Flax Seeds (linseeds) contain high amounts of the essential fatty acid alpha linolenic acid (ALA, C18:3 (n-3)). This fatty acid is the parent compound for production of the series 3 eicosanoids, a group of short lived hormones that regulate important cellular functions including inflammation. Flax seeds are unusual because they are one of the few foods that contains more omega-3 fatty acids than omega 6-fatty acids, and this makes them useful in rebalancing the omega-3 to omega-6 fatty acid ratio. The Western diet for example contains too many omega-6 fatty acids and far too few omega-3 fatty acids and this creates an unbalanced eicosanoid production, which is a primary driver of inflammation and disease. Recommendations to eat flax seeds are therefore often based on their unique fatty acid profile.
However, there is more to flax seeds than the fatty acid profile they contain. Flax seeds are an excellent source of dietary fibre and this may account for some of their health benefits. In addition, the fibre component of flax seeds is associated with a group of polyphenolic compounds called the lignans. These lignans are thought to have particular health effects in humans which may relate to their phyto-oestrogen activity. This ability to interact with the oestrogen receptor may explain the anti-cancer effects of flax seed consumption. This is because flax seed consumption has been shown to reduce oestrogen levels in women and may be able to cause a shrinkage of breast cancer tumours. Of course the tough outer seed coat of flax seeds is indigestible to humans and so milling the seeds is necessary in order to release their nutrients for digestion.