Phospholipids offer certain advantages over triglycerides in terms of stability, organoleptic properties, uptake and tissue deposition of fatty acids, based on their different structure and physicochemical properties. Phospholipids in krill oil are identical to human cell membrane phospholipids. Furthermore, triglycerides are more readily solubilized and absorbed when accompanied by phospholipids.

 
a. Phospholipids

Phospholipids are chemically distinct from fats and other lipids by containing phosphorous and having their own characteristic molecular structure. Phospholipids contain a glycerol moiety substituted with one or two acyl/alkyl chains (or a ceramide chain) (Silvius 1993).

They are capable of simultaneously mixing in both water and oil and are able to spontaneously self-assemble into liposomes much like cell membranes. Phospholipid fatty acids are key structural components of human cells and cell organelles and play a vital role in membrane functioning (Batetta 2009, Kidd 2007A). Systemic transport pathways (e.g., lipoprotein particles in blood) and especially transport across cell membrane and sub-cellular membranes involve phospholipids. Transporting, packaging and utilizing fat in various tissues depends on phospholipids (Bernoud 1999, Cevc 1993, Kidd 2007A). Thus, functioning of the body's cells, tissues and organs is affected by the bioavailability of various phospholipid fatty acids (Kidd 2007A). The body can synthesize phospholipids from other substances but usually a lot of metabolic energy is required.

In addition to their physicochemical characteristics, membrane phospholipids are used to liberate specific fatty acids for crucial regulatory events. Eicosanoid formation is dependent on utilizing certain polyunsaturated fatty acids attached to the middle carbon of the glycerol backbone of phospholipids. Thus, phospholipids determine biological activity of many cellular and bodily functions. Phospholipids are also seen as conditionally essential nutrients for some human populations.

There are two phospholipid classes: one which contains a glycerol backbone and the second which contains a sphingosine backbone (Hanahan 1997). Some of the more common phosphoglycerides are phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), glycerophosphocholine (GPC), and omega-3 phospholipids (OPL) (SI 2007). All of these are used in dietary supplements.

Phosphatidylcholine, also called lecithin, is the most abundant phospholipid in mammalian cells and is about 50%-60% of the total lipids in cells or membranes (Hanahan 1997A, Kidd 2007A, Yorek 1993). It only has a sn-3 stereochemical configuration and is considered a strong zwitterion over the entire pH range. The acyl (fatty acid) groups attached to C-1 and C-2, by an ether bond, are usually long chain (13-21) hydrocarbon residues (Hanahan 1997A, Silvius 1993). The phosphate group and choline groups are attached on C-3. Hydrocarbon chains attached to C-1 are usually highly saturated whereas the acyl residues attached to C-2 are 95% unsaturated (Hanahan 1997A). Phosphatidylcholine belongs to a class II lipid, which are lipids that are insoluble (very low critical micelle concentration) but swell in water to form ordered liquid crystalline or mesomorphic phases (McIntosh 1993). This is important because of transport mechanisms across the cell membrane of vital metabolites that are dependent on various electrical charges (Cevc 1993).

Figure 1.

Phosphatidylcholine Structure. R₁ and R₂ are long-chain fatty acids.

Phosphatidylethanolamine is the second most abundant phospholipid at around 22-29% of total phospholipids in cells (Hanahan 2007B, Yorek 1993). PE is similar in structure to phosphatidylcholine but has an ethanolamine group attached to the phosphate group instead of a choline group. PE can be found in cell membranes in three different chemical forms. PE is a zwitterion over the pH range of 2-7 and in the pH range 7-10 it is in the anionic form. Due to its more polar head group PE causes a more fluid lipid membrane and the fatty acids attached usually have a higher degree of unsaturation as compared to PC. Phosphatidylethanolamine is involved in the formation of diacylglycerol as a second messenger. This mechanism appears to play a role in the transformation and differentiation of cells (McNulty 1991, Lang 1995, Momchilova 1999). Another area of phosphatidylethanolamine involvement is in ATP generation by cellular mitochondria and these PE are derived from phosphatidylserine (Kidd 2007A).

Figure 2.

Phosphatidylethanolamine Structure. R₁ and R₂ are long-chain fatty acids.

Phosphatidylserine is another important phospholipid. It is also called an "acidic phospholipid" because of the acidic nature of the substituent attached to the phosphoric acid residue (Hanahan 1997B). Thus, its ionic character separates PS from phosphatidylcholine. Phosphatidylserine occurs naturally throughout the body in all cells and is about 12-19% of total phospholipids in cells. PS is the only amino acid-containing phosphoglyceride found in mammalian cells and only exists in the diacyl form (Hanahan 1997B). In the cell membrane bilayer PS is most often located in the inner membrane enwrapping key membrane proteins (Kidd 2007A). Phosphatidylserine is a key component of protein kinase C enzyme activity. It is also involved in the blood coagulation process via prothrombin formation (Hanahan 1997B). Nerve cells contain the most PS and thus PS has a significant presence in the brain (Kidd 2007A).

