Flaxseed Oil Scientific References and Clinical Studies

How This Flaxseed Oil Scientific Reference Library Is Organized

The library groups sources by evidence tier: systematic reviews, meta-analyses, randomized controlled trials (RCTs), observational studies, pharmacokinetic work, safety studies, mechanistic studies and preclinical research. Primary research reports original data; secondary research (reviews and meta-analyses) pools or appraises primary studies.

One rule runs through every section: flaxseed oil is not whole flaxseed, defatted meal, lignan extract, isolated ALA or marine EPA/DHA. Whole flaxseed contributes fiber and lignans that the oil lacks, so results from one preparation must not be assumed to carry over to another. Where a review mixes preparations, this page says so and reports flaxseed-oil subgroup results separately.

For each entry the library records year, design, population, dose, duration, outcome and limitations, and marks anything unavailable as "Not reported" rather than guessing. Inclusion does not mean a study is high quality or has been independently replicated.

Scope of this edition: entries were verified in a targeted search, not a systematic one (see the update log). Sections with no verified entry say so instead of being padded.

Systematic Reviews of Flaxseed Oil Research

Two reviews below are best read as systematic reviews with quantitative synthesis; they are described under meta-analyses because they pool data. Both identify flaxseed oil as a distinct intervention:

• Yang et al., 2021 (Nutrition & Metabolism 18:91) searched five databases to January 2020 and compared whole flaxseed, flaxseed oil and lignans in people with dyslipidemia-related conditions. Flaxseed oil was tested in 10 of the 31 included RCTs, at 0.4 to 24 g/day. The authors noted that control oils rich in monounsaturated or n-6 polyunsaturated fat may have masked lipid effects.
• Rahimlou et al., 2019 (Advances in Nutrition) and Ren et al., 2016 (Nutrients) reviewed flaxseed and its derivatives (whole seed, oil, lignans) for inflammatory markers. They do not isolate flaxseed oil as their main question, so treat them as indirect evidence.

Flaxseed Oil Meta-Analyses

Direct, flaxseed-oil-specific meta-analyses exist for a few outcomes only; most pooled work covers mixed flaxseed products.

Flaxseed-oil-specific

• Oxidative stress (2021). A meta-analysis of RCTs in adults examined malondialdehyde (MDA), glutathione (GSH) and total antioxidant capacity (TAC) after flaxseed oil. The authors concluded that flaxseed oil might support antioxidant defenses and reduce oxidative stress. Its risk-of-bias table lists eight trial entries, including Rezaei 2020 and Raygan 2019, with varying bias ratings. Pooled estimates are not reproduced here because they were not verified in this pass; consult the record.
• Lipid profile (2026). A systematic review and dose-response meta-analysis in the Avicenna Journal of Phytomedicine analyzed 36 RCTs with 1,959 participants, searching to February 2025. Non-linear dose-response associations were reported between flaxseed oil dose and LDL-C (p = 0.039) and between ALA intake and LDL-C (p = 0.039) and total cholesterol (p = 0.027). Pooled mean differences were not verified here.

Mixed-product, with flaxseed-oil subgroups

• Yang 2021: flaxseed oil showed no lipid-lowering effect, but reduced IL-6 (-0.35 pg/mL, 95% CI -0.67 to -0.03) and hs-CRP (-1.54 mg/L, 95% CI -2.59 to -0.49) and waist circumference (-1.61 cm, 95% CI -2.69 to -0.53). Overall heterogeneity for lipid outcomes was very high (I² above 90%), publication bias was suggested for total cholesterol and LDL-C, standard deviations were partly imputed, and only English-language studies were included.
• Ren 2016 (20 studies; PROSPERO CRD42016034184) found insufficient evidence that flaxseed or its derivatives lower CRP. Rahimlou 2019 (32 articles) reported lower hs-CRP and TNF-alpha but no change in IL-6 or CRP for flaxseed products overall.

The subgroup findings are statistically significant in the pooled data, but their clinical meaning is unproven, and the products pooled differ in dose, comparator and population.

Randomized Controlled Trials of Flaxseed Oil

The trials below were identified through the Yang 2021 review and its reference list; bibliographic details are taken from that list and summarized in the evidence table. Doses and comparators come from the review's extraction table, not from independent reading of each full text.

