Yeast-leavened oat breads with high or low molecular weight beta-glucan do not differ in their effects on blood concentrations of lipids, insulin, or glucose in humans

Increased intestinal viscosity appears to be the major mode of action by which dietary oat P-glucan increases the fecal excretion of bile acids and thereby lowers blood cholesterol concentrations. The objective of this experiment was to investigate whether there is a difference in effects on blood lipids between two yeast-leavened oat bran breads containing beta-glucan (6 g/d) of low or high average molecular weight (HMW) (217 or 797 kDa, respectively). The breads were fed to 22 volunteers (women, n = 11; men, n = 11) in a randomized, double-blind, crossover design. The participants ate one bread for 3 wk as part of their normal diet and switched breads after a 2-wk washout period. Blood samples were drawn from fasting subjects and analyzed for lipids, insulin, glucose, and alpha- and gamma-tocopherol. The two experimental oat breads did not differ in their effects on any of the variables measured. Compared to baseline, however, consumption of HMW bread increased serum insulin by 22.6% (P < 0.03) and decreased blood glucose concentrations by 3.4% (P < 0.05). These results suggest that the molecular weight, when beta-glucan is consumed in oat bran breads as part of the habitual diet, does not play an important physiological role in moderately hypercholesterolemic humans.