Figure 3.

Phosphatidylserine Structure. R₁ and R₂ are long-chain fatty acids.

Phosphatidylinositols are present in the lowest concentrations in cell membranes of the four major phospholipids. The presence of inositol in the phosphate head group allows for additional phosphate groups to be added to the inositol portion, making the PI family more complex than merely its fatty acid content. At least seven different phosphorylated PIs, called phosphoinositides, occur in mammalian cell membranes. PI is intimately involved in cell signaling, lipid trafficking, cell communications and receptor activation events (Fruman 1998; Hanahan 1997B; Hokin 1985; Martin, 1998; Nishizuka 1985; Pochynyuk 2006; Vicinanza 2008). A polyunsaturated fatty acid, usually arachidonic acid, is common on the second carbon of the glycerol backbone. The molecular complexity of PI allows for extensive control of signaling events on cell membranes, and an entire system to utilize this complexity exists in cells.

Figure 4.

Phosphatidylinositol Structure. R₁ and R₂ are long-chain fatty acids.

Glycerophosphocholine (GPC) is yet another form of phospholipid needed in the human body. It is unique by being present in the water phase (cytoplasm) of cells. GPC is a major metabolic precursor to phosphatidylcholine (Kidd 2007B, SI 2007). Since it is water-soluble and stable in the cytoplasm, GPC is an important phospholipid reservoir for all organs (SI 2007).

Krill Omega-3 phospholipids are mostly phosphatidylcholine/ethanolamine with DHA and EPA fatty acids attached to the middle carbon of the glycerol backbone (sn2 nomeclature). Antarctic krill phospholipids, such as E. superba, typically have more than 40% phospholipids by weight and around 30% EPA and DHA (SI 2007). Most of the omega-3 fatty acid content in krill oil is incorporated structurally within phospholipids and thus cell membranes.

Marine omega-3 fatty acids in dietary supplements are usually derived from fish, such as fish body oil and cod liver oil, or algal oil, which provide omega-3s in triglyceride form (SI 2007). Omega-3s obtained from eating fatty fish such as mackerel, salmon, and albacore provide some omega-3 in phospholipid from (SI 2007). Krill oil is extracted from Antarctic krill species Euphausia superba Dana, which is rich in omega-3. Moreover, the omega-3 in krill oil is mainly in the omega-3 phospholipid form, primarily as phosphatidylcholine, which research suggests is the preferred dietary supplement form when compared to omega-3 in triglyceride form (Aker 2009).

The human body contains large amounts of fatty acids. A general distinction can be made: phospholipid fatty acids are key structural and functional components of cells throughout the body (Aker 2009, Hanahan 1997), whereas triglycerides are chiefly used for production of metabolic energy and stored in adipose tissue cells (Hanahan 1997). Because some omega-3 and omega-6 fatty acids cannot be synthesized in the body, or are synthesized in lower amounts than demand, dietary intake of the essential fatty acids influences their relative concentration in cell membrane and adipose tissue storage (Aker 2009, Kidd 2007).

 
b. Absorption/Uptake

The current Western diet provides only small amounts of phospholipids; dietary phospholipids represent only 5% of total lipid uptake, of which very little is in the form of omega-3 phospholipids (Aker 2009). The digestion and absorption of phospholipids and triglycerides follows two different pathways each using unique digestive enzymes.

Triglycerides – the form of omega-3s in fish oils – are composed of a glycerol backbone with each carbon attached to a fatty acid. Digestion and absorption of triglycerides (fats) is a multi-step process: 1) lipolysis; 2) micellar solubilization of lipolysis products; 3) uptake of lipolysis products across intestinal cell membranes; 4) intracellular reseterification into triglycerides; 5) chylomicron formation; and 6) release of chylomicrons into the lymphatic system (Borgstrom 1957; Borgstrom 1974; Friedman 1980; Gangl 1975; Ockner 1974; Wells 1983).