• Rezaei 2020 (NAFLD, 12 weeks): flaxseed oil 20 mL/day with a weight-loss program versus sunflower oil; double-blind. The title reports improved fatty liver grade.
• Raygan 2019 (type 2 diabetes with coronary heart disease, 12 weeks): small-dose flaxseed oil (ALA 0.4 g/day) in a double-blind, placebo-controlled trial that also included a fish oil arm.
• Akrami 2018 (metabolic syndrome, 7 weeks): flaxseed oil 25 mL/day versus sunflower oil.
• Paschos 2007 and Rallidis 2003 (dyslipidemic men, 12 weeks): about 15 mL/day (ALA roughly 8 g) versus safflower oil. Rallidis 2003 reports decreases in CRP, serum amyloid A and IL-6 with dietary ALA.
• Dittrich 2015 (hypertriglyceridemia, 10 weeks, crossover): flaxseed oil 10 g/day (ALA 7 g) versus sunflower oil.
• Yang 2019 (hypertension with abdominal obesity, 13 weeks): 4 g/day (ALA 2.5 g) versus corn oil. de Oliveira 2017 (older adults with overweight/obesity, 13 weeks): 30 mL/day (ALA 24 g) versus sunflower oil.
• Gillingham 2011 (hypercholesterolemia, 4 weeks, crossover) used a high-oleic canola and flaxseed oil combination; the flaxseed oil dose is not reported in the extracted table.

Common limitations: small samples (roughly 15 to 90 completers), short durations, varied comparator oils, and surrogate biomarker endpoints. A biomarker change is not the same as a patient-important outcome, and adverse events were not extracted in this pass.

Observational Human Studies

No observational study was verified in this pass that isolates flaxseed oil exposure. Cohort data on dietary ALA (for example the meta-analysis by Pan et al., American Journal of Clinical Nutrition 2012) reflect ALA from many foods, not flaxseed oil, and are subject to confounding. They are indirect evidence and are not equivalent to RCT evidence.

Flaxseed Oil Pharmacokinetic Studies

No flaxseed-oil-specific pharmacokinetic trial was verified in this pass. For background on how ALA is absorbed, incorporated into tissues and converted to longer-chain omega-3 fatty acids, see the review by Baker et al. (Progress in Lipid Research 2016). Conversion of ALA to EPA and DHA is generally described as limited and variable between individuals, so a rise in ALA intake should not be assumed to produce predictable EPA or DHA increases, and blood fatty-acid changes are not clinical outcomes.

Flaxseed Oil Safety and Toxicology Studies

No dedicated safety or toxicology study was verified here. Trial reports in the table may contain adverse-event data, which should be extracted from full texts. Short-term trial tolerability does not establish long-term safety, and animal findings should not be transferred to humans. See the companion safety and interactions pages.

Mechanistic Studies on Flaxseed Oil

Proposed mechanisms include ALA competing with linoleic acid for shared metabolic enzymes, shifting eicosanoid production, and antioxidant effects on lipid peroxidation. Yang 2021 discusses these ideas as explanations for the oil's inflammatory-marker findings; they remain hypotheses. Mechanistic plausibility does not establish a clinically meaningful benefit, and each mechanistic entry should be labeled human, animal or in vitro.

Preclinical Flaxseed Oil Research

• Hussein et al. (rats with diet-induced hypercholesterolemia): flaxseed oil 270 mg/kg/day orally, sampled at 2, 4 and 6 weeks, was reported to lower TNF-alpha, IL-6 and lipid peroxidation markers and improve hepatic antioxidant status. Journal and year were not retrieved. Rodent finding; human relevance unproven.
• Gulcin et al., 2025 (Molecules 30(16):3384): in vitro antioxidant and enzyme-inhibition assays of a steam-distilled flaxseed oil fraction. Because this is a laboratory preparation, it may differ from dietary oils.

