Randomised controlled trialindependent cross-checkfull text checked★ key study I-FSH-107 in-depth review
Salmon fed rapeseed oil still raised omega-3 levels in people
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.
Overview
de Roos B et al.. Eur J Nutr 2021 · PMID 33015732 · DOI 10.1007/s00394-020-02396-w
Two portions a week of salmon raised on rapeseed oil raised blood omega-3 almost as much as fish-oil-fed salmon and lowered blood fats; inflammation markers did not rise.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Compare health effects of differently fed farmed salmon.
- How was the study done?
18-week randomized trial.
- How many people, animals or samples were studied?
51 healthy adults.
- What was actually found?
Similar rise in omega-3 index; lower triglycerides with rapeseed-fed salmon.
- How large was the observed effect?
Omega-3 index +2.3 (FO) versus +2.0 (RO) points.
- What do the results mean in everyday life?
Modern farmed salmon still delivers omega-3 at two portions a week.
- What are the study's limitations?
Small, open-label, biomarkers only.
- What does it say about Elawady's specific claim?
Contradicts 'pro-inflammatory' and 'benefit disappears'.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Effects on heart attacks or joint disease.
Scientific in-depth review
1. Full reference
- Authors
- de Roos B et al.
- Journal
- Eur J Nutr
- Year
- 2021
- Identifier
- PMID 33015732 DOI 10.1007/s00394-020-02396-w
- Verification
- verified – PubMed efetch 2026-10-26; Crossref checked; full text PMC8137615 read (methods, results, tables, discussion, funding)
- Retracted
- no
- Corrections
- none
- Extent checked
- full text
- Conflicts of interest and funding
Scottish Government RESAS; salmon and feeds produced with Marine Harvest (MOWI) and BioMar; authors declare no conflicts
2. Research question
Does farmed salmon raised on rapeseed-oil feed give the same nutritional and cardiovascular benefits as salmon raised on fish-oil feed?
3. Study design and population
- Study design
- Randomised controlled trial – Randomized parallel controlled trial, 18 weeks (NCT01916434)
- Population
Healthy adults aged 35-75 years, BMI 25-35, Aberdeen
- Country
United Kingdom
- Period
2012-2014
- Sample size
51 completers (17 per arm)
- Inclusion and exclusion criteria
Excluded: anti-inflammatory drugs, supplements, diabetes, hypertension, CHD
4. Methods and endpoints
- Exposure / intervention
2 portions a week (~155 g each) of FO salmon (EPA+DHA 2.1 g/100 g; n-6 1.5, n-3 2.6 g/100 g) or RO salmon (EPA+DHA 0.9 g/100 g; n-6 2.1, n-3 1.7 g/100 g)
- Comparator
No additional salmon (habitual diet)
- Endpoints
Omega-3 index (primary); lipids, blood pressure, heart rate, hs-CRP, fibrinogen, sICAM-1, P-selectin, vitamin D, trace elements
- Statistical methods
ANCOVA adjusted for age, sex, BMI and baseline; Tukey post hoc tests
5. Actual results
- Results
Omega-3 index rose similarly with FO (+2.3 points) and RO salmon (+2.0 points) versus control (both p<0.05; FO versus RO not significant at 18 weeks). RO salmon lowered triacylglycerols (1.08 versus 1.31 mmol/L in controls at 18 weeks) and raised 25(OH)D3 versus control. hs-CRP at 18 weeks: 1.63 (FO), 1.31 (RO), 0.66 (control) mg/L, p treatment 0.596 (baseline imbalance p=0.036). Other markers unaffected.
- Absolute risks
not applicable
- Authors' conclusion
Rapeseed-oil-fed salmon increased the omega-3 index and vitamin D and lowered triacylglycerols; more sustainable feeds need not compromise health benefits at two portions a week.
6. Strengths
- Randomized, realistic intake
- Fillet composition measured
- 18-week duration
7. Weaknesses
- Small (n=51)
- Open-label
- Baseline imbalance in inflammatory markers
- Biomarkers, not clinical events
- Industry partners produced the fish and feed
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Open-label; baseline imbalance; powered only for the omega-3 index.
9. Assessment of the statistical interpretation
Secondary outcomes not powered; multiple outcomes without adjustment; the null CRP result is imprecise but shows no signal of increase. Recomputed weekly EPA+DHA: 6.6 g (FO) and 2.8 g (RO); fillet n-3:n-6 1.73 (FO) and 0.81 (RO) (stats/C-FSH-05_deroos2021.py).
10. Relevance to the specific claim
C-FSH-05: salmon with more n-6 than n-3 still raised omega-3 status and did not raise inflammatory markers.
11. Independent contrary findings
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Most direct human evidence that vegetable-oil-fed salmon is not 'pro-inflammatory' and keeps biomarker benefits.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | low |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- Because of the lower omega-3:omega-6 ratio, farmed salmon is converted from an anti-inflammatory into a pro-inflammatory meal, and the expected nutritional benefit disappears. – Studies contradicting or limiting the claim
- Because of its fatty-acid profile, farmed tilapia is an inflammation-promoting food for heart and joint patients. – Studies contradicting or limiting the claim