Is flaxseed oil good for heart health?

Nobody has run a trial of flaxseed oil that counts heart attacks, strokes or deaths, so the honest answer is that we do not know. The closest evidence is about ALA, the plant omega-3 that makes up most of the oil. A 2020 Cochrane review of 5 trials in 19,327 people found that eating more ALA probably makes little or no difference to death from any cause, or to cardiovascular death (risk ratio 0.96, 95% CI 0.74 to 1.25, 4 trials, 18,619 people). The ALA in those trials came from enriched margarine, oils or advice, not from flaxseed oil bottles.

Unsettled. The one possible benefit is small and rests on two trials. In the same Cochrane review, more ALA probably slightly lowered the risk of arrhythmia (RR 0.73, 95% CI 0.55 to 0.97, 4,912 people, 173 events). That works out to one fewer case for every 91 people. For all cardiovascular events the estimate was RR 0.95 with an interval from 0.83 to 1.07, which includes no effect, on low-certainty evidence.

More plant omega-3 (ALA) and the heart, risk ratios

Randomized trialsObservational data

None of these trials gave flaxseed oil itself. ALA came from enriched margarine, oils or dietary advice, and the cohort row is observational, so it cannot show cause. A bar crossing 1.0 means no clear difference. Sources: cards ev-flxoh-01, ev-flxoh-02, ev-flxoh-04 and ev-flxoh-13 below.

What the trials found

Heart attacks and deaths: tested for ALA, not for the oil

The biggest single trial is Alpha Omega. It gave 4,837 heart attack survivors aged 60 to 80 a margarine with about 2 g of extra ALA a day for 40 months. Major cardiovascular events did not fall significantly (hazard ratio 0.91, 95% CI 0.78 to 1.05). The Cochrane reviewers also found that more ALA had little or no effect on serious adverse events, blood lipids or blood pressure.

Observational data point the other way, gently. Across cohort studies of about 1.2 million people, each extra 1 g of ALA a day was linked with a 5% lower risk of cardiovascular death (0.95, 95% CI 0.91 to 0.98). The authors give a tablespoon of canola oil as an example of 1 g. That is an association in people eating ALA mostly from mixed foods, and the randomized trials above did not confirm it.

Blood pressure: depends on who was tested

A 2022 meta-analysis of 5 trials in people with metabolic syndrome and related disorders found flaxseed oil lowered systolic blood pressure by 3.86 mmHg. Its confidence interval ran from 7.59 down to 0.13 mmHg, so the lower end sits close to zero. In healthy or at-risk adults, a 2024 meta-analysis of 17 trials of olive or flaxseed oil found no effect on systolic pressure (-0.48 mmHg, 95% CI -1.76 to 0.80). Only 3 of those 17 trials used flaxseed oil.

The best-measured single trial was also negative. In a double-blind trial of 59 overweight adults with high-normal or stage 1 hypertension, 10 g of flaxseed oil a day for 12 weeks changed 24-hour systolic pressure by -1.5 mmHg against high-oleic sunflower oil (95% CI -6.0 to 3.0), which was not significant. The same trial found no change in artery dilation, arterial stiffness or the small vessels of the retina.

A 2023 meta-analysis of 19 trials in 1,183 adults with overweight or obesity found plant ALA from several sources lowered triglycerides and systolic pressure and raised LDL cholesterol. The abstract reports these as standardized differences, so their size in everyday units is unclear. In the full text, the systolic drop showed up only in trials lasting 12 weeks or more, using flaxseed or its products, giving at least 3 g of ALA, or enrolling people with high blood pressure. Subgroups like these are exploratory.

Cholesterol: the oil and the seed are different foods

In an Iranian trial of 60 adults with metabolic syndrome, 1.7 tbsp (25 mL) of flaxseed oil a day for 7 weeks did not improve blood lipids or blood sugar more than sunflower oil. A 2020 meta-analysis of 62 trials with 3,772 people did find flaxseed products lowered LDL by about 4 mg/dL and triglycerides by about 9 mg/dL. Most of those trials used ground seed, which carries fiber and lignans the oil lacks, so that result may not transfer to the bottle.

Myth. The idea that flaxseed oil is a proven heart food does not survive the trials. The EU looked at the label claim that flaxseed oil or its ALA promotes heart health and did not authorize it. That means the evidence did not meet the bar, which is weaker than proof of no effect.

