Oral presentation at WCOF 2020

Flaxseed’s health benefits are attributed to high levels of alpha linolenic acid (ALA), soluble fibre and lignans (mainly secoisolariciresinol diglycoside (SDG)). However, flaxseed also contains vitamin B6 antagonists (linatine, 1-amino D-proline) and cyanogenic glycosides (linustatin, neolinustatin). Our clinical trial found that consumption of 20g and 30g ground flaxseed negatively affected B6 status providing an impetus to determine if the beneficial bioactives can be separated from the anti-nutrients to produce real health benefits. We postulated that if the health promoting bioactives (fibre, SDG) are concentrated in the hull, while the anti-nutrients (linatine, cyanogenic glycosides) are concentrated in the meal, de-hulling would separate the two. We evaluated ground flaxseed (n=4), Flax50 (50% de-hulled, n=4), Flax70 (70% de-hulled, n=4), and hull (n=1) for: cyanogenic glycosides as hydrogen cyanide (HCN)-equivalents by GC-MS; linatine by NMR; ALA by GC; SDG by HPLC; fibre using AOAC 2011.25.
Hulls had 60% and 73% higher levels of HCN-equivalents, but 42% and 48% lower levels of linatine compared to Flax50 and Flax70, respectively. SDG levels were 360% and 753% higher and soluble fibre was 169% and 332% higher in hulls compared to Flax50 and Flax70, respectively. Oil (%) in hulls was 41 and 45% lower, but ALA (% of total fatty acids) was only 3% lower in hulls compared to de-hulled flax products.
Further processing (ie. Heating) may reduce the level of HCN-equivalents in the hull. Hulls should be tested in human feeding trials to determine if linatine has been lowered sufficiently to avoid health problems.