Flaxseed Oil Clinical Studies: Evidence Table

Year	Authors	Study design	Population/model	Sample size	Intervention	Dose	Duration	Outcome	Main findings	Limitations	Source
2021	Yang C, Sun G, et al.	Systematic review and meta-analysis	Dyslipidemia-related diseases	31 RCTs, 1,698	Whole flaxseed, oil, lignans	Oil: 0.4 to 24 g/day	2 weeks to 12 months	Lipids, inflammation, anthropometrics	Oil: no lipid effect; IL-6 -0.35 pg/mL, hs-CRP -1.54 mg/L, waist -1.61 cm	High heterogeneity; control oils; English only	DOI
2021	See record	Systematic review and meta-analysis	Adults	8 trial entries in risk-of-bias table	Flaxseed oil	Not verified	Not verified	MDA, GSH, TAC	Authors report possible antioxidant benefit; pooled estimates not verified	Mixed bias ratings; small trial set	DOI
2026	See record	Systematic review and dose-response meta-analysis	Adults	36 RCTs, 1,959	Flaxseed oil	Dose-response modeled	Not reported here	Lipid profile	Non-linear dose links to LDL-C and TC	Pooled estimates not verified	Journal page
2016	Ren GY, et al.	Meta-analysis	Adults	20 studies	Flaxseed and derivatives	Varies	Varies	CRP	Insufficient evidence of CRP reduction	Mixed products	PMC
2019	Rahimlou M, et al.	Meta-analysis	Adults 18 to 70 y	32 articles	Flaxseed and derivatives	Varies	Varies	hs-CRP, TNF-alpha, IL-6, CRP	Lower hs-CRP and TNF-alpha; no IL-6 or CRP change	Mixed products; heterogeneity	PMC
2020	Rezaei S, et al.	RCT, double-blind	NAFLD	57 of 68 completed	Flaxseed oil vs sunflower oil, with weight loss	20 mL/day	12 weeks	Fatty liver grade	Title reports improved grade	Small; surrogate outcome	PubMed search
2019	Raygan F, et al.	RCT, double-blind, placebo-controlled	T2DM with CHD	55 of 60	Flaxseed oil vs placebo (fish oil arm)	ALA 0.4 g/day	12 weeks	Cardiovascular markers	Not extracted	Small; low dose	PubMed search
2018	Akrami A, et al.	RCT	Metabolic syndrome	52 of 60	Flaxseed vs sunflower oil	25 mL/day	7 weeks	Glucose, lipids, BP, lipid peroxidation	Not extracted	Short; small	PubMed search
2007	Paschos GK, et al.	RCT	Dyslipidemic men	87	Flaxseed vs safflower oil	15 mL/day (ALA 8 g)	12 weeks	Adiponectin	Not extracted	Men only	PubMed search
2003	Rallidis LS, et al.	RCT	Dyslipidemic men	76 of 90	Linseed vs safflower oil	15 mL/day (ALA 8.1 g)	12 weeks	CRP, SAA, IL-6	Title reports decreases	Men only; biomarkers	PubMed search
2015	Dittrich M, et al.	RCT, crossover	Hypertriglyceridemia	49 of 59	Flaxseed vs sunflower oil	10 g/day (ALA 7 g)	10 weeks	Triglycerides and related markers	Not extracted	Crossover; small	PubMed search
2019	Yang B, et al.	RCT	Hypertension with abdominal obesity	66 of 73	Flaxseed vs corn oil	4 g/day (ALA 2.5 g)	13 weeks	Cardiometabolic profile	Not extracted	Small	PubMed search
2017	de Oliveira PA, et al.	RCT	Older adults, overweight or obese	76 of 79	Flaxseed vs sunflower oil	30 mL/day (ALA 24 g)	13 weeks	Atherosclerosis markers	Not extracted	Small	PubMed search
2011	Gillingham LG, et al.	RCT, crossover	Hypercholesterolemia	36 of 39	High-oleic canola plus flaxseed oil	Not reported	4 weeks	Serum lipids, inflammation	Not extracted	Combined oils	PubMed search
Not reported	Hussein SA, et al.	Preclinical	Hypercholesterolemic rats	Not reported	Flaxseed oil	270 mg/kg/day	6 weeks	Inflammation, oxidative stress	Lower TNF-alpha, IL-6, MDA	Rodent; journal not retrieved	Record
2025	Gulcin I, et al.	In vitro	Steam-distilled oil	Not applicable	Flaxseed oil fraction	Not applicable	Not applicable	Antioxidant, enzyme inhibition	Activity in assays	Not a human study	DOI

"Not extracted" means the outcome result was not verified in this pass. "PubMed search" links open a title-based search, not a confirmed record page.

