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Western herbalism

FlaxseedLinum usitatissimum

Mucilage-rich seed. In a 90-person trial 50 g a day of flaxseed flour raised weekly bowel movements from 2 to 7, against 2 to 6 on lactulose.

Botanical name
Linum usitatissimum
Part used
seed
Also called
Linseed, Flax, Lini semen (pharmacopoeia name)
Used in
Western herbalism
Taken for
Constipation, The gut lining
Sold as
powder, capsules, fresh

What flaxseed is

Flaxseed, also called linseed, is the small brown or golden seed of the flax plant, Linum usitatissimum, the same plant that gives linen fiber. Its outer layer holds mucilage, a gum that swells into a gel in water, and the seed also holds fat, protein and fiber. The EMA monograph on linseed describes seeds containing nearly 25 percent bulk materials, made up of 3 to 6 percent mucilage and 4 to 7 percent dietary fibers.

Whole seeds, cracked or ground seeds, flour and seed oil are all sold. The oil carries almost none of the fiber, so trials of the seed cannot be read onto the oil. The EMA monograph notes that broken seeds act faster than whole seeds, which are slow to swell; it lists soaked seeds as a mucilaginous preparation for mild digestive discomfort and whole or broken seeds as a bulk laxative.

In supplements it appears as ground seed, capsules and powders, often in cleanse and fiber blends, and as a pantry food added to cereal or baking.

What the traditions use it for

Western herbalism

Goyal and colleagues, in a review of flax as an ancient medicine, report that Hippocrates advocated flax to relieve abdominal pain and that flax preparations were widely used in medicine as an enveloping, wound-healing agent in gastrointestinal disorders. The EU herbal committee (HMPC) accepted linseed for habitual constipation as a well-established use and, as a traditional use, as a demulcent (soothing, coating) preparation for the symptomatic relief of mild gastrointestinal discomfort. The Ayurvedic description of flax in the same review concerns the skin more than digestion, so we do not give an Ayurvedic gut use.

The constituents

The seed holds mucilage and fiber, which are what act in the gut, plus alpha-linolenic acid in the oil and lignans. The EMA monograph reports that the laxative effect is attributed to the bulk materials, especially mucilage, which binds water and swells into a lubricating gel in the intestine, and that part of the fiber is fermented in the colon, producing short-chain fatty acids and sometimes gas. It also reports that linseed contains 20 to 50 mg cyanide per 100 g as cyanogenic glycosides. In mouse and isolated-tissue experiments, Palla and Gilani found flaxseed oil and mucilage had laxative activity and the oil had antidiarrheal activity. These are animal findings.

The human evidence

Sun and colleagues randomized 90 adults with Rome IV functional constipation to 50 g a day of flaxseed flour (60 people) or 15 ml a day of lactulose (30 people) for 4 weeks. The median Wexner constipation score fell from 14 to 6.5 on flaxseed and from 15 to 9 on lactulose, and bowel movements per week rose from 2 to 7 on flaxseed and from 2 to 6 on lactulose. There was no placebo group, so part of the change may reflect the trial setting.

Soltanian and colleagues reported two analyses from one registered trial program in constipated people with type 2 diabetes. In 53 people, 10 g of flaxseed in cookies twice daily for 12 weeks changed the constipation symptom score by 2.46 against 0.41 on placebo cookies, and in the three-arm version with 77 people both flaxseed and psyllium (10 g twice daily) improved constipation symptoms and stool consistency more than placebo, with the authors rating flaxseed superior. Both are single-blind and come from one group in a specific population.

In an open pilot of 40 people with irritable bowel syndrome, Cockerell and colleagues gave two tablespoons of whole or ground linseed daily for 4 weeks. Improvement in symptom severity did not reach significance against no linseed (P=0.12 for whole, P=0.10 for ground), and stool frequency and consistency did not change significantly.

Still missing: a large placebo-controlled trial of flaxseed for constipation in the general population, and any trial of it for diarrhea.

StudyDoseWhat it found
Randomized trial, 90 adults with Rome IV functional constipation: flaxseed flour (n=60) vs lactulose (n=30) PMID 3222944350 g flaxseed flour a day vs 15 ml lactulose, 4 weeksWexner score 14 to 6.5 vs 15 to 9; bowel movements per week 2 to 7 vs 2 to 6
Single-blind randomized trial, 53 constipated people with type 2 diabetes: flaxseed cookies vs placebo cookies PMID 2976076110 g flaxseed twice daily for 12 weeksConstipation symptom score changed by 2.46 vs 0.41; weight 3.8 kg lower (placebo 0.0); LDL cholesterol 21.0 vs 4.3 mg/dl lower
Single-blind randomized trial, 77 constipated people with type 2 diabetes: flaxseed, psyllium or placebo cookies PMID 3066169910 g twice daily for 12 weeksBoth better than placebo for constipation symptoms and stool consistency; authors rated flaxseed superior
Open pilot randomized trial, 40 people with IBS: whole linseed, ground linseed, or none PMID 22690855Two tablespoons daily for 4 weeksSymptom severity improvement not significant vs none (P=0.12 whole, P=0.10 ground); no change in stool frequency or consistency

