Flaxseed
Linum usitatissimum
Small seeds rich in fiber and the omega-3 fat ALA, eaten whole, ground or as oil. Research suggests flaxseed may lower blood pressure and cholesterol slightly.
Safety at a glance
- Pregnancy1 note →
- BreastfeedingNothing recorded
- Medicines1 note →
- Who should avoid it1 note →
- AllergiesNothing recorded
- Toxicity1 note →
Tap a box to read the safety notes below. “Nothing recorded” means our sources don't cover it, not that it's safe.
Flaxseed may interact with some medicines. If you take any medicine, read Interactions with medicines below and talk to your doctor or pharmacist before using it.
What is Flaxseed?
- Plant family
- Linaceae, the flax family
- Parts used
- The seeds, eaten whole or ground, or pressed to make flaxseed (linseed) oil
- Genus
- Linum
- Species
- usitatissimum
Also called
Flax, Linseed
Traditionally used for
- Food
- Constipation
- Blood pressure
- Cholesterol
Traditionally described as
- Gentle laxative
- May lower cholesterol slightly
Health topics
Where Flaxseed appears in symptom search, and why. Being listed doesn't mean it's a proven treatment.
- High Blood Pressure
A review of trials found flaxseed lowered blood pressure slightly, especially whole seeds eaten for 12 weeks or more.
- High Cholesterol
Whole flaxseed and lignan supplements lowered total and LDL cholesterol slightly; flaxseed oil didn't.
- Menopausal Weight Gain
Trials in adults found small drops in weight and waist size. It hasn't been tested specifically for weight gain in menopause.
Traditions that use it
- Mediterranean Folk Medicine
Used as a laxative in ancient Greece, and to make linen in ancient Egypt.
- European Folk Medicine
Recognized by the European Medicines Agency for constipation and, based on long-standing use, for mild stomach and gut discomfort.
Natural compounds
How it's prepared
Common ways Flaxseed is prepared or sold. This isn't advice on how to take it; see Safety below.
- Oil
Flaxseed oil is sold as a supplement.[1]Health agency
- Poultice
North American settlers used flaxseed in poultices (a paste put on the skin).[1]Health agency
Safety
Interactions with medicines
In theory, flaxseed could interact with blood thinners and anti-platelet medicines. Talk to your health care provider before using it.[1]Health agency
Who should avoid it
Don't use linseed if you have trouble swallowing or throat problems, a blocked or narrowed gut, a paralyzed or abnormally widened bowel, or a disease of the esophagus (food pipe). For constipation, don't use it if you've had a sudden change in bowel habits lasting more than 2 weeks, unexplained bleeding from the bottom, or constipation that laxatives haven't relieved. It's for adults and teens over 12 only.[2]Health agency
Side effects
Higher doses can cause bloating, fullness and diarrhea.[1]Health agency
Bloating is a common side effect (1 to 10 in 100 people). Very rarely, allergic reactions, sometimes severe, have been reported.[2]Health agency
Pregnancy
The evidence on flaxseed's safety during pregnancy isn't conclusive, and little is known about its safety while breastfeeding.[1]Health agency
Toxicity testing
Don't eat raw or unripe flaxseeds; they may contain potentially toxic compounds.[1]Health agency
What does the research say?
Traditional use
These are traditional uses, not proven treatments.
Flaxseed has a long history of use: to make linen in ancient Egypt, in stews in Ethiopia and as a laxative in ancient Greece. North American settlers used it in poultices (a paste put on the skin) and in paint oil. Today it's promoted for the heart, brain and immune system.[1]Health agency
Based on long-standing use, the European Medicines Agency recognizes linseed for relieving mild stomach and gut discomfort.[2]Health agency
Research in people
Based on clinical studies, the European Medicines Agency concluded that linseed can treat long-term (habitual) constipation or soften stools. Linseed swells with water in the gut to form a jelly-like substance that softens the stool and helps it pass.[2]Health agency
Technical detail: "well-established use"; the jelly-like substance is mucilage.
One trial suggests flaxseed fiber (mucilage) powder mixed with water might help overweight adults lose weight, but lignan extracts and oil supplements didn't help. Flaxseed oil might improve blood sugar measures in pregnant people with gestational diabetes. It's unclear whether flaxseed helps type 2 diabetes.[1]Health agency
A 2015 review of 14 trials found flaxseed lowered blood pressure slightly: by about 1.8 mm Hg (systolic, the top number) and 1.6 mm Hg (diastolic, the bottom number). The effect on diastolic pressure may be larger with whole flaxseed eaten for 12 weeks or more.[3]Review or trial
Technical detail: 11 studies (14 trials); SBP −1.77 mm Hg (95% CI −3.45 to −0.09); DBP −1.58 mm Hg (95% CI −2.64 to −0.52); whole seed DBP −1.93 mm Hg; ≥12 weeks DBP −2.17 mm Hg.
A 2009 review of 28 studies found flaxseed lowered total and LDL ("bad") cholesterol slightly. Whole flaxseed and lignan supplements worked, but flaxseed oil didn't. The effect was clearer in women (especially after menopause) and in people who started with high cholesterol. It didn't change HDL ("good") cholesterol or triglycerides.[4]Review or trial
Technical detail: overall total cholesterol −0.10 mmol/L and LDL −0.08 mmol/L; whole flaxseed −0.21 and −0.16 mmol/L; lignans −0.28 and −0.16 mmol/L.
A 2024 review that pooled 64 trials found flaxseed supplements led to small drops in body weight (about 0.6 kg, or 1.4 lb), BMI and waist size (about 1.4 cm). Effects were larger in people with obesity and in trials lasting 10 to 20 weeks.[5]Review or trial
In short
Don't eat raw or unripe seeds; not for people with swallowing problems or a blocked gut.
Sources
- [1] Flaxseed and Flaxseed Oil: Usefulness and Safety — National Center for Complementary and Integrative Health (NIH)Government health agency
- [2] Linseed: Herbal medicine summary for the public (EMA/492394/2015) — European Medicines Agency, Committee on Herbal Medicinal Products (HMPC)Government health agency
- [3] Flaxseed consumption may reduce blood pressure: a systematic review and meta-analysis of controlled trials — The Journal of Nutrition · DOI: 10.3945/jn.114.205302Review or clinical trial
- [4] Meta-analysis of the effects of flaxseed interventions on blood lipids — The American Journal of Clinical Nutrition · DOI: 10.3945/ajcn.2009.27469Review or clinical trial
- [5] The effects of flaxseed (Linum usitatissimum) supplementation on anthropometric indices: An updated systematic review and meta-analysis of randomized clinical trials · DOI: 10.1016/j.ctim.2024.103066Review or clinical trial
This information is educational and traditional in nature, and is not a substitute for professional medical advice. Unfamiliar word? See what these words mean.