Abstract
Rye and flax are important sources of dietary phytoestrogens, the intake
of which results in increased urinary and plasma enterolactone levels.
Enterolactone levels in plasma have been associated with the reduced risk of
breast cancer and acute coronary events. Furthermore, lignan-rich diets have
shown inhibition of colon cancer growth in animal trials. Enterodiol and
enterolactone are formed by bacterial flora in the colon from several
precursors from rye, and mainly from secoisolariciresinol from flax.
Enterodiol formation occurs concomitantly with the carbohydrate consumption,
whereas subsequent enterolactone conversion is a slower process. Plant lignans
are attached to the fibre matrix. As carbohydrates are degraded in the colon,
lignans are liberated to be available for colonic bacteria.
In the present study enterodiol and enterolactone formations from rye and flax
were compared using an in vitro fermentation model (Karppinen et al. 2000).
The samples were digested enzymatically prior to the fermentation with human
faecal flora. Compared to rye flax carbohydrates were degraded to a lower
extent. Also, only 45 % of secoisolariciresinol was converted to enterodiol,
which was subsequently oxidized to enterolactone completely. This can be
explained by several layers of seed coat in flax making the matrix rigid and
slowly fermentable.
Carbohydrate components of rye are cellulose, arabinoxylans, glucans and
fructans and they contain also soluble, easily fermentable polysaccharides.
Even though the amount of plant lignans is lower in rye than in flax seed, the
bioavailability of enterolactone precursors is fairly good due to its easily
fermentable carbohydrate matrix. Therefore, enterolactone formation can be
detected in vivo (Juntunen et al. 2000). More work is needed to fully confirm
all the enterolactone precursors in rye. Even though seed structure of flax
affects strongly the bioavailability of plant lignans, the abundance of
secoisolariciresinol makes flax an excellent source of enterolactone
precursors.
References
Karppinen S, Liukkonen K, Aura, A-M, Forssell P, Poutanen K (2000) J. Sci.
Food Agric. 80: 1469-1476
Juntunen KS, Mazur WM, Liukkonen KH, Uehara M, Poutanen KS, Adlercreutz HCT,
Mykkanen, HM (2000) Br. J. Nutr. 84: 839-846
Original language | English |
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Title of host publication | International Meeting, Phytochemistry and Biology of Lignans |
Publication status | Published - 2003 |
Event | International Meeting: Phytochemistry and Biology of Lignans - Conference Center 'Cloister St. Albert', Bornheim-Walberberg, Germany Duration: 6 Apr 2003 → 9 Apr 2003 |
Conference
Conference | International Meeting |
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Country/Territory | Germany |
City | Bornheim-Walberberg |
Period | 6/04/03 → 9/04/03 |