Food-Based Ingredients to Modulate Blood Glucose - Advances in Food and Nutrition Research - page 196

Addition of other ingredients such as lactic acid has shown further ben-
efits on day-long glucose tolerance. Ostman, Liljeberg Elmst˚hl, and Bjorck
(2002) compared standard barley bread with a barley bread containing lactic
acid in healthy subjects. They tested the glycemic response to a standard
high-GI lunch after 4 h of consuming this low-GI breakfast. The results
showed a significant reduction in glycemic and insulin response after the
lunch following the barley bread with lactic acid. This showed the ability
of lactic acid to lower glycemic response to a second meal. This may be
in addition to the postprandial glycemic lowering effect after the breakfast
although the authors did not measure it.
Not all studies using barley b -glucan have demonstrated a lowering of
glycemic response ( Keogh et al., 2003; Smith, Queenan, Thomas,
Fulcher, & Slavin, 2008 ). Differences in molecular weight and degree of
purity of b -glucan have demonstrated contradictory results in glycemic
response studies. In a randomized controlled trial, healthy human subjects
consumed unleavened Indian flatbreads called chapatis containing high-
molecular weight barley b -glucan at doses of 0, 2, 4, 6, and 8 g on different
occasions ( Thondre &Henry, 2009 ) . The incremental area under the glucose
curve values for all the five different types of chapatis were significantly low
( P < 0.001) compared with reference food glucose. The GI values of chapatis
with 4 and 8 g b -glucan were 43-47% lower (GI, 30 and 29, respectively)
compared with chapatis without b -glucan (GI, 54). In another trial using
a similar study design, healthy subjects who consumed flatbreads with a
low-molecular-weight high-purity b -glucan did not show any significant
difference in their blood glucose response ( Thondre &Henry, 2011 ) . Further
in vitro studies investigating the mechanisms behind the above-mentioned
glycemic response effects highlighted the role of this specific high-molecular
weight-soluble dietary fiber in slowing down the particle breakdown of
starchy foods such as flatbreads ( Thondre, Monro, Mishra, & Henry,
2010 ). There was an inverse relation between the rate of in vitro starch diges-
tion and amount of b -glucan in chapatis. The rate of starch digestion was
influenced by the ability of chapatis to resist particle breakdown. This prop-
erty along with the increase in viscosity of the food bolus was found respon-
sible for the glycemic response effects of high-molecular weight barley
b -glucan. The effect of high-purity barley b -glucan with low molecular
weight was also tested on in vitro starch digestibility of chapatis. There was
no significant difference in the amount of glucose released after in vitro
digestion or in the glycemic response to chapatis with 0, 4, and 8%
b -glucan ( P > 0.05). It may be concluded that

low-molecular-weight