NutriDex

The Supplement Research Compendium
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Flaxseed (ALA)

Linum usitatissimum

Fibre-rich seed that modestly trims cholesterol, blood pressure and glucose.

Moderate evidence 🫀Heart & Metabolic🛡️Gut & Immune

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
7 verified / 7
Classification
Heart & Metabolic
❝
What the evidence says. Graded moderate: dozens of RCTs and several meta-analyses show real but small reductions in LDL, blood pressure and fasting glucose, yet effects are modest, depend heavily on form (ground seed > oil > lignan), and HbA1c and inflammation results are mixed. (Moderate evidence: Several controlled trials; effects real but modest or context-dependent.)

What is Flaxseed (ALA)?

Flaxseed (ALA) (Linum usitatissimum) is a heart and metabolic supplement used for lower ldl & total cholesterol. NutriDex grades the human evidence as Moderate. Flaxseed is an oilseed rich in the plant omega-3 ALA, lignans and viscous fibre. Pooled trial data are consistent but modest: a 62-RCT meta-analysis found ground flaxseed lowered total cholesterol by ~5 mg/dL, LDL by ~4 mg/dL and triglycerides by ~9 mg/dL, with no change in HDL. Blood-pressure meta-analyses report drops of roughly 2–3 mmHg overall, though one landmark 6-month trial in hypertensive patients saw falls near 15/7 mmHg. For glucose, ground flaxseed cut fasting glucose (~3 mg/dL), insulin and HOMA-IR, especially over 12+ weeks, but most analyses found no HbA1c change (one found a small reduction in poorly-controlled diabetes). Effects are larger for milled whole seed than for oil or lignan extracts. CRP falls mainly in obese subjects. Practical, food-based and safe, but the magnitude is adjunctive, not a substitute for statins or antihypertensives.

Purported Benefits

✓Lower LDL & total cholesterol
✓Modest blood-pressure reduction
✓Better fasting glucose & insulin sensitivity
✓Relieve constipation (fibre)
✓Lower CRP in obesity

Evidence by outcome

The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.

OutcomeEvidenceEffectStudies
Lower LDL & total cholesterol62-RCT meta-analysis: small but consistent drops (TC -5, LDL -4 mg/dL); whole milled seed works best, no HDL change. Strong ↑ benefit · small 1
Lower blood pressure15-RCT meta-analysis shows ~2-3 mmHg drop; one 6-mo PAD trial saw larger ~15/7 mmHg falls in hypertensives. Moderate ↑ benefit · small 2
Improve fasting glucose & insulin sensitivity25-RCT meta-analysis: modest fasting glucose/HOMA-IR drops, significant only for whole seed used ≥12 weeks. Moderate ↑ benefit · small 2
Lower HbA1c in type 2 diabetes13-RCT diabetes meta-analysis found HbA1c reduction (esp. baseline ≥7%), but broader pooling saw no HbA1c change. Moderate ↔ mixed · small 2
Lower CRP / inflammationOne 54-RCT meta-analysis found CRP/IL-6 reductions; another found no overall CRP change except in obese subgroup. Mixed ↔ mixed · small 2

Dosing & Compounds

Typical Dose
Typically 30 g/day of milled (ground) whole flaxseed; benefits are strongest for ground seed taken ≥12 weeks, weaker for oil or isolated lignans.
Active Compounds
Alpha-linolenic acid (ALA, omega-3)Lignans (secoisolariciresinol diglucoside)Soluble & insoluble fibre (mucilage)

Safety & Cautions

Generally safe as a food; common effects are bloating, gas and loose stools from its fibre, and it can cause constipation or bowel obstruction if taken with too little water. Because ALA and fibre can mildly slow clotting and lower glucose, it may add to the effect of anticoagulants/antiplatelets (warfarin, aspirin, clopidogrel) and diabetes medications, and its fibre can blunt absorption of oral drugs taken at the same time (separate by ~1–2 hours). Raw or unripe seed contains trace cyanogenic glycosides, so stick to recommended amounts; avoid medicinal doses in pregnancy due to phytoestrogen/lignan content. Educational only — always check with your doctor or pharmacist before combining Flaxseed (ALA) with any medicine.

Flaxseed (ALA) drug interactions

Known or theoretical interactions between Flaxseed (ALA) and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Flaxseed (ALA) with any medicine.

