Agriculture Reference
In-Depth Information
matairesinol, lariciresinol, pinoresinol, and syrin-
garesinol. Plant lignans are found in a wide variety
of plant foods including fl ax (
Linum usitatissimum
L.) seed, whole grains [maize, oat, wheat, and rye
(
Secale cereale
L.)], legumes, fruits, and vegeta-
bles (Thompson et al., 1991). Qu et al. (2005)
reported a range of secoisolariciresinol content
from undetectable to 83 μg g
−1
in the wheat cul-
tivars studied. When consumed, plant lignans
such as secoisolariciresinol and matairesinol are
converted to the mammalian lignans, enterodiol
and enterolactone, by intestinal microfl ora in
humans.
The mammalian lignans, enterodiol and entero-
lactone, have strong antioxidant activity and weak
estrogenic activity that may account for their bio-
logical effects and health benefi ts (Thompson
et al., 1991, 1996; Wang et al., 1994) and make
them unique and very useful in promoting health
and combating various chronic diseases. Entero-
diol and enterolactone may protect against heart
disease and hormone-related breast and prostate
cancers (Adlercreutz and Mazur 1997; Johnsen
et al., 2004). They may inhibit colon cancer cell
growth and induce cell cycle arrest and apoptosis
in vitro
(Qu et al., 2005). Lower cancer rates have
been associated with high intakes of dietary
lignans (Adlercreutz and Mazur 1997). In a
Danish study that followed 857 postmenopausal
women, those eating the highest amounts of whole
grains had signifi cantly higher blood levels of
enterolactone (Johnsen et al., 2004). Blood levels
of enterolactone were inversely related to cardio-
vascular-related and all-cause death in Finnish
men (Vanharanta et al., 2003), suggesting the pro-
tective effects of lignans against such conditions.
effects of β-glucan include lowering blood choles-
terol level, controlling blood sugar, and enhanc-
ing the immune system.
The regulating effects of β-glucan on blood
cholesterol and sugar levels probably relate to its
high viscosity property as a soluble fi ber to bind
cholesterol and bile acids and to facilitate their
elimination from the body. β-Glucan is the main
component responsible for the cholesterol-lower-
ing effect of oat bran (Wood 1990; Davidson
et al., 1991; Braaten et al., 1994b; Bell et al., 1999).
Results from studies using either oat- or yeast-
derived β-glucan show typical reductions of 10%
for total cholesterol and 8% for LDL cholesterol
after 4 weeks of use. This was accompanied by up
to a 16% elevation in HDL cholesterol (Uusitupa
et al., 1992; Behall et al., 1997; Bell et al., 1999).
The FDA has approved the health claim that con-
sumption of about 3 g day
−1
of β-glucan soluble
fi ber lowers blood cholesterol levels (FDA 1997).
β-Glucan had an effect in controlling blood sugar
in diabetic subjects, and was helpful in reducing
the elevation in blood sugar levels after a meal,
probably by delay of gastric emptying, allowing
dietary sugar to be absorbed more gradually, or
by possibly increasing the tissue sensitivity to
insulin (Braaten et al., 1994a; Pick et al., 1996).
Phytosterols
Phytosterols are a collective term for plant sterols
and stanols, which are similar in structure to cho-
lesterol but differ in their side-chain groups. Plant
sterols have a double bond in the sterol ring, while
plant stanols lack a double bond in the sterol ring.
The most common plant sterols are sitosterol,
campesterol, and stigmaterol, and the most
common plant stanols are sitostanol, campestanol,
and stigmastanol.
Plant sterols and stanols are white crystalline
powders with restricted lipid solubility. Esterifi -
cation of plant sterols and stanols makes them
more lipid-soluble with properties similar to those
in normal edible fats and oils. The esterifi ed forms
can be easily incorporated into foods such as mar-
garines and salad dressings. Upon intake, the
ester is cleaved by lipases in the small intestine,
b
-Glucan
β-Glucan is a group of linear polymers of glucose
molecules connected by a 7 : 3 ratio of β-(1-4)-
and β-(1-3)-linkages. Compared to cellulose with
only β-(1-4)-linkages, the β-(1-3)-linkages inter-
rupt β-(1-4)-linkages to make β-glucan more
fl exible, soluble, and viscous. β-Glucan is com-
monly found in cell walls of many grains, such as
oat, barley, and wheat. The major biological
