- omega-3 fatty acids attached to triglycerides, similar to those found in fish oil
- omega-3 fatty acids attached to phospholipids (alternatively referred to as marine lecithin),
- natural antioxidants, among them astaxanthin which is recognized as one of the most potent natural antioxidants in nature.
- 1 Krill species
- 2 Difference between krill oil and fish oil
- 3 Preclinical and clinical findings on krill oil vs. fish oil
- 4 Benefits of krill oil consumption
- 5 Krill biomass processing and krill oil manufacturing
- 6 Ecological concerns: sustainability of antarctic krill
- 7 Krill oil consumption as dietary supplement
- 8 References
- 9 Further reading
Krill are small crustaceans that can be found in all the world’s oceans, but mostly in the Northern (Arctic) and Southern (Antarctic) polar seas. They belong to the same animal family as shrimp, lobsters and crabs. There are more than 80 different known krill species. Among these, the Antarctic krill, called Euphausia superba, is the kind of krill that can be fished, because it lives in large swarms and swims in open water. Krill swim in huge swarms that can be stretch for several kilometers in length and have a density of up to one million individuals per cubic meter.
Difference between krill oil and fish oil
Krill oil is rich with omega-3 fatty acids, mainly Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA), bound mostly to phospholipids. Two papers have previously described the unique fatty acid composition of krill oil phospholipids. Krill oil is often compared with fish oil, since both are marine oils enriched with EPA and DHA. There are several differences between krill oil and fish oil, the main difference is the omega-3 fatty acids carrier. Unlike fish oil, in which the omega-3 FA are attached only to triglycerides, in krill oil the majority of omega-3 FA are attached to phospholipids while the rest are attached to triglycerides. Triglycerides consist of three fatty acids bound to a glycerol backbone, whereas phospholipids have only two fatty acids which are bound to a glycerol backbone. A phosphorus group, which is further linked to an organic, hydrophilic, headgroup, is also attached to the glycerol backbone of phospholipids. The headgroup can consist of choline (the major phospholipid in krill oil), ethanolamine, glycerol, inositol or serine. This difference in structure results in different chemical behavior: Triglycerides are highly hydrophobic, thus they do not mix with water. Conversely, phospholipids are amphipathic because they contain a hydrophilic headgroup on one end and hydrophobic chains on the other end. Due to this unique structure, phospholipids are able to mix with water. Another difference is the composition, krill oil contains the powerful natural antioxidant astaxanthin, which also gives krill oil its distinct deep red color. Although several studies have shown toxic residues in Antarctic krill and fish, other publication suggested that the lower an animal is on the food chain, it has a lower levels of toxins in its flesh. Preclinical and clinical studies with krill oil demonstrated its safety for human consumption, and krill oil was found to be Generally Recognized As Safe (GRAS) by the FDA, obtained authorization as a ‘Novel Food’ from the European Union and a ‘New Food Raw Material’ approval in China.
Preclinical and clinical findings on krill oil vs. fish oil
Studies showed that the bioavailability of fatty acids attached to phospholipids is better than fatty acids attached to triglycerides in general and specifically for omega-3 fatty acids. Thus, the absorbance of omega-3 FAs into target tissues, such as the heart, brain and the liver of tested animals is increased.
Researchers also tested omega-3 FA bioavailability in human intervention studies, demonstrating that the plasma levels of both EPA and DHA were significantly elevated following krill oil administration, leading to the conclusion that the omega-3 FAs in krill oil are highly bioavailable. In a randomized, double-blind, parallel clinical trial, 76 overweight and obese men and women received either krill oil, fish (menhaden) oil, or olive oil (the control) for one month. The daily amount of EPA was similar in the krill oil and fish oil group, but the DHA quantity was approximately half as much in the krill oil group compared to the fish oil group. After 4 weeks of supplementation the researchers found that the plasma EPA concentration was higher in the krill oil group compared to the fish oil group, and the average DHA concentration in the krill oil group was lower than in the fish oil group. Krill oil and fish oil supplementation both resulted in increased plasma EPA levels and increases in DHA, compared with the olive oil control group. In another study, 113 subjects with normal or slightly increased total blood cholesterol and/or triglyceride levels were randomized into three groups and given krill oil, fish oil, or no treatment for 7 weeks. The results from the krill and fish oil group showed higher EPA and DHA plasma levels than in the control group (who took no supplements at all) after seven weeks of administration but there were "no significant differences in the changes in any of the n-3 PUFAs between the fish oil and the krill oil groups". The krill oil group received 3 grams of krill oil daily and the fish oil group received 1.8 grams of fish oil daily, and the increases in EPA and DHA were similar in the krill oil and fish oil groups. Both studies demonstrated the increase in the levels of omega-3 FAs in plasma, a reflection of short term absorption. But neither was able to demonstrate accumulation of omega-3 FAs in media indicating long term absorption, such as in red blood cells (RBC).
A third study, this time with a cross over, randomized, double blinded design in healthy volunteers, tested the effect of consumption of KREAL krill oil compared to fish oil and placebo control (corn oil) on fatty acid profile in red blood cells (RBC) and plasma following 4 weeks of supplementation. This was the first study that tested the effect of omega-3 bound to PL consumption on the fatty acids profile in RBC, which reflects the tissue composition of long term absorption. In this study the dosages of n-3 PUFA for krill oil and fish oil treatments were similar. Results of this study demonstrated increased plasma and RBC EPA and DHA levels following treatment with both krill oil and fish oil compared to control. However, krill oil consumption significantly elevated plasma and RBC EPA levels compared to fish oil. Krill oil also significantly increased the level of total n-3 PUFA compared to fish oil. Results of this study indicate that krill oil is more effective than fish oil in increasing n-3 PUFA and reducing n-6:n-3 PUFA ratio in both plasma and RBC when the treatment groups receive the same levels of omega-3 fatty acids. In fact this study demonstrated that following consumption of krill oil levels of total omega-3 in RBC increased 2.7 times more than following consumption of triglyceride-based fish oil.