In the gut lumen, bile acids (which have a hydrophobic and hydrophilic part) help in the emulsification process by "coating" the triglyceride and promoting the formation of smaller droplets. These droplets can then be attacked by enzymes such as pancreatic lipases and fatty acids are released. This results in three free fatty acids and one glycerol molecule per triglyceride or two free fatty acids and one monoglyceride per triglyceride. These products are still associated with bile salt and thus small micelles can be formed that are taken up by the epithelial cells. Once inside epithelial cells, triglycerides are put back together again, packaged into chylomicrons and transported into the blood via the lymphatic system. In spite of this laborious process, fats (and thus, fatty acids) of any form are well absorbed – over 90% of ingested fat finds its way into the bloodstream.

Omega-3 phospholipids follow simpler digestion and distribution routes than omega-3 triglycerides in the human body. Also, phospholipids are not dependent on bile for their absorption and do not need to be emulsified by bile salts. They can also be digested in their intact form or as lyso-phosphatidylcholine after digestion in the small intestine (Lagarde 2001, Ramirez 2001) (see Figure 5).

Figure 5.

Another absorption mechanism for phospholipids is direct uptake by intestinal epithelia for distribution via blood plasma (Lemaitre-Delaunay 1999). After absorption, phosphatidylcholine is incorporated into cell membranes and participates in fatty acid transport in blood and across membranes (Bernoud 1999, Hamazaki 2005, Kidd 2007, Lemaitre-Delaunay 1999; Nichols 1993; Thies 1994). Lyso-phosphatidylcholine is thought to impact the distribution of fatty acids to the body's organs and tissues because of its role in lipoprotein particles, which serve as vehicles that transport fatty acids via the blood serum (Lagarde 2001; Thies 1994). Transport of intact phospholipids into cell membranes is much more efficient than de novo synthesis of membrane phospholipids, a slow process involving miniscule amounts of at least 25 enzymes with associated proteins (Esko 1983, Langmuir 1993, Nichols 1993).

Omega-3 phospholipids may be considered a more efficient and preferred source of omega-3 for building and maintaining cell structures and promoting cellular functions than omega-3 triglycerides (Chandrasekar 1996, Venkatraman 1994). Omega-3 bioavailability is increased when delivered by phospholipids compared with other sources, due to more efficient absorption of omega-3 phospholipids in the small intestine (Aker 2009, Cansell 2003, Hargrove 2004, Lemaitre-Delaunay 1999, Maki 2009, Ruggiero-Lopez 1994, Werner 2004).

Krill has been known to enhance the efficiency of bioavailability of omega-3 fatty acids in humans due to its phospholipid form (Aker 2009). Using the same krill oil in MegaRed, Maki et al. (Maki 2009) showed a significant increase in plasma concentration of EPA and DHA in overweight and obese men and women after a 4 week supplementation with two grams of krill oil as compared to two grams of menhaden oil group. The daily intake of EPA provided in krill (216 mg) and menhaden oil (212 mg) supplements in this study was comparable. However, the DHA present in krill oil (90 mg/day) was approximately one half that provided in menhaden oil (178 mg/day). After four weeks, the mean plasma EPA concentration was somewhat higher in the krill oil group compared with the menhaden oil group (377 vs 293 µmol/L), and the mean plasma DHA concentrations were comparable (476 vs 478 µmol/L). Since krill oil DHA intake was half that of fish oil DHA intake, this study showed that krill oil is more efficient at increasing bioavailability of DHA into the bloodstream than fish oil. Furthermore, only plasma fatty acids were measured, and almost all fatty acids ingested end up in plasma. Other measurements of fatty acid uptake, such as tissue levels (erythrocyte membrane fatty acid amounts, or Omega-3 Index) would be expected to show larger differences between phospholipid and triglyceride omega-3 fatty acid levels. These results suggest that in humans, EPA and DHA from krill oil are absorbed more efficiently than from menhaden fish oil.

From a human study pending publication, Aker BioMarine kindly provided the results of an independently conducted human clinical trial measuring the Omega-3 Index (O3I). The Omega-3 Index is simply the percentage of fatty acids as EPA+DHA in red blood cell membranes. Thus, Omega-3 Index measures tissue uptake of omega-3 fatty acids. Tissue uptake of omega-3 fatty acids into cell membranes is a more relevant absorption measurement than plasma levels of fatty acids.

Sixty subjects were randomly assigned to either a control group (no fatty acid supplementation) or krill oil group (300 mg MegaRed daily) for 12 weeks. The control group was specifically not given a non-krill oil supplement since even that can change Omega-3 Index values. Thus, the control group is truly a dietary control group. The subjects (30 per group) were middle-aged, healthy Americans from Missouri. Results are shown in Figure 6.

Figure 6.

