Omega-3 fatty acids from Superba Krill Oil show increased bioavailability compared with triglyceride omega-3s.
Dietary supplementation with the long-chain omega-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has gained significant interest as a result of several associated health-promoting benefits. Not only were both EPA and DHA shown to be essential in early retinal and brain development, but were also identified as promoting cognitive and immune system functions and linked to the prevention of cancer and cardiovascular diseases. The human body is limited in its ability to produce EPA and DHA; the intake of these fatty acids must therefore be augmented through the diet. Although omega-3 fatty acids may be obtained through the consumption of seafood, dietary supplements are a reliable alternative or addition.
Krill: An Abundant and Sustainable Source of Nutrition
One rather novel source of omega-3 PUFAs is krill oil extracted from Euphausia superba, an Antarctic krill species. Krill are shrimp-like invertebrates that live in huge swarms and feed on microscopic algae. These algae are able to produce omega-3 fatty acids, which accumulate in the eggs and body of krill and may consequently be extracted in krill oil. Moreover, algae are capable of synthesizing the powerful antioxidant, astaxanthin, a carotenoid that is subsequently taken up by krill and protects the PUFAs from oxidation. It is also the reason for the characteristic red colour of krill oil. The krill's place at the bottom of the food chain and its clean habitat prevent the accumulation of contaminants that are often found in marine life higher in the food chain. Krill is one of the most abundant species on Earth with a biomass of approximately 500 million tonnes. Krill harvesting is restricted to 4 million tonnes by the Commission for the Conservation of Antarctic Marine Living (CCAMLR) to ensure sustainability and prevent a damaging impact on the availability of krill for whales, birds, seals or any other species from occurring. The current annual catch of 200,000 tonnes per year from all krill fisheries is far below this margin.
Krill Oil: Rich in Omega-3 Phospholipids
Most importantly, the majority of the omega-3 fatty acids EPA and DHA found in krill oil are bound to phospholipids, whereas other marine oils confine these to triglyceride or ethyl ester forms; the proportion of phospholipids in krill oil is approximately 40%. There are several different types of phospholipids and EPA and DHA are particularly rich in phosphatidylcholines (PC). A study describing the contents of Superba krill oil has found EPA and DHA to be present in most of the 69 identified choline-containing phospholipid classes. 1 In PC, two fatty acid chains are attached to a glycerol group that is connected to choline over a phosphate group (Figure 1A); this structure enables the formation of phospholipid bilayers, which are essential for the structure of cell membranes in all life on Earth. Dietary phospholipid carriers might facilitate the transportation of omega-3 fatty acids through the body and its subsequent integration into cell membranes. As an integral part of cell membranes, EPA and DHA have the ability to influence membrane fluidity, the associated signalling processes and other metabolic parameters in the cell.
By contrast, in the triglyceride form, three fatty acid chains are attached to a glycerol group (Figure 1B). Dietary triglycerides have physiological functions in the body that differ from those of phospholipids, being used principally as an energy source or to store energy in fat tissues. In addition, there is a difference in the digestion and absorption of phospholipids and triglycerides in the small intestine. Omega-3 fatty acids and lyso-PC can be absorbed in the gastrointestinal system following the digestion of phospholipids by enzymes called lipases. Omega-3s in triglycerides are insoluble in water and their absorption depends on bile salts and enzymes in the small intestine. The solubility of krill oil phospholipids in water has the advantage of decreasing the digestive discomfort sometimes seen with omega-3s provided in triglyceride form.