Monitor
Blood thinners (warfarin, DOACs)
High-dose flaxseed or flaxseed oil may slightly add to bleeding risk alongside blood thinners.
ALA omega-3 content can mildly reduce platelet aggregation, modestly compounding anticoagulant effects. NCCIH — Flaxseed and Flaxseed Oil
Monitor
Antiplatelet drugs (aspirin, clopidogrel)
Flaxseed with aspirin or clopidogrel may modestly increase bleeding tendency at high doses.
ALA omega-3 can mildly reduce platelet aggregation, adding to antiplatelet effects. NCCIH — Flaxseed and Flaxseed Oil

Key Studies

Meta-analysis Xi 2023 ✓ PubMed
13 RCTs in type 2 diabetes: whole flaxseed significantly lowered HbA1c (most pronounced when baseline HbA1c ≥7%); no change in BP or weight.
Meta-analysis Musazadeh 2024 ✓ PubMed
GRADE-assessed 54-RCT meta-analysis (n=3000): flaxseed lowered CRP (SMD -0.46) and IL-6 (SMD -0.64); no change in TNF-α.
Meta-analysis Hadi 2020 ✓ PubMed
62-RCT dose-response meta-analysis (n=3772): flaxseed cut total cholesterol -5.4, LDL -4.2 and triglycerides -9.4 mg/dL; no HDL change.
Meta-analysis Ursoniu 2016 ✓ PubMed
15 RCTs (n=1302): flaxseed lowered systolic BP -2.85 and diastolic BP -2.39 mmHg; effect larger in trials lasting ≥12 weeks.
Meta-analysis Mohammadi-Sartang 2017 ✓ Full text
25 RCTs: flaxseed reduced fasting glucose -2.94 mg/dL, insulin -7.32 pmol/L and HOMA-IR -0.49; significant only for whole seed ≥12 weeks.
Meta-analysis Ren 2016 ✓ PubMed
Meta-analysis: flaxseed did NOT change CRP overall (-0.13 mg/L, p=0.43); significant reduction only in obese subgroup (BMI ≥30).
RCT Rodriguez-Leyva 2013 ✓ PubMed
RCT, 110 PAD patients, 30 g/day milled flax for 6 mo: systolic BP fell ~15 mmHg and diastolic ~7 mmHg vs placebo in hypertensives.
7 sources cited · 7 verified Search all studies on PubMed ↗

Common questions about Flaxseed (ALA)

What is Flaxseed (ALA) used for?

Flaxseed (ALA) is most often taken for Lower LDL & total cholesterol, Modest blood-pressure reduction, Better fasting glucose & insulin sensitivity, Relieve constipation (fibre). Fibre-rich seed that modestly trims cholesterol, blood pressure and glucose.

Does Flaxseed (ALA) work — what does the evidence say?

Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Flaxseed is an oilseed rich in the plant omega-3 ALA, lignans and viscous fibre. Pooled trial data are consistent but modest: a 62-RCT meta-analysis found ground flaxseed lowered total cholesterol by ~5 mg/dL, LDL by ~4 mg/dL and triglycerides by ~9 mg/dL, with no change in HDL. Blood-pressure meta-analyses report drops of roughly 2–3 mmHg overall, though one landmark 6-month trial in hypertensive patients saw falls near 15/7 mmHg. For glucose, ground flaxseed cut fasting glucose (~3 mg/dL), insulin and HOMA-IR, especially over 12+ weeks, but most analyses found no HbA1c change (one found a small reduction in poorly-controlled diabetes). Effects are larger for milled whole seed than for oil or lignan extracts. CRP falls mainly in obese subjects. Practical, food-based and safe, but the magnitude is adjunctive, not a substitute for statins or antihypertensives.

What is the typical dose of Flaxseed (ALA)?

Typically 30 g/day of milled (ground) whole flaxseed; benefits are strongest for ground seed taken ≥12 weeks, weaker for oil or isolated lignans.

Is Flaxseed (ALA) safe? Any cautions or side effects?

Generally safe as a food; common effects are bloating, gas and loose stools from its fibre, and it can cause constipation or bowel obstruction if taken with too little water. Because ALA and fibre can mildly slow clotting and lower glucose, it may add to the effect of anticoagulants/antiplatelets (warfarin, aspirin, clopidogrel) and diabetes medications, and its fibre can blunt absorption of oral drugs taken at the same time (separate by ~1–2 hours). Raw or unripe seed contains trace cyanogenic glycosides, so stick to recommended amounts; avoid medicinal doses in pregnancy due to phytoestrogen/lignan content.

How many studies support Flaxseed (ALA)?

NutriDex cites 7 sources for Flaxseed (ALA), graded "Moderate".

Does Flaxseed (ALA) interact with any medications?

Yes — known or theoretical interactions include: Blood thinners (warfarin, DOACs) (monitor), Antiplatelet drugs (aspirin, clopidogrel) (monitor). This is educational and not exhaustive; always check with your doctor or pharmacist before combining Flaxseed (ALA) with any medicine.

Cite this page
APA

Peh, D. (2026). Flaxseed (ALA) (Linum usitatissimum): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/flaxseed

BibTeX
@misc{nutridex_flaxseed,
  author       = {Peh, Daryl},
  title        = {Flaxseed (ALA) (Linum usitatissimum): Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/flaxseed},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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