Variability in Anticancer Lignan Levels in Flaxseed.
Variability in Anticancer Lignan Levels in Flaxseed.
Year: 1997
Authors: L U Thompson, S E Rickard, F Cheung, E O Kenaschuk, W R Obermeyer.
Publication Name: Nutr. Cancer.
Publication Details: Volume 27; Number 1; 26.
Abstract:
Flaxseed and its major mammalian lignan precursor SDG have been shown to be protective against chemically induced carcinogenesis in animal models. Previous research by these investigators indicated that flaxseed is the richest source of mammalian lignan precursors. However, it is not known whether these lignan levels vary with the source of flaxseed. The objective of this study was to determine if lignan levels in flaxseed are affected by variety of seed, growing location, harvest year, and seeding time. Ten varieties of flaxseed (AC Linora, Andro, Flanders, Linott, McGregor, Noralta, NorLin, NorMan, Somme, and Vimy) were subjected to 1) in vitro fermentation with human fecal inoculum for 24 hours under anaerobic conditions to assess mammalian lignan production, a method which has been shown to correlate well with urinary lignan excretion in rats and humans, and 2) HPLC analysis for secoisolariciresinol levels. Three of these varieties (Linott, McGregor, and NorLin) were grown in four locations, seeded early (May) for three different years, and, in one year, seeded early (May) or late (June). Significant differences in lignan production were observed among the different varieties, ranging from 0.96 ?mol/g for Linott to 3.15 ?mol/g for Somme flaxseed. Growing location also had a significant effect on lignan production from all three varieties. Harvest year significantly affected only the Linott variety, whereas seeding time had no effect. A significant correlation was observed between lignan values obtained from HPLC and in vitro fermentation methods, indicating that HPLC analysis of flaxseed may be used as a predictor of its lignan production levels. Variability in the content of soybean isoflavonoids has also been reported due to soybean variety, harvest location and harvest year. The authors speculate that environmental stress during growth may play a role in the level of lignan precursors produced. Despite the variability in lignan levels noted between flaxseed varieties, the authors indicate that flaxseed is an excellent source of lignans since even the lowest levels noted surpass those of the next richest lignan source, lentils, which typically have levels of 0.06 ?mol/g. The authors recommend that differences due to variety, harvest location, and harvest year of flaxseed should be taken into consideration when carcinogenesis studies are designed.