Increased Bioavailability of EPA and DHA
Studies have demonstrated that increased EPA/DHA blood levels are associated with health-promoting benefits in humans; the bioavailability of these omega-3 fatty acids in the blood is therefore of great importance. ?Bioavailability' accounts for the quantity of a substance that reaches the blood and describes the absorption and survival rate of the substance in the body. Two recent human intervention studies investigated whether the molecular form (phospholipid versus triglyceride) of omega-3 fatty acids is of importance for the bioavailability of EPA and DHA in blood plasma. 2,3 The study, performed by Kevin C. Maki and coworkers at the Provident Clinical Research and the Meridien Research Centers, was set up as a randomized, double-blind, parallel arm trial. Within this setup, 76 overweight and obese men and women were randomly distributed into three groups to take Superba krill oil, fish oil or olive oil for 4 weeks. To avoid any influence, the supplementation administered was unknown to both the study subjects and the researchers. Although the received daily amount of EPA was similar in the krill oil and fish oil group, the DHA quantity was approximately half as much in the krill oil group compared with the fish oil group. Nevertheless, at the end of the study period, plasma analysis showed that the mean EPA concentrations were higher in the krill oil group compared with the fish oil group. The mean DHA concentrations were similar in both groups. Both sources of omega-3 fatty acids were safe, generally well tolerated and significantly increased plasma EPA and DHA levels compared with the control group. Most importantly, krill oil supplementation (2 g/d) resulted in increased plasma EPA bioavailability and resulted in equal bioavailability in the case of DHA, but at half the dosage when compared with fish oil. 2 Overall, after dose adjustment, it was seen that the total increase of EPA and DHA in the plasma of the subjects who received Superba krill oil for 4 weeks was 24% higher than the subjects who received fish oil (Figure 2).
The second study, undertaken by researchers at Akershus University College and University of Oslo, Norway, investigated whether a lower dose of EPA and DHA provided in phospholipids, compared with omega-3 fatty acids provided in triglycerides, showed equal bioavailability of these fatty acids in plasma. In this study, 113 subjects with normal or slightly increased total blood cholesterol and/or triglyceride levels were randomized into three groups and given Superba krill oil, fish oil or a placebo for 7 weeks. The daily supplementation of total EPA and DHA was approximately 37% less in the krill oil group than in the fish oil group. The results showed that dietary omega-3 administration led to a similar increase in plasma omega-3 fatty acids in both the krill and fish oil groups compared with the control group. These findings suggest that a lower dosage of EPA and DHA in phospholipid form is required to obtain plasma EPA and DHA levels comparable with the triglyceride form of omega-3 supplementation.
After adjusting the EPA and DHA levels to the daily dose given, the results from the krill oil group suggest an impressive 45% higher total EPA and DHA plasma level than that present in the fish oil group after 7 weeks of administration (Figure 2). Moreover, the subjects with the highest baseline values of triglycerides further benefited from krill oil supplementation and showed decreased plasma triglyceride levels. Additionally the HDL-cholesterol/triglyceride ratio, a risk predictor for heart disease, was significantly decreased after Superba krill oil administration, but not after fish oil treatment. These two human clinical studies demonstrate that the intake of Superba krill oil is more potent than fish oil in increasing total plasma EPA and DHA values. Their results suggest that there is a higher bioavailability of omega-3 fatty acids bound to phospholipids than in the triglyceride-bound omega-3s found in fish oil. Thus, if managed carefully, krill can be a rich and sustainable source of omega-3 fatty acids that are important for human health.
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For more information
Henrik Traaholt
Business Director and Brand Manager
Aker Biomarine Antarctic AS
Tel. +47 2413 0122
henrik.traaholt@akerbiomarine.com
www.akerbiomarine.com
[Reference]
References
1. B. Winther, et al., 'Elucidation of Phosphatidylcholine Composition in Krill Oil Extracted from Euphausia superba,' Lipids 46 (1), 25-36 (2010).
2. K.C. Maki, et al., 'Krill Oil Supplementation Increases Plasma Concentrations of Eicosapentaenoic and Docosahexaenoic Acids in Overweight and Obese Men and Women,' Nutr. Res. 29 (9), 609-615 (2009).
3. S.M. Ulven, et al., 'Metabolic Effects of Krill Oil are Essentially Similar to Those of Fish Oil but at Lower Dose of EPA and DHA, in Healthy Volunteers,' Lipids 46 (1), 37-46 (2011).
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