Doses, in trials and in practice

The EMA monograph for linseed lists, for adults and adolescents over 12, 10 to 15 g of seeds taken with 150 ml of water, milk or juice two to three times a day for constipation, with the effect starting 12 to 24 hours later; and, as a soothing preparation, 5 to 10 g of seeds soaked in 250 ml of water and taken half an hour before eating up to three times a day. It says to consult a practitioner if constipation does not resolve within 3 days. Trials used 50 g a day of flour (4 weeks), 10 g twice daily in cookies (12 weeks) and two tablespoons a day (4 weeks).

The amounts above are what trials and pharmacopoeias record, not a dose for you; your medicines and conditions change the answer, and a clinician or pharmacist who knows them is the person to ask.

What is known about safety

The EMA monograph lists meteorism (gas and bloating) as common with linseed and hypersensitivity, including anaphylaxis-like reactions, as very rare. It carries the same obstruction warnings as other bulk fibers: take each dose with at least 150 ml of fluid, because swelling in the throat or esophagus can cause choking and intestinal obstruction. Contraindications include a sudden change in bowel habit lasting more than 2 weeks, undiagnosed rectal bleeding, intestinal blockage, gut narrowing and difficulty swallowing. It notes that linseed contains cyanide-forming compounds at 20 to 50 mg cyanide per 100 g, and that neither a single 100 g dose nor 45 to 50 g daily for 4 to 6 weeks caused signs of intoxication in people. It advises against use under age 12, during pregnancy and breastfeeding for lack of data, and in women with hormone-dependent tumors because investigations in healthy women suggest an estrogenic effect.

Where it meets prescription medicines

The EMA monograph says absorption of other medicines taken at the same time may be delayed by linseed, so doses should be taken half an hour to an hour apart. To lower the risk of intestinal obstruction, linseed should be used with medicines that slow the gut, such as opioids and loperamide, only under medical supervision. The monograph also notes an estrogenic effect in healthy women, which is why it advises against use with hormone-dependent tumors.

Medicines the site’s own interaction rules flag with flaxseed

The quiz applies these rules when someone names a medicine. They come from published interaction references and are a reason to ask a pharmacist, not a diagnosis:

Catalog entries that list flaxseed

If you want flaxseed in a product rather than as a loose herb, these are the entries that carry it, with the label amounts and the reviews read.

Spectrum Organic Ground Flaxseed 4.7 out of 5 from 40,684 ratings from Amazon · $0.25 a day Pure for Men Original Vegan Cleanliness Stay Ready Fiber Supplement 4.5 out of 5 from 16,160 ratings from Amazon · ~$0.50 a day at a 2-capsule starting dose; the label allows building up to 4-6 capsules Amazing Grass Greens Blend Superfood, The Original 4.7 out of 5 from 6,672 ratings from iHerb · $0.89 a day Soothe Naturals Soothe & Renew 4.7 out of 5 from 255 ratings from soothenaturals.co · $1.33 per day at one tablespoon; the brand says one to two

Is a flaxseed product right for you?

The quiz takes about three minutes, asks what you have tried and which medicines you take, and shows the products whose trials and labels fit, with the reasons.

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Herbs that sit beside it

Ayurvedic / Western Psyllium Plantago ovata Western Slippery elm Ulmus rubra Western Marshmallow root Althaea officinalis Ayurvedic / Western Senna Senna alexandrina (Cassia senna, Cassia angustifolia)

Questions people ask

Does flaxseed work for constipation?

In a 90-person trial, 50 g a day of flaxseed flour raised weekly bowel movements from 2 to 7 over 4 weeks, against 2 to 6 on lactulose. There was no placebo group, and the other positive trials come from one group working with people who have diabetes.

Did flaxseed help irritable bowel syndrome?

In a 40-person pilot, two tablespoons of whole or ground linseed a day for 4 weeks did not significantly improve symptom severity against no linseed (P=0.12 and P=0.10). Stool frequency and consistency did not change either.

Does flaxseed oil do the same as the seed?

Not necessarily. The laxative effect is attributed to the seed’s mucilage and fiber, and the oil carries almost none of it.

Is the cyanide in flaxseed a problem?

The EMA monograph reports 20 to 50 mg cyanide per 100 g in linseed and notes that neither a single 100 g dose nor 45 to 50 g a day for 4 to 6 weeks caused intoxication signs in people. It still advises against use in pregnancy and under age 12 because of limited data.

How much water does flaxseed need?

The EMA monograph says to take each dose with at least 150 ml of water or similar fluid. Without enough fluid the seed can swell and block the throat or gut.

Sources