Barley for Food and Health: Science, Technology, and Products

GLYCEMIC RESPONSE TO CARBOHYDRATE CONSUMPTION 189
consistometer, which is a measure of the distance a fluid flows in a given time
interval. In this study, PW barley flour, previously studied by this group, was
prepared into bread at different concentrations. Glycemic responses followed the
trend of increasing β-glucan content, with a minimum GI value of 52.3 compared
with 100 for white wheat bread. The fluidity index values were highly correlated
with GI values of the entire range of breads. Interestingly, in this study the palatability
of the barley test breads was preferred by the test subjects. The fluidity
measurement technique offers a relatively simple tool for evaluating glycemic
properties of a food enriched with viscous fiber. Earlier methodology reports by
the Lund group were measurement of gastric emptying rate by ultrasonography
(Garwiche et al. 2001) and use of an in vitro procedure based on chewing to
predict metabolic responses (Granfeldt et al. 1992).
Studies Using Subjects with Diabetes
Shukla et al. (1991) compared the glycemic response of barley chapatis in both
healthy subjects and those with type 2 diabetes. A 50-g carbohydrate serving of
chapati was consumed by each subject followed by glycemic and insulinemic
response measures. The GI for barley chapati was 68.7 in healthy subjects and
53.4 for those with diabetes. The researchers observed a higher insulinemic index
in diabetic subjects than in healthy subjects, suggesting higher mobilization of
insulin. Pick et al. (1998) incorporated waxy hulless barley flour into a variety
of breads, pasta, muffins, and cookies, some of which included cracked barley
grain. The subjects with type 2 diabetes consumed eight servings daily of the
barley products, containing 15 g of carbohydrate per serving, for a 12-week
period. Each subject served as his own control, consuming white wheat bread
for an equivalent period. Mean total dietary fiber intake was 18 g per day in the
control period and 39 g per day in the barley period. Mean glycemic response
(AUC) was lower, and insulin response area was higher, for barley foods than
for white bread. The higher postprandial serum insulin response was of particular
interest, since other studies with soluble fiber had resulted in variable effects on
insulin levels. The barley bread products were reported to be very palatable to
subjects, and the authors also reported that some subjects reduced their dose of
oral hypoglycemic drugs while in the barley period.
Rendell et al. (2005) compared breakfast meals of PW barley flakes and oatmeal
for glycemic response in patients with and without diabetes. A low-fiber
liquid meal replacer (LMR) was used as a reference standard. A substantial reduction
in the postprandial glycemic peak following ingestion of the PW barley was
observed as compared to LMR or oatmeal. Insulin response following PW was
dramatically lower than either oatmeal or LMR, prompting researchers to calculate
glucose/insulin ratios (G/I), which were found to be lowest for LMR and
highest for PW. The G/I ratios of diabetic subjects were consistently higher than
those of the nondiabetic subjects. These researchers commented that glycemic
responses from PW barley were similar to those observed in diabetic patients
treated with α-glucosidase, a drug used to block carbohydrate digestion and
absorption. In Japan, Hinata et al. (2007) reported markedly improved diabetes