The nutritional and cardiovascular health benefits of rapeseed oil-fed farmed salmon in humans are not decreased compared with those of traditionally farmed salmon: a randomized controlled trial

Abstract

Purpose: Farmed fish are increasingly raised on feeds containing vegetable oils, which affects their composition and possibly health properties. We investigated the effects of consuming farmed salmon, raised on different feeding regimes, on nutrient status and health outcomes in healthy subjects.

Methods: Salmon were grown on feeds containing mainly fish oil (FO) or rapeseed oil (RO), resulting in an eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) content of fillets of 2.1 or 0.9 g/100 g, respectively. In a randomized parallel controlled trial, 51 healthy subjects were allocated to consume 2 portions/week of FO salmon (n = 17), RO salmon (n = 17) or no additional salmon (Control, n = 17) as part of their habitual diet, for 18 weeks. We collected blood at 0, 9 and 18 weeks to measure omega-3 index (O3I) in red blood cells, plasma markers of cardiovascular risk, serum 25(OH)-vitamin D3 (25(OH)D3) and plasma trace elements.

Results: After 18 weeks, O3I was similarly increased in subjects consuming 2 portions/week of FO or RO salmon compared to control (both p < 0.05). Serum 25(OH)D3 was significantly higher, whereas plasma triacylglycerols were significantly lower in subjects consuming RO salmon compared to control (both p < 0.05). Heart rate was significantly lower in subjects consuming FO salmon after 9 weeks, compared to control (p < 0.01). Salmon consumption did not affect other markers.

Conclusion: Consuming two portions/week of salmon raised on rapeseed oil rather than fish oil increased the O3I and vitamin D status, and decreased plasma triacylglycerols. These outcomes endorse opportunities for developing more sustainable feeds within aquaculture food systems.

Clinical trial registry: This trial was registered at clinicaltrials.gov as NCT01916434.

Keywords: Cardiovascular health; Farmed fish; Fish feeds; Micronutrients; Omega-3 index; Vitamin D.

Conflict of interest statement

None of the authors reported a conflict of interest.

Figures

Fig. 1

Flow chart of participant recruitment

Fig. 2

Changes in RBC fatty acid composition upon consumption of 2 portions of FO or RO salmon per week or no additional salmon (control), after 9 and 18 weeks. Data are means ± SEM. a: Change in O3I from baseline at 9 weeks and 18 weeks for FO salmon (black), RO salmon (gray), control (white) groups; *p < 0.01 for differences from control group; #p < 0.05 for difference between FO and RO salmon groups. b: Correlation of changes in O3I with the intake of EPA + DHA per kg of body weight across the FO salmon (black), RO salmon (gray) and control (white) groups after 18 weeks of intervention. Changes in the abundance of individual fatty acids in RBC upon consumption of c: FO (black) or d: RO (gray) salmon for 18 weeks. *p < 0.05 for differences from control group; #p < 0.05 for differences between FO and RO salmon groups

Fig. 3

Predicted versus actual O3I (%). The predicted O3I = baseline O3I − the predicted change in O3I, with the latter being calculated with an algorithm based on studies with fish oil supplements (21): 2.60 + 0.921 × 1 – 0.842 × baseline O3I + 0.05 × (baseline O3I)2 + 0.0027 × [dose EPA + DHA in mg/day] – 0.000000471 × [dose EPA + DHA in mg/day]2. The dose of EPA + DHA/day used was 900 mg/day for the FO salmon group and 400 mg/day for the RO salmon group (see “Results”). Black circles represent the FO salmon group, gray circles the RO salmon group, and white circles the Control group. The solid line represents the line y = x, illustrating the ‘perfect prediction’. The dashed lines represent the best fit lines of the predicted compared with observed O3I values for the FO salmon group (black), the RO salmon group (dark gray) and the control group (light gray)