The results were that krill oil supplementation caused a significant reduction in liver weight and total liver fat, by promoting a healthy balance of liver triglycerides and cholesterol. Krill oil also promoted a healthy serum cholesterol and blood glucose metabolism. Serum adiponectin was increased in mice fed krill oil, which is significant since adiponectin is a fat-burning hormone, suggesting a possible reduction in fat stores. According to the researchers, these results suggest that krill oil may be of therapeutic value in promoting healthy metabolic parameters and supporting liver efficiency through an increase in liver fat metabolism.
Of greater significance is similar research conducted in human subjects, in which overweight human subjects with elevated levels of endocannabinoids received 2 grams /daily of either krill oil or menhaden oil, which provides 309 mg of EPA/DHA 2:1 and 390 mg/d of EPA/DHA 1:1, respectively, or olive oil for four weeks.19 The results were that krill oil only was able to significantly decrease 2-arachidonoylglycerol, which was directly correlated to fatty acid ratio found in the krill oil. These data show for the first time in humans that relatively low doses of omega-3 fatty acids found in krill oil significantly decrease plasma 2-arachidonoylglycerol levels in overweight subjects.

Cardiovascular and Colon Health
Cardiovascular health and the healthy division and differentiation of colon cells are known to be closely related to dietary factors. This study evaluated the effects of krill oil 1) on serum lipids in rats and 2) human colon cells.20 Serum lipids of rats fed with a high-fat diet (HFD) and different doses of krill oil were analyzed. The results were that body weights decreased significantly. In addition, krill oil promoted healthy levels of: 1) Total cholesterol 2) LDL cholesterol in all dose groups and 3) triglycerides in low and mid dose groups. Furthermore, compared with the control group, exposure of colon cells to krill oil resulted in healthy cellular division and differentiation.

Krill Oil Safety
Krill oil appears to be well tolerated, with no indication of adverse effects on safety parameters.21 Theoretically, some people who are allergic to seafood might also be allergic to krill oil supplements. (Note: Since krill oil contains the same fatty acids found in fish oil, it might also inhibit platelet aggregation. Therefore, taking high doses of krill oil with antiplatelet or anticoagulant drugs might, theoretically, increase the risk of bleeding.)22

Krill oil’s unique composition, favorable performance compared to fish oils, its effects on metabolic parameters, benefits for cardiovascular and colon health and its safety profile all make a compelling case for this dietary supplement to provide a needed daily source of omega-3 fatty acids. The phospholipid-bound omega-3s from krill are highly bioavailable, which facilitates their absorption and incorporation into cells of the body.

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This article was published on Tuesday April 12, 2011.
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