Who should be careful

Not for everyone. The NIH center for complementary health says higher doses of flaxseed or flaxseed oil supplements may cause bloating, fullness and diarrhea. It also notes theoretical reasons the oil might interact with anticoagulant or antiplatelet drugs. That interaction has not been shown in a trial, and we found no study of it, so if you take a blood thinner, raise the oil with whoever prescribes it. The same center says little is known about whether flaxseed oil is safe during pregnancy or breastfeeding.

On the reassuring side, the Cochrane review found that more ALA had little or no effect on serious adverse events. The ALA in those trials came mostly through food, so they say little about high-dose oil capsules.

What expert bodies say

The EU did not authorize the claim that flaxseed oil or alpha-linolenic acid promotes heart health. We found no position from a heart association or food safety body on flaxseed oil specifically. The NIH center for complementary health is cited on this page for safety only.

How we searched

Searched: a local copy of the PubMed baseline across all study types, with three queries combining flaxseed, linseed and alpha-linolenic acid with cardiovascular, blood pressure, cholesterol and coronary terms, and with bleeding and drug interaction terms. The broadest returned 684 records, many of them about alpha-lipoic acid, a different substance that shares the abbreviation ALA. The query for flaxseed oil itself returned 221 records with no meta-analysis of hard heart outcomes. We also searched our drug interaction, breastfeeding and EU health claims layers and ClinicalTrials.gov, and ran three web searches for newer meta-analyses and agency safety pages. Search run on 7 October 2026.

Included: 12 sources on 17 cards: the Cochrane review, the Alpha Omega trial, four meta-analyses of trials, three reports from two randomized trials, one meta-analysis of cohort studies, the NIH complementary health fact sheet and the EU claims register. None of the studies we checked is listed in the Retraction Watch database.

Excluded: a meta-analysis of whole flaxseed and blood pressure with no oil-specific estimate, a narrative review labeled as a meta-analysis, a 2006 review superseded by the Cochrane review, a trial in kidney disease only, and every alpha-lipoic acid study.

What we read: abstracts from the PubMed baseline, and the results section of the 2023 meta-analysis in full text for its subgroups. The NIH fact sheet was checked by two independent requests.

What we could not get: the NIH Office of Dietary Supplements omega-3 fact sheet, which refused automated access, and the full texts of the 2022 flaxseed oil and 2020 flaxseed lipid meta-analyses. We did not use the authorized EU claim on ALA and cholesterol, because its condition of use sits in a regulation we did not fetch.

What would change this answer

A randomized trial of flaxseed oil itself that counts heart attacks, strokes or deaths. None exists, so every hard-outcome answer on this page is borrowed from ALA delivered another way.
Results from the registered trial of flax oil capsules and blood pressure (NCT04759508). Its status is unknown and it has posted no results.
A larger, longer blood pressure trial in people with high blood pressure, since that is the group where the subgroup analysis suggests any effect would show.

For what flaxseed oil contains and how it fits a diet, see the flaxseed oil page.

The food behind this question

Flaxseed oil: a small blood pressure drop, seen in people who were already unwell — numbers, evidence and safety

The same question for other foods (heart health)

