Flaxseed contains soluble fiber, like that found in oat bran, and may have a laxative effect.
Studies of flaxseed preparations to lower cholesterol levels report mixed results. A 2009 review of the clinical research found that cholesterol-lowering effects were more apparent in postmenopausal women and in people with high initial cholesterol concentrations.
Some studies suggest that alpha-linolenic acid (a substance found in flaxseed and flaxseed oil) may benefit people with heart disease. But not enough reliable data are available to determine whether flaxseed is effective for heart conditions.
Study results are mixed on whether flaxseed decreases hot flashes.
Although some population studies suggest that flaxseed might reduce the risk of certain cancers, there is not enough research to support a recommendation for this use.
NCCAM is funding studies on flaxseed. Recent studies are looking at its potential role in preventing or treating atherosclerosis (hardening of the arteries), breast cancer, and ovarian cysts.