Percent Change in Omega-3 Index Levels from MegaRed in 30 American Subjects

After four weeks, MegaRed significantly increased Omega-3 Index values by 22% from baseline values (P<0.0001). Further significant increases at eight (23%) and twelve (37%) weeks were found. The control group also significantly increased Omega-3 Index values, but the comparison between control and MegaRed groups showed a significantly greater 2-2.5x increase in the MegaRed group (P<0.0026). Thus, MegaRed is well absorbed and taken up into tissue membranes, the active site for omega-3 fatty acid functions.

 
c. Biological effects of Krill Oil

The importance of omega-3 and omega-6 fatty acids is well known. But what do they really do? Both omega-3 and omega-6 fatty acids are essential for humans primarily as EPA and DHA. They have a critical role in membrane structure due to their non-linear structure. The bent structure of unsaturated fatty acids takes up more space in the cell membrane allowing for better fluidity (Kidd 2007, Lynch 1984, Ramirez 2001). Omega-3 and omega-6s are also precursors to eicosanoids, highly reactive and potent compounds, which often have opposing effects. The different eicosanoids are involved in smooth muscle cell regulation, platelet aggregation, vascular permeability and contractility, and influence the inflammatory process as well as the immune system (Das 2000, Goodnight 1992, Hirafuji 1998, Israel 1992, Pace-Asciak 1983; Pakala 1999).

The balance between omega-6 and omega-3 fatty acids in the diet is especially important because of their competition for the same enzymes and various biological functions (Das 1995, Das 2000, Harbige 2003, Luostarinen 1993, Wood 1984). When ingested, omega-3 and omega-6 fatty acids are incorporated into the n-2 position of membrane phospholipids. Omega-3s competitively inhibit omega-6 arachidonic acid, which is a precursor to pro-inflammatory metabolites such as prostaglandin E₂ (PGE₂) and the platelet aggregation promoting thromboxane A₂ (TXA₂), as well as proinflammatory leukotrienes (LTs) (Das 1985, Calder 2006, Caughey 1996, Endres 1989, Kelley 1999, Meydani 1991, Peterson 1998, Trebble 2003).

As a consequence of the enhanced cell membrane availability of omega-3 when delivered by phospholipids in humans, it is proposed that krill oil is a superior source of omega-3 for preventing cardiovascular diseases (Aker 2009, Tou 2007). Membrane phospholipid levels decrease and/or are deranged in diabetes, ischemic disease, cardiovascular disease, cancer, asthma and many other conditions (Gupta 1993). Thus, healthy membranes include maintenance of proper phospholipid levels.

 
d. Biological effects of Krill Oil: Animal & in vitro studies:

Krill and krill oil normally contain rich levels of astaxanthin esterified to fatty acids, accounting for the red color of krill oil (Aker 2009, Grynbaum 2005, Savage 1987, Takahashi 2003). Astaxanthin is recognized as an important antioxidant in biological systems, especially phospholipids and cell membranes (Guerin 2003, Higuera-Caipara 2006, Iwamoto 2000, Karppi 2007, Kurashige 1990, Lim 1992, Martinez 2008, McNulty 2008, Miki 1991, Naguib 1998, Naguib 2000, Nakagawa 1997, Tinkler 1994, Woodall 1997). In fact, astaxanthin was shown to be the most potent antiradical molecule by electron acceptance studies, compared to Vitamin C, Vitamin E and other carotenoids (Martinez 2008). In other words, astaxanthin is a membrane-spanning, chain-breaking antioxidant that does not break down into toxic species.

In order to assess the antioxidant activity of MegaRed®, the Total ORAC_FN test was performed by Brunswick Laboratories, the leader in antioxidant testing of foods and biological samples. Unlike the previous ORAC test, which measured only peroxyl radical quenching, the Total ORAC test measures activity against the five major classes of oxidative free radicals: peroxyl, hydroxyl, peroxynitrite, superoxide and singlet oxygen in both hydrophilic and lipophilic phases (http://brunswicklabs.com/FN_TOTALORAC.shtml). A single softgel of MegaRed showed 257 µmol TE, with activity against peroxyl (59%), hydroxyl (33%), peroxynitrite (1%) and singlet oxygen (7%) radicals (see Table below). Compared to a typical fish oil softgel (1200 mg fish oil with tocopherol added as an antioxidant), MegaRed showed 27 times greater total antioxidant capacity. 100% of the total antioxidant capacity of fish oil was against peroxyl radicals.

Total ORAC Results Listed as Per Serving
Material	Serving Size Description	Total ORAC (micromole Trolox Equivalents/serving)
MegaRed	One softgel (300 mg krill oil)	257
Fish Oil, 180/120	One softgel (1200 mg fish oil)	9.5

The substantial and comprehensive antioxidant activity of MegaRed helps explain its remarkable stability against oxidation, which is presumed to be accounted for by astaxanthin, the major component capable of antioxidant activity in krill oil. This means a long shelf life and minimal oxidation of oil (which would result in off odors and/or flavors) for MegaRed.