Sources

ev-flxoh-01 · Meta-analysis or systematic review · Cochrane systematic review and random-effects meta-analysis of RCTs · n = 19327
Increasing ALA intake probably makes little or no difference to all-cause mortality (RR 1.01, 95% CI 0.84 to 1.20; 19,327 participants; 459 deaths in 5 RCTs, moderate-certainty evidence),cardiovascular mortality (RR 0.96, 95% CI 0.74 to 1.25; 18,619 participants; 219 cardiovascular deaths in 4 RCTs; moderate-certainty evidence), coronary heart disease mortality (RR 0.95, 95% CI 0.72 to 1.26; 18,353 participants; 193 coronary heart disease deaths in 3 RCTs; moderate-certainty evidence) and coronary heart disease events (RR 1.00, 95% CI 0.82 to 1.22; 19,061 participants; 397 coronary heart disease events in 4 RCTs; low-certainty evidence).
Who: adults at varying cardiovascular risk in RCTs of at least 12 months increasing ALA intake
Effect: all-cause mortality RR 1.01 (95% CI 0.84 to 1.20); cardiovascular mortality RR 0.96 (95% CI 0.74 to 1.25), 4 RCTs, 18,619 people; moderate certainty
Certainty: ALA came from enriched margarine, oils or advice, not flaxseed oil specifically; GRADE moderate to low.
Cochrane Database Syst Rev, 2020 · checked 2026-10-07 · we read the abstract
ev-flxoh-02 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = 4912
However, increased ALA may slightly reduce risk of cardiovascular disease events (NNTB 500, RR 0.95, 95% CI 0.83 to 1.07; but RR 0.91, 95% CI 0.79 to 1.04 in RCTs at low summary risk of bias; 19,327 participants; 884 cardiovascular disease events in 5 RCTs; low-certainty evidence), and probably slightly reduces risk of arrhythmia (NNTB 91, RR 0.73, 95% CI 0.55 to 0.97; 4912 participants; 173 events in 2 RCTs; moderate-certainty evidence).
Who: participants in 2 RCTs of increased ALA reporting arrhythmia
Effect: arrhythmia RR 0.73 (95% CI 0.55 to 0.97), NNTB 91; CVD events RR 0.95 (0.83 to 1.07), NNTB 500
Certainty: Only 2 trials and 173 events; moderate certainty.
Cochrane Database Syst Rev, 2020 · checked 2026-10-07 · we read the abstract
ev-flxoh-03 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = —
Increasing LCn3 and ALA had little or no effect on serious adverse events, adiposity, lipids and blood pressure, except increasing LCn3 reduced triglycerides by ˜15% in a dose-dependent way (high-certainty evidence).
Who: adults in RCTs of at least 12 months increasing ALA or long-chain omega-3
Effect: little or no effect on serious adverse events, adiposity, lipids and blood pressure for ALA
Certainty: Covers ALA from all sources; lipid and BP results are secondary outcomes.
Cochrane Database Syst Rev, 2020 · checked 2026-10-07 · we read the abstract
ev-flxoh-04 · Randomized controlled trial(s) · multicentre double-blind placebo-controlled factorial RCT · n = 4837
Neither EPA-DHA nor ALA reduced this primary end point (hazard ratio with EPA-DHA, 1.01; 95% confidence interval [CI], 0.87 to 1.17; P=0.93; hazard ratio with ALA, 0.91; 95% CI, 0.78 to 1.05; P=0.20).
Who: patients aged 60 through 80 after myocardial infarction on standard drug therapy, 78% men; margarine with 2 g/day ALA, EPA-DHA, both, or placebo for 40 months
Effect: major cardiovascular events HR 0.91 (95% CI 0.78 to 1.05) for ALA; women subgroup HR 0.73 (0.51 to 1.03)
Certainty: ALA from enriched margarine, not flaxseed oil; women subgroup result is borderline.
N Engl J Med, 2010 · checked 2026-10-07 · we read the abstract
ev-flxoh-05 · Meta-analysis or systematic review · systematic review and random-effects meta-analysis of RCTs · n = 5 trials (6 arms)
Meta-analysis of five trials (6 arms) showed significant reductions in systolic (WMD: -3.86 mmHg, 95% CI: -7.59 to -0.13, p = .04) BP (SBP) after flaxseed oil consumption.
Who: patients with metabolic syndrome and related disorders in RCTs of flaxseed oil
Effect: systolic BP WMD -3.86 mmHg (95% CI -7.59 to -0.13)
Certainty: Few small trials; upper confidence limit close to zero; search to March 2020.
Phytother Res, 2022 · checked 2026-10-07 · we read the abstract
ev-flxoh-06 · Meta-analysis or systematic review · systematic review and random-effects meta-analysis of RCTs · n = 17 RCTs
Meta-analysis using a random-effects model reported no significant effect on SBP n=17 mean difference (MD) -0.48; 95% CI: -1.76, 0.80; p=0.65, I2 =0%) and DBP (n=16, MD -0.47; 95% CI: -1.33, 0.39; p=0.65, I2 =0%) or inflammatory markers, CRP (n=8, MD 0.11; 95% CI: -1.18, 0.40; p=0.98, I2 =0%), IL6 (n=3, MD -0.15; 95% CI: -0.57, 0.27; p=0.87, I2 =0%), and TNFα (n=3, MD-0.08; 95% CI: -0.12, -0.03; p=0.98, I2 =0%).
