Linseeds are also known as flaxseeds, although sometimes the names are used for different varieties of Linum usitatissimum – the flax grown for its fibre and linseed grown for its seeds. Linseed varieties grown for their seed have shorter stems with lower fibre content, making them easier to harvest.
The seeds are rich in protein and oil, and also contain lignan (secoisolariciresinol diglucoside or SDG), a phytoestrogen compound with antioxidant properties, and soluble fibre, which is described as mucilage. When boiled, the seeds produce a jelly-like substance from the soluble fibre. The seeds are low in starch and sugar.
About 40% of the seed is oil, which can be extracted via solvent or mechanical pressing methods. The oil is the richest vegetable source of the essential omega-3 fatty acid (FA) alpha-linolenic acid.
Linseeds contain about 20% protein. The meal – after oil extraction – is the richest source of protein. The oil does not supply any protein, but is the richest source of energy and of omega-3 FA. Oil is relatively pure so will not contain lignan or soluble fibre.
Linseeds contain about 10 mg of copper and 0.26 mg selenium per kilo and 4 g magnesium, but have an inverse calcium to phosphorus ratio for horses, with about 2.6 g calcium and 6.6 g phosphorus per kilo. The oil does not contain any minerals, but is richer in vitamin E than the seeds, at 171 mg per kilo, compared to 50 mg/kg in the seeds.
When eaten by women, linseeds appear to reduce the risk of breast cancer and mortality rates in women affected by breast cancer. It also seems to reduce cardiovascular disease risk in men and women. Linseed oil inhibits inflammatory mediators, probably via its omega-3 FA content.
Linseed was traditionally used as a conditioning feed for horses, boiled for many hours before being fed with cereals, chaff and/or bran. The extra protein and fats it contains would have upgraded unbalanced diets of forage and cereals. Nowadays, precooked linseeds are available so that the seeds do not have to be boiled. Micronization removes the anti-nutritional factors and cyanide-producing capacity making the processed seeds safe to feed.
Researchers have shown a decrease in itching and improvement in the coat of horses affected by sweet itch who were fed micronized linseed, and this was probably due to the omega-3 FA content. Feeding both the whole micronized linseed and the oil together will give the best benefits of lignans, soluble fibre and omega-3 FA, and feeding the meal is best for extra protein.