British Journal of Nutrition

Human and Clinical Nutrition

Oxidised fish oil does not influence established markers of oxidative stress in healthy human subjects: a randomised controlled trial

Inger Ottestada1a2, Gjermund Vogta3, Kjetil Retterstøla4, Mari C. Myhrstada1, John-Erik Haugena3, Astrid Nilssona3, Gitte Ravn-Harena5, Berit Nordvia6, Kirsti W. Brønnera6, Lene F. Andersena2, Kirsten B. Holvena2 and Stine M. Ulvena1 c1

a1 Faculty of Health, Nutrition and Management, Akershus University College, PO Box 423, 2001 Lillestrøm, Norway

a2 Department of Nutrition, Institute for Basic Medical Sciences, University of Oslo, PO Box 1046, Blindern, 0317 Oslo, Norway

a3 Nofima Mat AS, Osloveien 1, 1430 Ås, Norway

a4 Lipid Clinic, Medical Department, Rikshospitalet-Oslo University Hospital, PO Box 4950, Nydalen, 0424 Oslo, Norway

a5 Department of Toxicology and Risk Assessment, Technical University of Denmark, National Food Institute, Mørkhøj Bygade 19, 2860 Søborg, Denmark

a6 TINE SA, Centre for Research and Development, PO Box 7, Kalbakken, N-0902 Oslo, Norway


Intake of fish oil reduces the risk of CHD and CHD deaths. Marine n-3 fatty acids (FA) are susceptible to oxidation, but to our knowledge, the health effects of intake of oxidised fish oil have not previously been investigated in human subjects. The aim of the present study was to investigate markers of oxidative stress, lipid peroxidation and inflammation, and the level of plasma n-3 FA after intake of oxidised fish oil. In a double-blinded randomised controlled study, healthy subjects (aged 18–50 years, n 54) were assigned into one of three groups receiving capsules containing either 8 g/d of fish oil (1·6 g/d EPA+DHA; n 17), 8 g/d of oxidised fish oil (1·6 g/d EPA+DHA; n 18) or 8 g/d of high-oleic sunflower oil (n 19). Fasting blood and morning spot urine samples were collected at weeks 0, 3 and 7. No significant changes between the different groups were observed with regard to urinary 8-iso-PGF; plasma levels of 4-hydroxy-2-hexenal, 4-hydroxy-2-nonenal and α-tocopherol; serum high sensitive C-reactive protein; or activity of antioxidant enzymes in erythrocytes. A significant increase in plasma level of EPA+DHA was observed in both fish oil groups, but no significant difference was observed between the fish oil groups. No changes in a variety of in vivo markers of oxidative stress, lipid peroxidation or inflammation were observed after daily intake of oxidised fish oil for 3 or 7 weeks, indicating that intake of oxidised fish oil may not have unfavourable short-term effects in healthy human subjects.

(Received June 03 2011)

(Revised September 07 2011)

(Accepted September 08 2011)

(Online publication December 05 2011)


c1 Corresponding author: S. M. Ulven, fax +47 64849001, email


Abbreviations: 4-HHE, 4-hydroxy-2-hexenal; 4-HNE, 4-hydoxy-2-nonenal; AV, anisidine value; CAT, catalase; CRP, C-reactive protein; E%, percentage of energy; FA, fatty acids; FO, 8 g/d of fish oil; GPx, glutathione peroxidase; GR, glutathione reductase; GSH, glutathione; HOSO, 8 g/d of high-oleic sunflower oil; oxFO, 8 g/d of oxidised fish oil; PV, peroxide value; tGSH, total glutathione