Flaxseed Oil
Linum usitatissimum oil
TL;DR
Flaxseed oil supplies ALA, which humans convert to EPA at roughly 5-8% and to DHA at under 1%. It is a reasonable vegan source of ALA itself, but a poor way to raise EPA and DHA — algal oil does that directly.
Ideal For
- Vegans and vegetarians wanting an ALA source
- Mildly elevated blood pressure, using whole flaxseed
- Constipation and cholesterol, where ground seed suits better
- Those who will not take marine oils
Avoid If
- Needing EPA and DHA specifically — use algal oil
- Bowel obstruction or stricture, with whole seed
- Hormone-sensitive cancers, regarding lignans, without advice
- On anticoagulants at high doses
Frequently Asked Questions
Overview
Flaxseed oil gets recommended as the plant alternative to fish oil, and the conversion arithmetic is the reason that recommendation only partly works. Alpha-linolenic acid must pass through delta-6 desaturase, elongase and delta-5 desaturase to become EPA, and then through a further elongation and peroxisomal beta-oxidation step to become DHA. Human tracer studies put ALA to EPA conversion at around 5-8% and ALA to DHA at under 1%, with women converting somewhat better than men because of oestrogen's effect on desaturase activity. High linoleic acid intake, which is the norm on Western diets, competes for the same enzymes and depresses conversion further. The practical consequence is that a tablespoon of flaxseed oil delivering roughly 7 g of ALA yields perhaps 350-560 mg of EPA equivalent and almost no DHA — not nothing, but not a fish oil substitute either. Where flaxseed does have independent evidence is blood pressure, with meta-analyses showing modest reductions, and whole ground flaxseed additionally supplies lignans and soluble fibre that lower LDL cholesterol, effects the oil alone does not provide. For vegans wanting EPA and DHA specifically, algal oil is the direct answer.
How It Works
- ALA converts to EPA at only 5-8%, to DHA at under 1%
- Delta-6 desaturase is shared with, and inhibited by, omega-6 intake
- Women convert somewhat better than men
- Lignans and fibre in whole flaxseed, not the oil, lower LDL
Quick Facts
- ALA to EPA conversion is only 5-8%
- ALA to DHA conversion is under 1%
- Omega-6 intake competes and lowers conversion further
- Ground seed, not oil, provides the lignans and fibre
Benefits & Outcomes
No linked outcomes yet. Research is ongoing.
Supporting Research5 studies
Consumption of Buglossoides arvensis seed oil is safe and increases tissue long-chain n-3 fatty acid content more than flax seed oil: results of a phase I randomised clinical trial
Lefort N, LeBlanc R, Giroux MA +1 more
Ahiflower oil raised eicosapentaenoic acid (EPA) and total long-chain n-3 content in blood and cells significantly more than flaxseed oil, consistent with stearidonic acid bypassing the rate-limiting delta-6-desaturase step. No adverse effects on safety biomarkers were seen. Docosahexaenoic acid (DHA) did not increase.
Effects of dietary hempseed oil on serum lipids and fatty acid composition in healthy adults: a randomised crossover trial
Schwab US, Callaway JC, Erkkila AT +3 more
Hempseed oil raised plasma gamma-linolenic acid and altered fatty acid composition but did not significantly improve total or LDL cholesterol compared with flaxseed oil.
Meta-analysis of the effects of flaxseed interventions on blood lipids
Pan A, Yu D, Demark-Wahnefried W +2 more
Significant reductions in cholesterol were observed with whole flaxseed and lignan supplements but not with flaxseed oil.
Effects of flaxseed supplements on blood pressure: A systematic review and meta-analysis of controlled clinical trials
Ursoniu S, Sahebkar A, Andrica F +2 more
Flaxseed supplementation significantly reduced diastolic blood pressure; systolic reductions were significant only in trials lasting 12 weeks or longer.
Potent antihypertensive action of dietary flaxseed in hypertensive patients (FlaxPAD)
Rodriguez-Leyva D, Weighell W, Edel AL +8 more
Systolic and diastolic blood pressure were roughly 10 and 7 mmHg lower in the flaxseed group than in the placebo group.
Safety Information
Potential Side Effects
Loose stools and gastrointestinal upset at higher doses. Rancid oil causes nausea and is common if storage is poor. Whole seed can worsen bloating.
Contraindications
Bowel obstruction or oesophageal stricture with whole or ground seed, which must be taken with adequate fluid. Caution with lignans in hormone-sensitive conditions.
Drug Interactions
- Anticoagulants — mild additive bleeding risk at high doses
- Oral medications — fibre in whole seed can delay absorption; separate by two hours
- Antihypertensives — additive blood pressure lowering
- Tamoxifen — theoretical lignan interaction
Pregnancy & Breastfeeding
Pregnancy: likely_safe
Breastfeeding: likely_safe
Dosage Guidelines
Dosage Used in Studies
1000-15000 mg
Best Time to Take
With meals
Best Form
Cold-pressed, dark bottle, refrigerated; or ground whole flaxseed for lignans and fibre
Bioavailability
ALA is well absorbed; the bottleneck is enzymatic conversion downstream, not absorption.
Forms Compared
Cold-pressed oil
Ground flaxseed
Whole flaxseed
Algal oil (alternative)
Food & Timing
With food. Never heat it — the polyunsaturated fatty acids oxidise readily.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.