Linseed as a Functional Food for the Management of Obesity

Linseed has been cultivated for at least 8000 years and is now a major oilseed crop in many countries. The major components with potential therapeutic uses are the essential n-3 fatty acid, α-linolenic acid (ALA), lignans such as secoisolariciresinol diglucoside (SDG) and carbohydrates such as mucilages containing arabinoxylans. ALA is orally bioavailable and may be stored or converted into longer-chain n-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and other bioactive lipid metabolites. In most studies in humans, whole linseed improves insulin sensitivity, linseed flour but not oil attenuates the pro-inflammatory state and linseed oil but not the lignan fraction benefits osteoporotic bone in obese or overweight patients. SDG is metabolised in the intestine to the mammalian lignans, enterodiol and enterolactone. Treatment with SDG may improve metabolic parameters, decrease the progression of atherosclerosis and protect the heart, liver and kidneys but does not seem to decrease obesity or blood pressure. The fibre present in linseeds may improve gastrointestinal function. Thus, there is considerable evidence that the constituents of linseed, especially ALA and probably SDG and fibre to a lesser extent, either separately or combined, can be defined as a functional food as they improve the multi-organ changes induced by obesity. However, the patient groups that will benefit most still need to be defined, and this may also be helped by a clearer definition of the molecular mechanisms.