title: Comparison of bioavailability of krill oil versus fish oil and health effect.
abstract: BACKGROUND
  The aim of this review is to summarize the effects of krill oil (KO) or fish oil (FO) on eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) incorporation in plasma phospholipids or membrane of red blood cells (RBCs) as shown in human and animal studies. Furthermore, we discuss the findings in relation to the possible different health effects, focusing on lipids, inflammatory markers, cardiovascular disease risk, and biological functions of these two sources of long-chain n-3 polyunsaturated fatty acids (PUFAs).
  
  
  METHODS
  A literature search was conducted in PubMed in January 2015. In total, 113 articles were identified, but based on selection criteria, 14 original papers were included in the review.
  
  
  RESULTS
  Studies on bioavailability of EPA and DHA from KO and FO in humans and animals are limited and the interpretation is difficult, as different amounts of EPA and DHA have been used, duration of intervention differs, and different study groups have been included. Two human studies--one postprandial study and one intervention study--used the same amount of EPA and DHA from KO or FO, and they both showed that the bioavailability of EPA and DHA from KO seems to be higher than that from FO. Limited effects of KO and FO on lipids and inflammatory markers in human and animal studies were reported. Gene expression data from animal studies showed that FO upregulated the cholesterol synthesis pathway, which was the opposite of the effect mediated by KO. KO also regulated far more metabolic pathways than FO, which may indicate different biological effects of KO and FO.
  
  
  CONCLUSIONS
  There seems to be a difference in bioavailability of EPA and DHA after intake of KO and FO, but more studies are needed before a firm conclusion can be made. It is also necessary to document the beneficial health effects of KO with more human studies and to elucidate if these effects differ from those after regular fish and FO intake.
authors.affiliation: Department of Health, Nutrition and Management, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, Oslo, Norway.
authors.forename: Stine M
authors.initials: SM
authors.lastname: Ulven
authors.affiliation: Department of Nutrition, Institute for Basic Medical Sciences, University of Oslo, Oslo, Norway.
authors.forename: Kirsten B
authors.initials: KB
authors.lastname: Holven
mesh_terms: D000818:Animals; D001682:Biological Availability; D002318:Cardiovascular Diseases / Q000209:etiology / Q000517:prevention & control*; D019587:Dietary Supplements; D004281:Docosahexaenoic Acids / Q000493:pharmacokinetics; D015118:Eicosapentaenoic Acid / Q000493:pharmacokinetics; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D033201:Euphausiacea / Q000737:chemistry*; D005395:Fish Oils / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D006801:Humans; D009821:Oils / Q000008:administration & dosage / Q000493:pharmacokinetics*; D065840:Protective Factors; D012307:Risk Factors
chemical_list: D005395:Fish Oils; D009821:Oils; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid
keywords: animal studies; cardiovascular disease; gene expression; human studies; inflammation; lipid metabolism; long-chain polyunsaturated fatty acids