A source of fiber for linen fabric since ancient times, the slender flax plant (Linum usitatissimum) also boasts a long history as a healing herb. First cultivated in Europe, the plant’s brown seeds were regularly used to prepare balms for inflamed skin and healing slurries for constipation. Today, flaxseeds–also called linseeds–are best known for the therapeutic oil that is derived by pressing them. Rich in essential fatty acids, or EFAs, flaxseed oil has earned a solid reputation for treating a range of ailments, from heart disease to lupus.