Flaxseed Oil Research Papers: DOI, PubMed and Official Links

To retrieve original flaxseed oil research papers, start with PubMed for the abstract and PMID, then follow the DOI to the publisher. Cochrane Library covers Cochrane reviews, and ClinicalTrials.gov lists registered trials. A registered trial is not a completed or published one; check for results or a linked publication. If full text is paywalled, link to the official record and do not imply open access. Never accept a DOI from a secondary source without resolving it at doi.org.

How to Interpret the Strength of Flaxseed Oil Evidence

Randomized trials best support causal claims when randomization, allocation concealment and blinding are sound and the comparator is appropriate. Here comparators matter: sunflower or safflower oil (rich in n-6 fat) may act differently from a neutral placebo. Meta-analyses add power but inherit bias and heterogeneity from their trials; high I² means pooled averages may hide real differences. Observational studies show associations vulnerable to confounding. Human mechanistic studies, animal experiments and in vitro work generate hypotheses and cannot stand in for clinical outcomes.

Statistical significance is not clinical significance: a 0.35 pg/mL IL-6 difference may be real yet have no known effect on patient outcomes. No formal GRADE ratings are assigned here because GRADE was not applied transparently. Direct flaxseed oil evidence is kept apart from indirect evidence on whole flaxseed, lignans, isolated ALA and other omega-3 sources.

Research Limitations and Evidence Gaps

• Few flaxseed-oil-specific trials per outcome, mostly small and short.
• Differences in oil composition, processing and storage; many trials do not report them.
• Wide variation in dose (0.4 to 24 g/day), duration, comparator and population.
• Heavy reliance on biomarkers rather than patient-important outcomes.
• Sparse long-term safety data and possible publication bias.
• Limited generalizability across ages and health conditions.
• Gaps in this edition: no verified observational, pharmacokinetic or dedicated safety entries.

Frequently Asked Questions About Flaxseed Oil Research

1. Where can I find scientific studies on flaxseed oil? PubMed, Cochrane Library, ClinicalTrials.gov and publisher sites; search "flaxseed oil" and "linseed oil".

2. How does flaxseed oil research differ from whole flaxseed research? Whole flaxseed adds fiber and lignans; results do not transfer automatically to the oil.

3. Are RCTs available for flaxseed oil? Yes, mostly small, short trials in specific populations, as in the table above.

4. How can I verify a study's DOI? Enter it at doi.org and confirm the title, authors and journal match the PubMed record.

5. Are all published studies equally reliable? No; design, sample size, blinding, comparator and bias risk differ.

6. Does a mechanistic study prove a health benefit? No; it shows a plausible pathway only.

7. How do I identify the dose in a trial? Check the methods section and the intervention table; note whether dose is given as oil volume, weight or ALA content.

8. Where can I find free full texts? PubMed Central and open-access journals; an official record link does not guarantee free access.

9. How often should a reference library be updated? On a stated schedule and whenever major new trials or meta-analyses appear.

10. How should conflicting findings be interpreted? Compare designs, doses, comparators and populations, and weigh higher-quality evidence more, without forcing a single conclusion.

Scientific References and Update Log

Systematic reviews and meta-analyses

1. Yang C, Xia H, Wan M, Lu Y, Xu D, Yang X, Yang L, Sun G. Comparisons of the effects of different flaxseed products consumption on lipid profiles, inflammatory cytokines and anthropometric indices in patients with dyslipidemia related diseases: systematic review and a dose-response meta-analysis of randomized controlled trials. Nutr Metab (Lond). 2021;18:91. doi:10.1186/s12986-021-00619-3
2. Flaxseed Oil Supplementation Augments Antioxidant Capacity and Alleviates Oxidative Stress: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. 2021;2021:4438613. doi:10.1155/2021/4438613 (authors and journal title to be confirmed on the record: https://pmc.ncbi.nlm.nih.gov/articles/PMC8437595/)
3. Effect of flaxseed oil supplementation on lipid profile in adults: A systematic review and dose-response meta-analysis of randomized controlled trials. Avicenna J Phytomed. 2026;16(4):597 (authors not retrieved). https://ajp.mums.ac.ir/article_26733.html
4. Ren GY, Chen CY, Chen GC, Chen WG, Pan A, Pan CW, Zhang YH, Qin LQ, Chen LH. Effect of flaxseed intervention on inflammatory marker C-reactive protein: a systematic review and meta-analysis of randomized controlled trials. Nutrients. 2016;8:136. https://pmc.ncbi.nlm.nih.gov/articles/PMC4808865
5. Rahimlou M, Jahromi NB, Hasanyani N, Ahmadi AR. Effects of flaxseed interventions on circulating inflammatory biomarkers: a systematic review and meta-analysis of randomized controlled trials. Adv Nutr. 2019;10:1108-19. https://pmc.ncbi.nlm.nih.gov/articles/PMC6855939/
6. Pan A, Chen M, Chowdhury R, Wu JHY, Sun Q, Campos H, Mozaffarian D, Hu FB. Alpha-linolenic acid and risk of cardiovascular disease: a systematic review and meta-analysis. Am J Clin Nutr. 2012;96:1262-73. (Indirect evidence; ALA from all sources.)

