Fish oil (FO) supplementation reduces the risk of CVD. However, it is not known if FO of different qualities have different effects on lipoprotein subclasses in humans. We aimed at investigating the effects of oxidized FO and high-quality FO supplementation on lipoprotein subclasses and their lipid concentrations in healthy humans. In all, fifty-four subjects completed a double-blind randomized controlled intervention study. The subjects were randomly assigned to receive high-quality FO (n 17), oxidized FO (n 18) or high-oleic sunflower oil capsules (HOSO, n 19) for 7 weeks. The concentration of marine n-3 fatty acids was equal in high-quality FO and oxidized FO (1•6 g EPA + DHA/d). The peroxide value (PV) and anisidine value (AV) were 4 mEq/kg and 3 in high-quality FO and HOSO, whereas the PV and AV in the oxidized FO were 18 mEq/kg and 9. Blood samples were collected at baseline and end of study. NMR spectroscopy was applied for the analysis of lipoprotein subclasses and their lipid concentrations. High-quality FO reduced the concentration of intermediate-density lipoprotein (IDL) particles and large, medium and small LDL particles, as well as the concentrations of total lipids, phospholipids, total cholesterol, cholesteryl esters and free cholesterol in IDL and LDL subclasses compared with oxidized FO and HOSO. Hence, high-quality FO and oxidized FO differently affect lipid composition in lipoprotein subclasses, with a more favorable effect mediated by high-quality FO. In future trials, reporting the oxidation levels of FO would be useful.
Healthy, non-smoking men and women aged 18–50 years who met the eligibility criteria were included in this study. In brief, the exclusion criteria were chronic illness, pregnancy, lactation, BMI ≥30 kg/m2, hypertension (≥
160/100 mmHg) and fasting serum levels of total cholesterol>7.5mΜ, TAG >4.0 mmol/l, glucose >6.0 mmol/l and C-reactive protein >10 mg/l, as well as serum levels of thyroxine stimulating hormone, free T3 and free T4 outside the reference ranges. A more detailed description of participant recruitment and enrolment, inclusion and exclusion criteria, protocol, study products and compliance is given elsewhere.
Intake of oxidized FO and high-quality FO differently affect lipid composition in lipoprotein subclasses, with a more favorable effect mediated by high-quality FO. Hence, in future trials investigating the health beneficial effects of FO supplementation, it would be useful to report the oxidation levels of the oils consumed.