In certain animal models, after removing phosphatidylcholine from the diet, a significant reduction in the transport of fatty acids to tissues, accompanied by accumulation of fat in the liver, has been observed (Aker 2009). Studies have also shown a lowering of triglyceride fatty acids in animal heart and liver after krill oil supplementation. Batetta et al. (Batetta 2009) showed that obese rats fed krill or fish oil for 4 weeks had significantly decreased liver triglycerides but only the krill oil fed rats had lower heart triglycerides as compared to control rats. They also suggest that long-chain omega-3 fatty acids replace the inflammatory arachidonic acid in membrane phospholipids (Calder 2003, Calder 2006, Maki 2009), which is a substrate for cyclooxygenase and lipoxygenase and forms the less inflammatory vasoconstrictors thromboxane A3 and leukotriene B5 (Bagga 2003, Calder 2003, Calder 2006, Gewirtz 2002, Kelley 1985, Levy 2001, Needleman 1979, Prescott 1984, Serhan 2003, Vachier 2002). Venkatraman et al. (Venkatraman 1994) showed significantly lower concentrations of arachidonic acid and linoleic acid in hepatic microsome membranes and significantly higher levels of EPA and DHA in mice fed krill oil as compared to corn oil. The same trend was seen by Bridges et al. (Bridges 2010). Tandy et al. (Tandy 2009) also showed that rats fed a normal diet including krill oil demonstrated a significant reduction in liver weight and liver fat.

Other animal studies have also shown that krill oil supplementation has an anti-inflammatory effect on organs as well as specific inflammatory mediators. Chandrasekar et al. (Chandrasekar 1996) showed that mice fed krill oil enriched diets showed organ specific inflammatory mediator influence on transforming growth factor beta (TGFβ). Batetta et al. (Batetta 2009) also demonstrated that macrophages induced by lipopolysaccharide (LPS) secreted less tumor necrosis factor alpha (TNFα) in the presence of krill oil as compared to controls. Tandy et al. (Tandy 2009) also observed a significant decrease in the level of TNFα in inflamed rat liver after krill oil supplementation.

Krill oil has also been shown to possess antioxidant capabilities thanks in part to its high astaxanthin, vitamin A and E content (Hussein 2006, Kinumaki 1980, Miki 1998, Nicol 2000, Tou 2007). Venkatraman et al. (Venkatraman 1994) showed that krill oil significantly influenced the hepatic antioxidant enzymes of mice. The activities and genetic expression of catalase (CAT), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) significantly increased in hepatic microsomes. They also observed a significant decrease in peroxidation indices and generated thiobarbituric acid (TBARS) reactive substances.

In hyperlipidemia rat models krill oil significantly lowered triglycerides (Batetta 2009, Tou 2007, Zhu 2008), total cholesterol (Zhu 2008), and LDL-cholesterol levels (Tou 2007, Zhu 2008). The "good" HDL-cholesterol increased (Tou 2007, Zhu 2008) with consumption of omega-3 phospholipids as well.

Other studies also showed the importance of EPA and DHA for improvements of cardiovascular health such as lowering triglycerides (Batetta 2009, Kidd 2007), increasing HDL cholesterol (Tandy 2009, Werner 2004) and significant reductions in total cholesterol and LDL cholesterol after treatment with krill oil (Harris 1989, Sanders 1989, Zhu 2008).

 
e. Biological Effects of Krill Oil: Human studies

For this section, only human clinical studies using the same krill oil as used in MegaRed will be considered. From the previously discussed study pending publication, the Omega-3 Index in thirty middle-aged, healthy Americans was increased 22% after four weeks and 37% after 12 weeks from one MegaRed softgel daily (300 mg krill oil daily).

The Omega-3 Index is a powerful, emerging marker for predicting cardiovascular health (Harris 2004, Harris 2007, Harris 2008, Shearer 2009). Higher Omega-3 Indices are associated with less cardiovascular disease risk. Furthermore, the Omega-3 Index has been shown to be a better predictor of cardiovascular health than serum cholesterol or LDL cholesterol levels (Harris 2004, Harris 2007, Harris 2008, Shearer 2009). Thus, one serving per day of MegaRed provides significant cardiovascular health support.

Other human clinical trials on the krill oil used in MegaRed are completed or ongoing, using doses ranging from 300 mg to 8 grams daily. When results are released for presentation or publication, this website will be updated.