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

BARLEY AND HEART DISEASE 183
of foods to be consumed are all variables. In addition, the selection of subjects,
sample size, dose of treatment, and dietary control of subjects may influence the
results. Therefore, there are some inconsistencies and conflicting results reported
in early clinical studies using extracted β-glucans.
Keogh et al. (2003) investigated the effects of a concentrated barley β-glucan
product (Glucagel) incorporated into foods consumed by hypercholesterolemic
men over four weeks. Compared to a control period, there were no significant
changes in total cholesterol and other blood lipids, although subjects consumed
8to11.9gofβ-glucan per day. The authors concluded that structural changes
might have occurred in the β-glucan during extraction or storage. Björklund et al.
(2005) incorporated β-glucan fractions from oats and barley into fruit-flavored
beverages to provide a daily intake of 5 or 10 g of β-glucan from either grain. A
total of 89 hypercholesterolemic men and women at two sites consumed the beverages
for a five-week period. Compared to controls, 5 g of β-glucan from oats
significantly lowered total cholesterol, but there was no effect on serum lipids by
either 10 g of oat or either level of barley β-glucan. These inconsistent results
were attributed to differences in molecular weight and/or solubility of β-glucans
due to processing. These two studies indicate the necessity for careful evaluation
of products intended for use in functional foods. However, Naumann et al.
(2006) demonstrated effective lowering of total and LDL cholesterol in healthy
subjects who consumed a fruit drink enriched with oat β-glucan. Keenan et al.
(2007) reported use of concentrated β-glucanextractfrombarleytolowerLDL
cholesterol in hyperlipidemic subjects. Because of prior reports on the influence
of the molecular weight of β-glucan preparations on viscosity and possible nonefficacy,
two products, of high and low molecular weight (HMW and LMW),
were used in the study. The β-glucan extracts were tested at daily doses of 3
and 5 g, incorporated into juice and cereal. After six weeks of treatment, LDL
cholesterol levels fell by 15% in those consuming 5 g of HMW, 13% in those
consuming 5 g of LMW, and 9% when both groups consumed 3 g of β-glucan
per day. The researchers concluded that molecular weight did not significantly
influence efficacy in this study, although the LMW product had improved sensory
properties and might have greater applicability in food products. In two
experiments on β-glucan from oat bran (Kerckhoffs et al. 2003), there were differences
in the results based on the food vehicle used to administer the products.
Subjects fed bread and cookies providing 5 g of β-glucan daily for four weeks
had no significant change in total or LDL cholesterol. After a washout period,
thesamesubjectsconsumed5gofthesameproduct per day in orange juice, and
their cholesterol levels were decreased significantly. These authors concluded
that the processing of baked products may have had a detrimental effect on
cholesterol-lowering properties of the β-glucan, but the molecular weight did not
appear to be a factor. At this point, there are insufficient data on the effects
of processing to draw meaningful conclusions on the influence of processing,
baking, or cooking on the efficacy of extracted β-glucan on blood lipid composition.
The variability of outcomes in studies using β-glucan reinforces the
importance of standardization of extraction procedures, as cited by Brennan and
Cleary (2005).