Who: normotensive adults or adults at risk of hypertension; 14 olive oil and 3 flaxseed oil RCTs
Effect: systolic BP MD -0.48 mmHg (95% CI -1.76 to 0.80); diastolic BP -0.47 mmHg (-1.33 to 0.39); CRP, IL-6 not changed
Certainty: Only 3 of 17 trials used flaxseed oil; no separate flaxseed oil estimate in the abstract.
Curr Hypertens Rev, 2024 · checked 2026-10-07 · we read the abstract
ev-flxoh-07 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 1183
Compared with placebo, dietary ALA supplementation significantly reduced C-reactive protein concentration (standardized mean difference [SMD] = -0.38 mg/L; 95% confidence interval [CI]: -0.72, -0.04), tumor necrosis factor-α concentration (SMD = -0.45 pg/mL; 95% CI: -0.73, -0.17), triglyceride in serum (SMD = -4.41 mg/dL; 95% CI: -5.99, -2.82), and systolic blood pressure (SMD = -0.37 mm Hg; 95% CI: -0.66, -0.08); but led to a significant increase in low-density lipoprotein cholesterol concentrations (SMD = 1.32 mg/dL; 95% CI: 0.05, 2.59).
Who: adults with overweight or obesity; ALA from flaxseed, flaxseed oil, walnuts, chia and other plant sources vs placebo
Effect: triglycerides SMD -4.41 (95% CI -5.99 to -2.82); systolic BP SMD -0.37 (-0.66 to -0.08); LDL SMD +1.32 (0.05 to 2.59); no effect on total cholesterol, HDL or diastolic BP
Certainty: Results reported as standardized mean differences with mg/dL labels; high heterogeneity; ALA sources mixed.
Adv Nutr, 2023 · checked 2026-10-07 · we read the abstract
ev-flxoh-08 · Meta-analysis or systematic review · subgroup analysis within a meta-analysis of RCTs · n = 10 studies
In the subgroup analysis, the significant effects were only observed in studies with longer duration (≥12 wk), used flaxseed and its derivatives as ALA source, or used higher doses of ALA (≥3 g), included participants with higher baseline BMI (≥30 kg/m2), included participant with hypertension at baseline (SBP ≥ 130 or DBP ≥ 80 mm Hg), or studies of fair quality (Supplementary Table 4).
Who: 10 RCTs reporting systolic BP in adults with overweight or obesity
Effect: systolic BP SMD -0.37 (95% CI -0.66 to -0.08), I2 71.58%; significant only in subgroups listed
Certainty: Subgroup findings across trials are observational and exploratory.
Adv Nutr, 2023 · checked 2026-10-07 · we read the fulltext
ev-flxoh-09 · Randomized controlled trial(s) · double-blind randomized placebo-controlled parallel trial · n = 59
Compared with control, the changes of -1·4 mmHg in mean arterial pressure (MAP; 24 h ABP) after flaxseed oil intake (95 % CI -4·8, 2·0 mmHg, P=0·40) of -1·5 mmHg in systolic BP (95 % CI -6·0, 3·0 mmHg, P=0·51) and of -1·4 mmHg in diastolic BP (95 % CI -4·2, 1·4 mmHg, P=0·31) were not statistically significant.
Who: overweight and obese adults with (pre-)hypertension, mean age 60; 10 g/day flaxseed oil (4.7 g ALA) vs high-oleic sunflower oil, 12 weeks
Effect: 24-h systolic BP -1.5 mmHg (95% CI -6.0 to 3.0); diastolic -1.4 mmHg (-4.2 to 1.4); mean arterial pressure -1.4 mmHg (-4.8 to 2.0)
Certainty: Small; ambulatory BP is a strong measure; dose was 3 to 5 times recommended ALA intake.
Br J Nutr, 2019 · checked 2026-10-07 · we read the abstract
ev-flxoh-10 · Randomized controlled trial(s) · double-blind randomized placebo-controlled parallel trial · n = 59
As compared with the high-oleic oil control, intake of flaxseed oil did not change brachial artery flow-mediated vasodilation, carotid-to-femoral pulse wave velocity, retinal microvascular calibers and plasma markers of microvascular endothelial function during the fasting and postprandial phase.
Who: overweight and obese adults with high-normal BP or stage 1 hypertension; 10 g/day flaxseed oil (4.7 g ALA) vs high-oleic sunflower oil, 12 weeks
Effect: no change in flow-mediated vasodilation, pulse wave velocity, retinal microvascular calibers; fasting free fatty acids -58 µmol/L and TNF-α -0.14 pg/mL
Certainty: Same trial as ev-flxoh-09; surrogate vascular outcomes.
Clin Nutr, 2020 · checked 2026-10-07 · we read the abstract
ev-flxoh-11 · Randomized controlled trial(s) · randomized controlled trial · n = 60
The results showed no significant difference between the 2 groups regarding blood lipid levels and fasting blood sugar at the end of the study.
Who: adults aged 30 to 60 with metabolic syndrome in Shiraz, Iran; 25 mL/day flaxseed oil vs 25 mL/day sunflower oil, 7 weeks