Randomized controlled trials (citations as listed in reference 1)

7. Rezaei S, Sasani MR, Akhlaghi M, Kohanmoo A. Flaxseed oil in the context of a weight loss program ameliorates fatty liver grade in patients with non-alcoholic fatty liver disease: a randomized double-blind controlled trial. Br J Nutr. 2020;123.
8. Raygan F, Taghizadeh M, Mirhosseini N, et al. A comparison between the effects of flaxseed oil and fish oil supplementation on cardiovascular health in type 2 diabetic patients with coronary heart disease: a randomized, double-blinded, placebo-controlled trial. Phytother Res. 2019;33:1943-51.
9. Akrami A, Nikaein F, Babajafari S, Faghih S, Yarmohammadi H. Comparison of the effects of flaxseed oil and sunflower seed oil consumption on serum glucose, lipid profile, blood pressure, and lipid peroxidation in patients with metabolic syndrome. J Clin Lipidol. 2018;12:70-7.
10. Paschos GK, Zampelas A, Panagiotakos DB, et al. Effects of flaxseed oil supplementation on plasma adiponectin levels in dyslipidemic men. Eur J Nutr. 2007;46:315-20.
11. Rallidis LS, Paschos G, Liakos GK, Velissaridou AH, Anastasiadis G, Zampelas A. Dietary alpha-linolenic acid decreases C-reactive protein, serum amyloid A and interleukin-6 in dyslipidaemic patients. Atherosclerosis. 2003;167:237-42.
12. Dittrich M, Jahreis G, Bothor K, et al. Benefits of foods supplemented with vegetable oils rich in alpha-linolenic, stearidonic or docosahexaenoic acid in hypertriglyceridemic subjects: a double-blind, randomized, controlled trial. Eur J Nutr. 2015;54:881-93.
13. Yang B, Shi MQ, Li ZH, et al. Effects of n-3 fatty acid supplements on cardiometabolic profiles in hypertensive patients with abdominal obesity in Inner Mongolia: a randomized controlled trial. Food Funct. 2019;10:1661-70.
14. de Oliveira PA, Kovacs C, Moreira P, Magnoni D, Saleh MH, Faintuch J. Unsaturated fatty acids improve atherosclerosis markers in obese and overweight non-diabetic elderly patients. Obes Surg. 2017;27:2663-71.
15. Gillingham LG, Gustafson JA, Han SY, Jassal DS, Jones PJH. High-oleic rapeseed (canola) and flaxseed oils modulate serum lipids and inflammatory biomarkers in hypercholesterolaemic subjects. Br J Nutr. 2011;105:417-27.

Pharmacokinetic and mechanistic background

16. Baker EJ, Miles EA, Burdge GC, Yaqoob P, Calder PC. Metabolism and functional effects of plant-derived omega-3 fatty acids in humans. Prog Lipid Res. 2016;64:30-56.

Preclinical and in vitro

17. Hussein SA, El Senosi YA, Hassanein MR, et al. Evaluation of the protective role of flaxseed oil on inflammatory mediators, antioxidant defense system and oxidative stress of liver tissue in hypercholesterolemic rats. https://newstaff.bu.edu.eg/publication/samyaziza1/abstract/31436 (journal and year not retrieved)
18. Gulcin I, Mutlu M, Bingol Z, Ozden EM, Mirzaee Z, et al. Antioxidant activity and phytochemical profiling of steam-distilled oil of flaxseed (Linum usitatissimum): therapeutic targeting against glaucoma, oxidative stress, cholinergic imbalance, and diabetes. Molecules. 2025;30(16):3384. doi:10.3390/molecules30163384