Benefits of krill oil consumption
Apart from being better absorbed, number of clinical studies revealed that krill oil is beneficial for human health in multiple indications. For example, beneficial effects on improving the symptoms of premenstrual syndrome (PMS) were demonstrated in two clinical trials (one against fish oil and one open-label as a component with other compounds) In these studies, krill oil was able to improve PMS symptoms of anxiety, mood, reduction in food craving and more. Another benefit for krill oil was demonstrated in amelioration of inflammation. Krill oil consumption led to a reduction in C-reactive protein (CRP) and subjects with cardiovascular disease and/or rheumatoid arthritis and/or osteoarthritis reported reduction in pain, stiffness and improved function. The most studied effects of krill oil are those related to various parameters associated with heart health and metabolic syndrome. Effect of blood triglyceride  and cholesterol reduction are associated with risk of heart disease. Reduction in blood glucose and HbA1C are both associated with reduced risk of diabetes. Additionally, a cognitive benefit of krill oil consumption, in elderly (61-73 years)subjects, was demonstrated.
Krill biomass processing and krill oil manufacturing
Immediately after harvesting, marine animals begin to deteriorate; once autolysis begins, bacteria present in the gut, skin or in water can easily enter tissues causing further deterioration and spoilage. Krill is more susceptible to spoilage and deterioration than other marine sources, therefore Krill biomass must be processed immediately after harvesting already aboard the fishing vessels, unlike fish processing which can be performed in land-based factories. In order to ensure the high quality of krill oil, the extraction process needs to be controlled. Different krill oil producers employ various methods of extraction and with different levels of expertise. Currently there are no standardized quality criteria for krill oil, and only a limited numbers of krill oil manufacturers present quality parameters in their quality assurance certificate of analysis. Thus, examination of krill oil from various manufacturers show dramatic differences in qualitative indication to the quality of the oils, such as odor, flowability, color, as well as in quantitative measures such as the levels of oxidation or volatile amine-derivatives. The omega-3 fatty acids and astaxanthin in krill oil are extremely sensitive to oxidation and degradation and therefore it is important to monitor the quality parameters in order to ensure product bio-effectiveness. There are several known parameters used to measure krill oil composition and quality: in terms of composition - levels of EPA/DHA, total phospholipids (%PL) and amount of astaxanthin; In terms of quality – peroxide value (indicative of oxidation) and degree of spoilage, as measure by trimethylamine (TMA) levels and total volatile basic nitrogen (TVN) levels.
Phospholipids and astaxanthin, naturally found in krill oil, are both thermo- and chemo- sensitive; thus, krill oil extraction and purification requires specialized knowledge of chemistry and process engineering in order to maintain appropriate purity, stability, and quality of the produced oil. This procedure is fundamentally different than that of other marine oils, such as fish oil, which are almost exclusively based on triglyceride (TG) purification. Triglyceride-based oils are normally manufactured using high temperature and aggressive chemical treatment, conditions that are not fit for phospholipid-based oils. Currently, worldwide, there are three primary manufacturers and suppliers for krill oil: (1) Neptune Technologies and Bioressources based in Laval, Quebec,Canada (2) Aker Biomarine Antarctic AS based out of Oslo, Norway and (3) Enzymotec Ltd., based in Migdal HaEmeq, Israel.
Ecological concerns: sustainability of antarctic krill
Antarctic Krill is a keystone species of the Antarctic ecosystem and provides an important food source for marine life in the Southern Ocean (i.e whales, seals, fish, squid and birds). Since the beginning of krill harvesting, many eco-friendly people and organizations expressed concerns regarding its sustainability however, krill fishery and harvesting are rigorously regulated and monitored by the Commission for the Conservation of Antarctic Marine Living Resources. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is an international treaty between 25 nations that seeks to manage Antarctic fisheries with the goal of preserving species diversity and stability of the entire Antarctic marine ecosystem. CCAMLR was established in 1982 in response to un-regulated harvesting of seal and other marine life in that area which led to over-exploitation of their population. Today fishing of Antarctic krill is tightly regulated in order to ensure the sustainability of the species. The fishing is regulated by limiting certain subzones of the Southern Ocean, close monitoring of fishing vessels, control of the depth for krill harvesting, and by setting limits for the amount of krill that can be harvested per year. CCAMLR has successfully implemented a precautionary and ecosystem approach in managing the krill fishery. The krill fishery is considered to be among the best managed fisheries in the world, providing strict catch limits on licensed vessels, and scientific observers on board. CCAMLR scientists are working to take into account the possible effects of climate change on the ecosystem as well as effects of changes in technology and operational pattern of krill fishing vessels on the fishery when making management decisions.
Krill oil consumption as dietary supplement
Many of the claims regarding consumption of krill oil suggest it is more bioavailable than fish oil, although krill oil is lower in EPA and DHA than fish oil. The commonly used dosages for krill oil are 500 mg to 1g per day (corresponding to 1-2 capsules). For nutritional treatment of some diseases, higher dosages are recommended. One gram of krill oil is commonly composed of 40% phospholipids, 100 mg EPA and 55 mg DHA, and 100-300 mcg of Astaxanthin. It has recently published that a 2nd generation krill oil is now available containing 40% phospholipids, 210 mg EPA, 140 mg DHA and 200-1500mgr Astaxanthin. Fish oil pills, by comparison, can contain up to 1000mg of EPA and DHA and a 90 gram tin of mackerel fillets contains around 4000mg of omega 3 fatty acids.
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