Flaxseed

Linum usitatissimum · Flaxseed oil · Linseed · Flax seed

Snapshot

Indications	Contraindications
Blood pressure¹ Lipid profile² Glycemic control³ Constipation⁴ Perimenopausal symptoms⁵ Inflammatory markers⁶ Fatty liver disease⁷	Intestinal obstruction or ileus⁴ Difficulty swallowing⁴ Hormone-dependent tumours⁴ Flaxseed hypersensitivity⁴

Flaxseed (Linum usitatissimum) is a seed supplying alpha-linolenic acid (ALA), an omega-3 fatty acid, plus lignans and soluble fiber, and is also sold as oil⁸. Fiber supports stool bulk and lignans act as weak phytoestrogens⁹. It is used for cardiometabolic risk factors, constipation, and menopausal symptoms, mostly by adults with elevated cardiometabolic risk.⁹

Glucose benefit was confined to whole seed, not oil or lignan extract¹⁰. The European Medicines Agency (EMA) herbal monograph lists well-established use for habitual constipation⁴. One placebo-controlled trial reported fewer perimenopausal symptoms⁵. A 2022 laboratory fermentation model found flaxseed preparations shifted gut microbiota and released lignan metabolites; the finding is not from a human trial¹¹. Products listing flaxseed number over two thousand, mostly oil softgels alongside ground seed and powders; see Form comparison.

The EMA monograph attributes the main caution to swelling: without adequate fluid the seed can block the throat or bowel⁴. It also asks that other medicines be taken half an hour to an hour apart, since absorption may be delayed⁴.

Last updated October 15, 2026. Read how we make monographs.

In the full monograph

66 sources, 61 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources