Over the thousands of years it’s been cultivated, flaxseed has had a variety of health and industrial uses. Around 500 B.C., Hippocrates wrote about flaxseed being a laxative, and pioneers in North America made flaxseed dressings for cuts and burns. Fiber from the plant is made into linen, and oil from the seed is used in paints, among other products.
Today, flaxseed and flaxseed oil are used as dietary supplements for constipation, diabetes, cholesterol, cancer, and other conditions.
Flaxseed is made into tablets, extracts, powder, and flour. The oil is also put in capsules.
Flaxseed contains fiber, which generally helps with constipation. However, there’s little research on the effectiveness of flaxseed for constipation.
Studies of flaxseed and flaxseed oil to lower cholesterol levels have had mixed results. A 2009 research review found that flaxseed lowered cholesterol only in people with relatively high initial cholesterol levels.
Flaxseed doesn’t decrease hot flashes, studies from 2010 and 2012 suggest.
NCCIH is funding preliminary research on the potential role of substances in flaxseed for ovarian cancer, cardiovascular disease, metabolic syndrome, diabetes, asthma, and inflammation.
Don’t eat raw or unripe flaxseeds, which may contain potentially toxic compounds.
Flaxseed and flaxseed oil supplements seem to be well tolerated in limited amounts. Few side effects have been reported.
Avoid flaxseed and flaxseed oil during pregnancy as they may have mild hormonal effects. There’s little reliable information on whether it’s safe to use flaxseed when nursing.
Flaxseed, like any fiber supplement, should be taken with plenty of water, as it could worsen constipation or, in rare cases, cause an intestinal blockage. Both flaxseed and flaxseed oil can cause diarrhea.