Effect: no between-group difference in blood lipids or fasting blood sugar at 7 weeks
Certainty: Not blinded per abstract; short; BP drop much larger than in other trials.
J Clin Lipidol, 2018 · checked 2026-10-07 · we read the abstract
ev-flxoh-12 · Meta-analysis or systematic review · systematic review and dose-response meta-analysis of RCTs · n = 3772
Our analysis showed that flaxseed supplementation significantly reduced total cholesterol (TC) (WMD = -5.389 mg/dL; 95% CI: -9.483, -1.295, p = 0.010), triglyceride (TG) (WMD = -9.422 mg/dL; 95% CI: -15.514, -3.330, p = 0.002), and low-density lipoprotein cholesterol (LDL-C) (WMD = -4.206 mg/dl; 95% CI: -7.260, -1.151, p = 0.007) concentrations.
Who: participants in 62 RCTs of flaxseed supplementation in any form
Effect: LDL WMD -4.21 mg/dL (95% CI -7.26 to -1.15); total cholesterol -5.39 mg/dL; triglycerides -9.42 mg/dL; HDL no change
Certainty: Whole flaxseed contains fiber and lignans that oil lacks, so this result may not transfer to flaxseed oil.
Pharmacol Res, 2020 · checked 2026-10-07 · we read the abstract
ev-flxoh-13 · Observational data · systematic review and dose-response meta-analysis of prospective cohorts · n = 1197564
In the dose-response analysis, a 1 g/day increase in ALA intake (equivalent to one tablespoon of canola oil or 0.5 ounces of walnut) was associated with a 5% lower risk of all cause (0.95, 0.91 to 0.99, I2=76.2%, n=12) and CVD mortality (0.95, 0.91 to 0.98, I2=30.7%, n=14).
Who: prospective cohort studies, follow-up 2 to 32 years
Effect: per 1 g/day ALA: CVD mortality RR 0.95 (95% CI 0.91 to 0.98), 14 analyses; all-cause mortality 0.95 (0.91 to 0.99), 12 analyses
Certainty: Observational; residual confounding possible; ALA mostly from mixed foods, not flaxseed oil.
BMJ, 2021 · checked 2026-10-07 · we read the abstract
ev-flxoh-14 · Position of an expert body · agency consumer fact sheet · n = —
Higher doses of flaxseed or flaxseed oil supplements may cause uncomfortable digestive symptoms like bloating, fullness, and diarrhea.
Who: adults using flaxseed or flaxseed oil supplements
Effect: digestive symptoms at higher doses; theoretical interaction with anticoagulant or antiplatelet drugs
Certainty: Interaction is theoretical; NCCIH advises talking to a provider when taking medicines.
NIH National Center for Complementary and Integrative Health, Flaxseed and Flaxseed Oil, last updated February 2025 · checked 2026-10-07 · we read the section
ev-flxoh-15 · Position of an expert body · agency consumer fact sheet · n = —
There are theoretical reasons to suspect that flaxseed or flaxseed oil might interact with other drugs, such as anticoagulant or antiplatelet drugs.
Who: people taking anticoagulant or antiplatelet medicines
Effect: possible interaction, not demonstrated
Certainty: Theoretical; corpus holds only one case report without abstract (23795184), not used.
NIH National Center for Complementary and Integrative Health, Flaxseed and Flaxseed Oil, last updated February 2025 · checked 2026-10-07 · we read the section
ev-flxoh-16 · Position of an expert body · agency consumer fact sheet · n = —
Little is known about whether it is safe to use flaxseed oil during pregnancy or while breastfeeding.
Who: pregnant and breastfeeding women
Effect: safety unknown
Certainty: No T1 trial of flaxseed oil safety in pregnancy found in corpus.
NIH National Center for Complementary and Integrative Health, Flaxseed and Flaxseed Oil, last updated February 2025 · checked 2026-10-07 · we read the section
ev-flxoh-17 · Position of an expert body · EU register entry · n = —
POL-HC-7106 Flaxseed oil/alpha-linoleic acid Promotes heart health Non-authorised
Who: EU food labeling
Effect: claim non-authorized
Certainty: Non-authorized means evidence did not meet the bar at assessment, not proof of no effect.
EU Register on nutrition and health claims, claim POL-HC-7106, snapshot 2026-09-21 · checked 2026-10-07 · we read the section

How this page was made. Evidence was extracted from primary sources into cards, every number was re-checked against the source, and the text was written from those cards. Bioma Learn has no human medical reviewer at this time, and we say so rather than invent one. Methodology. This is information, not medical advice.

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Flaxseed oil or olive oil: different fats, no blood pressure effect — food page