Food-Based Ingredients to Modulate Blood Glucose - Advances in Food and Nutrition Research - page 194

absorption ( Lazaridou & Billaderis, 2007; M¨kel¨inen et al., 2007 ). The effi-
cacy of b -glucan as a potential functional food ingredient may be related to
its structure, molecular weight, and rheological characteristics, which in turn
can be affected by cooking and storage ( Aman, Rimsten, & Andersson,
2004; Andersson et al., 2004 ). The use of barley b -glucan in foods with high
GI could result in lowering the glycemic response and maintaining healthy
blood glucose levels in people with IGT. However, the long-term effects of
barley b -glucan on fasting blood glucose and HbA1c levels need to be tested
to substantiate its role in maintaining healthy blood glucose levels.
Cereal test meals with 0, 1, or 2 g b -glucan from barley were tested in
overweight men and women ( Kim, Behall, Vinyard, &Conway, 2006 ). The
2g b -glucan test meals showed a significant lowering of glucose Area under
the curve (AUC) in women only with no difference in the glycemic
response of men. The authors did not explain the mechanism involved
and suggested that unlike in men, a higher dose of b -glucan may be required
to see a significant difference in postprandial glycemia. Barley and rye kernels
as breakfast cereals have also been shown to reduce blood glucose postpran-
dially and then for the whole day showing second meal effect ( Nilsson,
¨ stman, Granfeldt, & Bj¨ rck, 2008 ). In this study, they were compared
with white bread, wheat kernels, oat kernels, whole-grain barley flour por-
ridge, and white bread with barely dietary fiber. The beneficial effects of bar-
ley and rye kernels on the whole-day glucose tolerance were due to the
high-fiber and indigestible starch content of those test meals, due to the pres-
ence of both soluble and insoluble fiber and also due to the specific food
form in the form of kernels.
In countries like Japan where high-GI food such as rice is used as a staple,
mixing barley is a viable strategy to reduce the blood glucose response to
meals. Sakuma et al. (2009) tested white rice mixed with 30% and 50% bar-
ley along with pure white rice and pure barley meals equivalent to 75 g avail-
able carbohydrate. The glucose and insulin areas under the curve were
decreased dose-dependently using the barley-mixed rice meals that the
authors attributed to the viscous soluble fiber content in barley. However,
this is surprising given that the total dietary fiber content was only between
3% and 10% for the barley-based meals and studies using pure barley
b -glucan has shown efficacy at 3% or above concentration. Hence, it
may be assumed that the efficiency of b -glucan varies when it is in barley
grain compared to when it is extracted and purified.
Although high viscosity is usually reported to be responsible for the effi-
cacy of barley b -glucan, some studies have reported the successful use of