Key Findings
This is one of the earliest studies of the health and safety effects of flaxseed. A large amount of flaxseed (50 g/day) was found not to increase lipid peroxidation products such as malondialdehyde (MDA) or cyanogenic glycosides (linustatin, neolinustatin and linamarin) in baked products. Flaxseed was hypoglycaemic and reduced serum cholesterol while raising omega 3 fatty acids in serum and erythrocyte lipids. Flaxseed was hypocholesterolaemic in this group of normocholesterolaemic female subjects, with the effect being mainly on LDL. HDL and TG were unchanged after the 4-week flaxseed supplementation period. It is not clear whether the ALA or mucilage in the flaxseed was responsible for lowering serum cholesterol.
ABSTRACT
Although high a-linolenic acid flaxseed (Linum usitatissimum) is one of the richest dietary sources of a-linolenic acid and is also a good source of soluble fibre mucilage, it is relatively unstudied in human nutrition. Healthy female volunteers consumed 50 g ground, raw flaxseed/d for 4 weeks which provided 12-13% of energy intake (24-25 g/100 g total fat). Flaxseed raised a-linolenic acid and long-chain n-3 fatty acids in both plasma and erythrocyte lipids, as well as raising urinary thiocyanate excretion 2.2- fold. Flaxseed also lowered serum total cholesterol by 9 % and low-density-lipoprotein-cholesterol by 18 %. Changes in plasma a-linolenic acid were equivalent when 12 g a-linolenic acid/d was provided as raw flaxseed flour (50 g/d) or flaxseed oil (20 g/d) suggesting high bioavailability of a-linolenic acid from ground flaxseed. Test meals containing 50 g carbohydrate from flaxseed or 25 g flaxseed mucilage each significantly decreased postprandial blood glucose responses by 27 %. Malondialdehyde levels in muffins
containing 15g flaxseed oil or flour/kg were similar to those in wheat-flour muffins. Cyanogenic glycosides (linamarin, linustatin, neolinustatin) were highest in extracted flaxseed mucilage but were not detected in baked muffins containing 150 g flaxseed/kg. We conclude that up to 50 g high-a-linolenic acid flaxseed/d is palatable, safe and may be nutritionally beneficial in humans by raising n-3 fatty acids in plasma and erythrocytes and by decreasing postprandial glucose responses.