Flax (Linum usitatissimum) is a food and fiber crop. Flaxseeds are a good source of dietary fiber and omega-3 fatty acids, including alpha-linolenic acid.

Flaxseeds also contain phytoestrogens called lignans, which are similar to the hormone estrogen. The fiber in flaxseed is found in the seed coat. When taken before eating, it seems to make people feel less hungry. It might also help limit how much cholesterol the body absorbs from food.

Flaxseed is used for constipation, diabetes, high cholesterol, obesity, and swelling of the kidneys in people with lupus. It is also used for many other conditions, but there is no good scientific evidence to support most of these other uses.

Flaxseed and flaxseed oil have different effects. For information about the oil, see Flaxseed Oil.